Terminology of Skin Lesions (Primary & Secondary Morphology)

• Pages: 16
• Epigraph: "You see, but you do not observe" — Holmes to Watson in Scandal in Bohemia, by Arthur Conan Doyle, 1892

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• A patient and thorough approach to evaluation decreases the risk of making an incorrect diagnosis or overlooking another diagnosis
• Knowledge and appropriate use of dermatological terminology are fundamental
• Recognition of disease patterns requires repeated patient encounters
• The history is indispensable in elucidating complex diagnoses
• The entire mucocutaneous surface, as well as the hair and nails, should be examined whenever reasonable
• Morphologic characteristics derived from cell type in skin must be carefully scrutinized
• Diseases have characteristic morphology and distribution
• Common pitfalls in dermatologic diagnosis exist and can be avoided

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• Diagnosis and treatment of skin diseases rest on the physician's ability to use the language of dermatology
• Must recognize primary and sequential lesions of the skin
• Must recognize the various patterns in which lesions occur
• The "dermatology lexicon" = standard terminology for dermatologic description
• Standard terminology is the first step in generating a differential diagnosis
• Example: a pearly, flesh-colored, telangiectatic, ulcerated nodule → basal cell carcinoma at top of differential
• Standard terminology is essential for:
• Consistency in clinical documentation
• Research
• Communication with other physicians
• Painting analogy for examining skin:
• Step 1 (canvas/forest): Stand back a few feet → overall assessment of general and cutaneous health (skin color, turgor, pallor, jaundice, sun damage, number and location of lesions)
• Step 2 (trees/mountains): Look more closely → describe and categorize specific lesions
• Step 3 (brush strokes): Close examination with magnification → borders of a nevus, blanching with compression
• Analogy: recognizing Georges Seurat by dot-like brush strokes = recognizing melanoma by asymmetry, irregular borders, and multiple colors

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• Dermatology is a visual specialty; some lesions may be diagnosed at a glance
• History is important; in complex cases (e.g., rash and fever, generalized pruritus), history may be crucial
• Dermatologists vary in whether they take history prior to, during, or after physical examination
• In practice, many take a brief history → physical examination → more detailed questioning based on the differential diagnosis suggested by the examination
• Reasons to examine before lengthy history:

1. Certain conditions (e.g., classic plaque-type psoriasis, molluscum contagiosum) have such distinctive morphologies that the diagnosis may be immediately obvious, rendering extensive history taking unnecessary
2. A patient's history may contain "red herrings" leading the physician away from the correct diagnosis; examining first yields a more complete and unbiased differential
3. In certain situations (e.g., evaluation of alopecia), initial examination determines the type of hair loss and allows the physician to pursue a pertinent line of questions

• Primary goal of history taking for a new skin complaint: establish a diagnosis
• Secondary goal: evaluate the patient as a candidate for therapy
• For patients with an established diagnosis: reevaluate the original diagnosis, monitor disease progress and complications, and modify treatment

Chief Complaint and History of the Present Illness

• Duration: When condition was first noted; dates of recurrences or remissions
• Periodicity: Constant, waxing and waning, worst at night, worst in winter
• Evolution: How condition spread or developed over time; useful to ask if lesion "always looked this way" or how it looked when it first started
• Location: Where lesions first noted and how they have spread
• Symptoms: Pruritus, pain, bleeding, nonhealing, change of preexisting moles
• Severity: For painful or pruritic conditions, ask patient to rate on a ten-point scale to follow severity over time
• Ameliorating and Exacerbating Factors: Relation to sun exposure, heat, cold, wind, trauma, exposure to chemicals, topical products, plants, perfumes, metals; relation to menses or pregnancy
• Preceding illness, new medications, new topical products, or exposures
• Therapies tried (including OTC or home remedies) and response to therapy
• Prior similar problems, prior diagnosis, results of biopsies or other studies

Past Medical History

• History of all chronic illnesses, particularly those manifesting in the skin:
• Diabetes, renal and hepatic disease, HIV, hepatitis viruses, polycystic ovarian syndrome, lupus, thyroid disease
• Those associated with skin disease: asthma, allergies
• History of surgical procedures, including organ transplantation and bariatric surgery
• Immunosuppression: Iatrogenic, infectious, genetic
• Pregnancies
• Psychiatric disease
• History of blistering sunburns, exposure to arsenic or ionizing radiation

Medication History

• Detailed history with particular attention to recently started medications
• Categories:
• Prescription
• Over-the-counter medications
• Vitamins and dietary supplements
• Herbal remedies

Allergies

• To medications, foods, environmental antigens, and contactants

Social History

• Occupation, hobbies and leisure activities
• Alcohol and tobacco use, illicit drug use
• Sexual history (including high-risk activities for STDs)
• Dietary history, bathing habits
• Pets, living conditions (alone, with family, homeless, in an institution)
• History of travel or residence in endemic areas for infectious diseases
• Ethnicity, religious practices

Family History

• Of skin disease, atopy (atopic dermatitis, asthma, hay fever), or skin cancer

Review of Systems

• Constitutional symptoms: Fatigue, weight loss, fever, chills, night sweats
• Acute illness symptoms: Headache, photophobia, stiff neck, nausea, vomiting, cough, rhinorrhea, sneezing, myalgias, arthralgias
• Symptoms of associated conditions: Hypothyroidism (cold intolerance, weight gain, constipation); psoriatic arthritis (joint pain, swelling, stiffness)

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• Includes inspection of the entire skin surface, including often-overlooked areas:
• Scalp, eyelids, ears, genitals, buttocks, perineal area, interdigital spaces
• Hair
• Nails
• Mucous membranes of the mouth, eyes, anus, and genitals
• In routine clinical practice, not all areas are examined unless there is a specific reason:
• History of melanoma
• A particular localizing complaint

General Impression of the Patient

• Well or ill
• Obese, cachectic, or normal weight
• Skin Color: Degree of pigmentation, pallor (anemia), carotenemia, jaundice
• Skin Temperature: Warm, cool, clammy
• Skin Surface Characteristics: Xerosis (dryness), seborrhea (excessive oil), turgor, hyper- or hypohidrosis (excessive or decreased sweating), texture
• Degree of Photoaging: Lentigines, actinic purpura, rhytides

Describe the Distribution of Lesions

• Localized (isolated), grouped, regional, generalized, universal, symmetrical
• Sun-exposed, flexural, extensor extremities, acral, intertriginous
• Dermatomal, follicular

Primary Lesions

• Define their type (e.g., papule, plaque, bulla)
• Describe their shape (e.g., arcuate, annular, linear)
• Describe any secondary changes (e.g., crusting, excoriations)

Palpation

• Superficial: Scaly, rough, smooth
• Deep: Firm, rubbery, mobile

Aspects of General Physical Examination That May Be Helpful

• Vital signs
• Abdominal examination for hepatosplenomegaly
• Pulses
• Lymph node examination (especially in cases of suspected infection and malignancy)

• Identification of potentially harmful lesions (e.g., skin cancers) of which the patient is unaware
• Any patient with history of skin cancer or chief complaint of a "new growth" deserves a full skin examination
• Identification of benign lesions (e.g., seborrheic keratoses, angiokeratomas) the patient was concerned about but reluctant to mention → enables physician reassurance
• Finding hidden clues to diagnosis:
• Scabies lesions on the penis
• Psoriatic plaques on the buttocks
• Wickham striae of lichen planus on the buccal mucosa
• Nail pitting in alopecia areata
• Opportunity for patient education (e.g., lentigines are a sign of sun damage → need for improved sun protection)
• Opportunity to convey physician's concern about the patient's skin health as a whole; patients appreciate thoroughness

• Patients may decline when chief complaint is relatively minor or localized (e.g., a wart or acne)
• Patient embarrassment or resistance to disrobing, especially with a physician of opposite gender
• Physician discomfort that patient may misinterpret examination as improper
• Time constraints and lack of personnel to serve as chaperones

• Excellent lighting: Preferably bright, even light that simulates the solar spectrum
• Without good lighting, subtle but important details may be missed
• Patient should be fully undressed, wearing only a gown easily moved aside, with a sheet over the legs if desired
• Underwear, socks, shoes should be removed, as should makeup or eyeglasses
• Examining table at comfortable height, with a head that reclines, extendable footrest, and gynecologic stirrups
• Room at comfortable temperature for the lightly dressed patient
• Sink for hand washing and disinfecting hand foam (patients are reassured by seeing their physician wash hands before examination)
• If patient and physician are of opposite genders, a chaperone makes the examination more comfortable for both

• A magnifying tool (loupe, magnifying glass, and/or dermatoscope)
• A bright focused light (flashlight or penlight) to sidelight lesions
• Glass slides or a hand magnifier for diascopy
• Alcohol pads to remove scale or surface oil
• Gauze pads or tissues with water for removing makeup
• Gloves — used when:
• Scabies or another highly infectious condition (e.g., secondary syphilis) is suspected
• Examining mucous membranes, vulvar and genital areas
• Performing any procedure
• A ruler for measuring lesions
• Number 15 scalpel blade for scraping lesions
• Number 11 scalpel blade for incising lesions
• A camera for photographic documentation
• A Wood's lamp (365 nm) for highlighting subtle pigmentary changes

• No single correct way; each physician has own style
• Common thread: Consistency in order of examining different body areas to ensure no areas are overlooked
• Recommended approach:

1. Observe patient at a distance for general impressions (asymmetry due to stroke, obesity, pallor, fatigue, jaundice)
2. Examine systematically, usually from head to toe, uncovering one area at a time to preserve modesty
3. Move the patient (e.g., sitting to lying) and adjust illumination as needed
4. Palpate growths to determine if soft, fleshy, firm, tender, or fluid-filled
5. Stretch skin with hands — especially useful for basal cell carcinoma (reveals "pearly" quality often not seen on routine inspection)
6. Magnifier on head leaves both hands free for palpation
7. Certain lesions (e.g., porokeratosis) are best examined with side lighting (reveals depth and border details)
8. During examination, name and demystify benign lesions for patient reassurance

• Special techniques for hair disorders (see Chapter 88):
• Patient sits in a chair so entire scalp is easily examined
• Part the hair at the front and occiput
• Gently tug on hairs to determine fraction of loose (telogen) hairs
• Nail examination: See Chapter 89
• After examination:
• Document skin findings (type of lesions and locations) descriptively or on a body map
• Careful documentation is particularly important for suspicious lesions to be biopsied → exact location found and treated later
• Instant or digital photography is a useful adjunct

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• Siemens (1891–1969): "He who studies skin diseases and fails to study the lesion first will never learn dermatology."
• The primary skin lesion (or its evolution) is the essential element on which clinical diagnosis rests
• Joseph Jakob von Plenck (1738–1807) and Robert Willan (1757–1812): Defined basic morphologic terminology; laid the foundation for description and comparison of fundamental lesions
• Wolff and Johnson analogy: To read words, one must recognize letters; to read the skin, one must recognize the basic lesions. To understand a paragraph, one must know how words are put together; to arrive at a differential diagnosis, one must know what the basic lesions represent, how they evolve, and how they are arranged and distributed
• Dermatology Lexicon Project: Mission to create a universally accepted and comprehensive glossary of descriptive terms to support research, medical informatics, and patient care
• Variation and ambiguity in morphologic terms have created barriers to communication among physicians
• Example: The papule has been variously described as no greater than 1 cm, less than 0.5 cm, or ranging from the size of a pinhead to that of a split pea

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• A solid, elevated lesion less than 0.5 cm in size
• A significant portion projects above the plane of the surrounding skin
• Papules surmounted with scale → papulosquamous lesions
• Common shapes and surfaces: sessile, pedunculated, dome-shaped, flat-topped, rough, smooth, filiform, mammillated, acuminate, umbilicated
• Clinical example: Lichen planus (Chapter 26)
• Multiple, well-defined papules of varying sizes with flat tops and glistening surface

• A solid plateau-like elevation occupying a relatively large surface area compared to its height above normal skin
• Diameter larger than 0.5 cm
• Further characterized by size, shape, color, and surface change
• Clinical example: Psoriasis (Chapter 18)
• Well-demarcated pink plaques with silvery scale

• A solid, round or ellipsoidal, palpable lesion with diameter larger than 0.5 cm
• Size is not the major consideration in defining a nodule
• Depth of involvement and/or substantive palpability (rather than diameter) differentiate a nodule from a large papule or plaque
• Five main types based on anatomic component(s) involved:

1. Epidermal
2. Epidermal–dermal
3. Dermal
4. Dermal–subdermal
5. Subcutaneous

• Additional diagnostic features: warm, hard, soft, fluctuant, movable, fixed, painful
• Different surfaces: smooth, keratotic, ulcerated, fungating
• Clinical example: Nodular basal cell carcinoma (Chapter 115)
• Well-defined, firm nodule with glistening surface through which telangiectasia can be seen
• Tumor: General term for any mass, benign or malignant (sometimes included under the heading of nodule)
• Gumma: Specifically the granulomatous nodular lesion of tertiary syphilis

• An encapsulated cavity or sac lined with a true epithelium containing fluid or semisolid material (cells and cell products such as keratin)
• Spherical or oval shape results from tendency of contents to spread equally in all directions
• Depending on contents: hard, doughy, or fluctuant
• Clinical example: Cystic hidradenoma (Chapter 119)
• Bluish colored resilient cyst filled with mucous-like material on the cheek

• A swelling of the skin that is characteristically evanescent, disappearing within hours
• Also known as hives or urticaria
• Result of edema produced by escape of plasma through vessel walls in the upper portion of the dermis
• May be tiny papules or giant plaques
• May take various shapes: round, oval, serpiginous, or annular (often in the same patient)
• Borders: Sharp but not stable — move from involved to adjacent uninvolved areas over hours
• Flare (ring of pink erythema): May be intense if superficial vessels are dilated
• If edema is sufficient to compress superficial vessels → wheals may be white in the center or around the periphery (zone of pallor)
• With associated inflammatory disruption of vessel walls → deeper red color, may be purpuric, and are more persistent
• Clinical example: Dermatographism (Chapter 38)
• Sharply demarcated wheal with surrounding erythematous flare occurring within seconds of skin being stroked
• Angioedema: A deeper edematous reaction occurring in areas with very loose dermis and subcutaneous tissue:
• Lip, eyelid, scrotum
• May occur on hands and feet
• Can result in grotesque deformity

• Arises from proliferation of fibrous tissue replacing previously normal collagen after a wound or ulceration breaches the reticular dermis
• Color evolution: Deeper pink to red early on → hypo- or hyperpigmented later
• In most scars: epidermis is thinned and imparts a wrinkled appearance at the surface
• Adnexal structures (e.g., hair follicles) normally present in the dermis are absent
• Hypertrophic scars: Firm papules, plaques, or nodules (see Chapter 66)
• Keloid scars: Also elevated; unlike hypertrophic scars, keloids exceed the area of initial wounding with web-like extensions
• Atrophic scars: Thin depressed plaques

• A hair follicle infundibulum dilated and plugged by keratin and lipids
• Open comedo:
• Pilosebaceous unit open to the skin surface with visible keratinaceous plug
• Black color due to oxidized sebaceous content of the infundibulum ("blackhead")
• Closed comedo:
• Closed infundibulum with unapparent follicular opening
• Accumulates whitish keratin
• Clinical example: Comedonal acne (Chapter 80)

• A hyperkeratotic conical mass of cornified cells arising over an abnormally differentiating epidermis
• Clinical example: Verruca vulgaris (Chapter 196)

• Deposits of calcium in the dermis or subcutaneous tissue
• Appreciated as hard, whitish nodules or plaques, with or without visible alteration of the skin's surface
• Clinical example: Cutaneous calcinosis in dermatomyositis (Chapter 156)

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• A moist, circumscribed, depressed lesion resulting from loss of a portion or all of the viable epidermal or mucosal epithelium
• Defect extending to the most superficial part of the dermis → pinpoint bleeding in a sieve-like fashion
• Causes: Trauma, detachment of epidermal layers with maceration, rupture of vesicles or bullae, epidermal necrosis
• Unless secondarily infected, erosions do not scar
• Clinical example: Toxic epidermal necrolysis (Chapter 40)
• Sloughing of the skin leaves behind a large erosion

• A defect in which the epidermis and at least the upper (papillary) dermis have been destroyed
• Breach of the dermis and destruction of adnexal structures impede reepithelialization → heals with scarring
• Borders: Rolled, undermined, punched out, jagged, or angular
• Base: Clean, ragged, or necrotic
• Discharge: Purulent, granular, or malodorous
• Surrounding skin: Red, purple, pigmented, reticulated, indurated, sclerotic, or infarcted
• Clinical example: Pyoderma gangrenosum (Chapter 33)
• Large ulcer with ragged base and heaped-up pink erythematous border on the leg

• Refers to a diminution in the size of a cell, tissue, organ, or part of the body
• Atrophic epidermis: Glossy, almost transparent, paper thin and wrinkled; may not retain normal skin lines
• Atrophy of the papillary or reticular dermal connective tissue: Manifests as a depression of the skin
• Atrophy of the panniculus: Results in a more substantial depression of the skin
• Example: Aged skin of the arm in an elderly woman (Chapter 109)

• As a morphologic term, refers to the combination of:
• Atrophy
• Telangiectasia
• Varied pigmentary changes (hyper- and hypo-)
• These features may give a dappled appearance to the skin
• Clinical example: Chronic radiodermatitis

• A tract connecting deep suppurative cavities to each other or to the surface of the skin
• Clinical example: Hidradenitis suppurativa (Chapter 85)

• Linear depressions of the skin, usually measuring several centimeters in length
• Result from changes to the reticular collagen that occur with rapid stretching of the skin
• Clinical example: Striae distensae (Chapter 108)

• A wavy, threadlike tunnel through the outer portion of the epidermis excavated by a parasite
• Clinical example: Scabetic burrow (Chapter 208)

• A circumscribed or diffuse hardening or induration of the skin resulting from dermal fibrosis
• Detected more easily by palpation: skin may feel board-like, immobile, and difficult to pick up
• Clinical example: Morphea (Chapter 64)

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• Flat, even with the surface level of surrounding skin
• Perceptible only as an area of color different from the surrounding skin or mucous membrane
• Maculosquamous: Neologism for macules with fine nonpalpable scaling, which may become apparent only after light scraping and scratching
• Color — perhaps the most important additional feature of a lesion other than primary morphology:
• First visual assessment made
• Reliably reproducible with particular pathologies (e.g., destruction of melanocytes, dilatation of dermal blood vessels, inflammation of vessel walls with extravasation of RBCs)
• Provides meaningful insight into pathologic processes and facilitates clinical diagnosis
• Pigmentary changes — an important and common type of macular color change:
• Hyperpigmented (e.g., postinflammatory hyperpigmentation)
• Hypopigmented (e.g., tinea versicolor)
• Depigmented (e.g., vitiligo)
• Clinical example: Lentigo (Chapter 122)
• Uniform-colored brown macule with slightly irregular, sharply defined borders on the lip

• Similar to a macule; a flat area of skin or mucous membrane with a different color from its surrounding
• Larger than 0.5 cm; may have a fine, very thin scale
• Clinical examples:
• Vitiligo (Chapter 74): "Patch" describes larger macules or a "patchy" configuration; depigmented patches within areas of normal skin tone
• Cutaneous T-cell lymphoma: Early lesions may be thin slightly scaly patches

• The blanchable pink to red color of skin or mucous membrane due to dilatation of arteries and veins in the papillary and reticular dermis
• Exists in different colors; calling a primary lesion "erythematous" alone is incomplete
• Describing erythema with the color it most closely resembles provides a meaningful clue to diagnosis:
• Violaceous erythema → distinct differential from salmon pink-colored erythema, even if both involve papules
• Clinical example: Dusky erythema as in fixed drug eruption (Chapter 41)

• Generalized deep redness of the skin involving more than 90% of the body surface within days to weeks
• Type of scaling or desquamation that follows establishment of generalized erythema is suggestive of the primary process
• Clinical example: Sézary syndrome (Chapters 23 and 145)

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• A scale is a flat plate or flake arising from the outermost layer of the stratum corneum
• Groups of coherent cornified cells packed with filamentous proteins desquamate imperceptibly under normal circumstances on a regular basis
• The epidermis is replaced completely every 27 days
• When epidermal differentiation is disordered → accumulation and casting of stratum corneum becomes apparent as scale
• Scale ranges from fine dust-like particles to extensive parchment-like sheets
• Latent desquamation: Scale observed only after scratching the lesion
• Scaly lesions are often described as "hyperkeratotic" — used both clinically and histopathologically
• Not all scales are similar — close examination of the type of scale provides diagnostically useful information
• Clinical example: Psoriasis vulgaris (Chapter 18)
• Brittle silvery scales forming thin platelets in several loose sheets, like mica

• Leider and Rosenblum define hyperkeratosis as "excessive cornification"
• Siemens states the stratum corneum may be thinned or thickened
• Thickening may consist of normal keratin (hyperkeratosis) or abnormal keratin in which the cellular nuclei are retained and stainable (parakeratosis)
• Different types discernible histopathologically
• In clinical parlance: "hyperkeratosis" refers to an excessive or thickened stratum corneum, often but not always scaly

• Hardened deposits resulting when serum, blood, or purulent exudate dries on the surface of the skin
• Color by type of secretion:
• Yellow-brown: Dried serous secretion
• Turbid yellowish-green: Purulent secretion
• Reddish-black: Hemorrhagic secretion
• Removal of the crust may reveal an underlying erosion or ulcer
• Clinical example: Impetigo (Chapter 176)
• Glistening, honey-colored, delicate crusts under the nose

• Surface excavations of epidermis that result from scratching

• A linear loss of continuity of the skin's surface or mucosa resulting from excessive tension or decreased elasticity of the involved tissue
• Frequently occur on the palms and soles where the thick stratum corneum is least expandable
• Clinical example: Fissure on the palm associated with contact dermatitis (Chapter 13)

• Repeated rubbing of the skin induces a reactive thickening of the epidermis with changes in the collagen of the underlying superficial dermis
• Produces thickened skin with accentuated markings (may resemble tree bark)
• Clinical example: Lichen simplex chronicus (Chapter 15)
• Area of thickened skin with accentuated skin markings induced by repeated rubbing

• An excessive accumulation of scale (hyperkeratosis) resulting in a yellowish thickening of the skin, usually on the palms or soles
• May be:
• Inherited (abnormal keratin formation)
• Acquired (mechanical stimulation)
• Clinical example: Plantar keratoderma in psoriasis (Chapter 18)

• Implies tissue necrosis, infarction, deep burns, gangrene, or other ulcerating process
• A circumscribed, adherent, hard, black crust on the surface of the skin
• Initially moist, protein rich, and avascular
• Clinical example: Thermal burn (Chapter 95)

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• Vesicle: Fluid-filled cavity or elevation smaller than or equal to 0.5 cm
• Bulla (blister): Measures larger than 0.5 cm
• Fluid in the cavity exerts equal pressure in all directions → spherical shape
• Because of their size, bullae are easily identifiable as tense or flaccid weepy blisters
• Contents may be: clear, serous, hemorrhagic, or pus-filled (when cavity wall is thin and translucent enough)
• Arise from cleavage at various levels:
• Intraepidermal (within the epidermis)
• Subepidermal (at the dermal–epidermal interface)
• Amount of pressure required to collapse the lesion may help predict intraepidermal vs. subepidermal, but reliable differentiation requires histopathologic examination of the blister cavity edge
• Clinical example of vesicle: Impetigo caused by toxin-producing staphylococci (Chapter 177)
• Fragile subcorneal translucent vesicles
• Clinical example of bulla: Bullous pemphigoid (Chapter 56)
• Large tense subepidermal bullae filled with serous or hemorrhagic fluid

• A circumscribed, raised cavity in the epidermis or infundibulum containing pus
• Purulent exudate composed of leukocytes with or without cellular debris
• May contain bacteria or may be sterile
• Color depends on sterility: white, yellow, or greenish-yellow
• May vary in size and may coalesce to form "lakes" of pus
• When associated with hair follicles → may appear conical and contain a hair in the center
• Clinical example: Superficial pyoderma (Chapter 176)

• A deep necrotizing folliculitis with suppuration (Chapter 176)
• Presents as an inflamed follicle-centered nodule usually greater than 1 cm with:
• A central necrotic plug
• An overlying pustule
• Several furuncles may coalesce to form a carbuncle

• A localized accumulation of purulent material so deep in the dermis or subcutaneous tissue that pus is usually not visible on the skin surface (Chapter 176)
• A pink erythematous, warm, tender, fluctuant nodule

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• Extravasation of red blood from cutaneous vessels into skin or mucous membranes → reddish-purple lesions
• Diascopy — application of pressure with two glass slides or an unbreakable clear lens:
• Simple and reliable method for differentiating erythema (vascular dilatation) from purpura (extravasated erythrocytes or erythrocyte products)
• If redness is nonblanching under pressure → the lesion is purpuric
• As extravasated RBCs decompose over time → color changes from bluish-red to yellowish-brown or green
• Petechiae: Small, pinpoint purpuric macules
• Ecchymoses: Larger, bruise-like purpuric patches
• Petechiae and ecchymoses correspond to a noninflammatory extravasation of blood
• Palpable purpura: If a lesion is purpuric and palpable → suggests an inflammatory insult to the vessel wall as a cause of extravasation of blood and inflammatory cells
• Clinical example: Leukocytoclastic vasculitis (Chapter 163)
• Nonblanching red erythematous papules and plaques (palpable purpura) on the legs

• Persistent dilatations of small capillaries in the superficial dermis (Chapter 174)
• Visible as fine, bright, nonpulsatile red lines or net-like patterns on the skin

• An area of cutaneous necrosis resulting from a bland or inflammatory occlusion of blood vessels in the skin
• Presents as a tender, irregularly shaped dusky reddish-gray macule or firm plaque
• Sometimes depressed slightly below the plane of the skin
• Clinical example: Cholesterol emboli (Chapter 173)
• Dusky purple discoloration representing infarction that eventuates in tissue necrosis; cholesterol emboli lodged in distal end arteries of the toes

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• Once lesion type(s) are identified → describe shape, arrangement, and pattern of distribution
• All useful characteristics in morphologic diagnosis
• Example: A single scaly plaque on the trunk → broad differential; but the same plaques symmetrically distributed on the elbows, knees, and umbilicus → highly suggestive of psoriasis
• Shape and arrangement descriptions may apply to single or multiple lesions

• Annular: Ring-shaped
• Edge of the lesion differs from the center (raised, scaly, or differing in color)
• Examples: Granuloma annulare, tinea corporis, erythema annulare centrifugum
• Round/nummular/discoid: Coin-shaped
• Usually a round to oval lesion with uniform morphology from edges to center
• Examples: Nummular eczema, plaque-type psoriasis, discoid lupus
• Polycyclic: Formed from coalescing circles, rings, or incomplete rings
• Examples: Urticaria, subacute cutaneous lupus erythematosus
• Arcuate: Arc-shaped
• Often a result of incomplete formation of an annular lesion
• Examples: Urticaria, subacute cutaneous lupus erythematosus
• Linear: Resembling a straight line
• Often implies an external contactant or Koebner phenomenon in response to scratching
• May apply to a single lesion (e.g., scabies burrow, poison ivy dermatitis, bleomycin pigmentation) or arrangement of multiple lesions (e.g., lichen nitidus, lichen planus)
• Reticular: Net-like or lacy
• Somewhat regularly spaced rings or partial rings with sparing of intervening skin
• Examples: Livedo reticularis, cutis marmorata
• Serpiginous: Serpentine or snake-like
• Example: Cutaneous larva migrans (larva migrates through the skin in a wandering pattern)
• Targetoid: Target-like, with at least three distinct zones
• Example: Erythema multiforme
• Whorled: Like marble cake
• Two distinct colors interspersed in a wavy pattern
• Usually seen in mosaic disorders in which cells of differing genotypes are interspersed
• Examples: Incontinentia pigmenti, hypomelanosis of Ito, linear and whorled nevoid hypermelanosis

• Grouped/herpetiform: Lesions clustered together
• Classic example: Herpes simplex virus 1 reactivation as grouped vesicles on an erythematous base
• Also seen with certain arthropod bites
• Scattered: Irregularly distributed

• Dermatomal/zosteriform: Unilateral and lying in the distribution of a single spinal afferent nerve root
• Classic example: Herpes zoster (Chapter 194)
• Blaschkoid: Following lines of skin cell migration during embryogenesis
• Generally longitudinally oriented on the limbs and circumferential on the trunk, but not perfectly linear
• Described by Alfred Blaschko → implies a mosaic disorder
• Examples: Incontinentia pigmenti, inflammatory linear verrucous epidermal nevus
• Lymphangitic: Lying along the distribution of a lymph vessel
• Implies an infectious agent spreading centrally from an acral site
• Usually a red streak along a limb due to a staphylococcal or streptococcal cellulitis
• Sun exposed: Areas usually not covered by clothing
• Face, dorsal hands, and a triangular area corresponding to the opening of a V-neck shirt on the upper chest
• Examples: Photodermatitis, subacute cutaneous lupus erythematosus, polymorphous light eruption, squamous cell carcinoma
• Sun protected: Areas usually covered by one or more layers of clothing
• Usually a dermatosis improved by sun exposure
• Examples: Parapsoriasis, mycosis fungoides
• Acral: Distal locations — hands, feet, wrists, ankles
• Examples: Palmoplantar pustulosis, chilblains
• Truncal: Occurring on the trunk or central body
• Extensor: Over dorsal extremities, overlying extensor muscles, knees, or elbows
• Example: Psoriasis
• Flexor: Overlying flexor muscles of the extremities, the antecubital and popliteal fossae
• Example: Atopic dermatitis
• Intertriginous: Occurring in the skin folds where two skin surfaces are in contact
• Axillae, inguinal folds, inner thighs, inframammary skin, under an abdominal pannus
• Often related to moisture and heat
• Example: Candidiasis
• Localized: Confined to a single body location
• Example: Cellulitis
• Generalized: Widespread
• A generalized eruption of inflammatory (red) lesions = an exanthema (rash)
• Macular exanthema (macules), papular exanthema (papules), vesicular exanthema (vesicles), etc.
• Examples: Viral exanthems, drug eruption
• Bilateral symmetric: Mirror-image symmetry on both sides of the body
• Examples: Vitiligo, plaque-type psoriasis
• Universal: Involving the entire cutaneous surface
• Examples: Erythroderma, alopecia universalis

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1. Approach each and every evaluation with patience and thoroughness
2. Beware of "snap," "curbside," or "doorway" diagnoses
3. Examine the entire mucocutaneous surface, as well as the hair and nails
4. A new or changing mole should be carefully evaluated
5. Do not remove tissue without sending a portion for histologic examination
6. If the dermatopathologic findings are not consistent with the clinical impression, obtain another biopsy
7. If forced to choose between incongruent clinical and pathologic impression, follow clinical lead (cautiously)
8. Generalized pruritus of more than 1 month's duration mandates a complete systemic workup
9. Seemingly nonspecific rashes may just be camouflaged specific disorders
10. Drug-induced eruptions can mimic most skin conditions
11. Be wary of the "atypical" diagnosis. Atypical "this" may be "typical" that to someone who has seen it before
12. Consider all other reasonable possibilities before making a diagnosis of factitial disorder

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• Thomas B. Fitzpatrick: "Dermatologists are physicians who can diagnose a rash!"
• Dermatologists may also be internists, surgeons, biochemists, or immunologists
• Without competency in dermatologic diagnosis, one cannot qualify as a dermatologist
• Any physician who makes the effort to study the skin and learn the dermatologic lexicon can develop a functional appreciation of the fundamentals
• The advanced diagnostic eye can only be acquired by endlessly repeated encounters with an experienced mentor
• Most common error in dermatologic diagnosis: Regarding lesions as nonspecific "rashes" rather than as aggregates of specific individual lesions
• Like surveying a blood smear — a "general impression" is not enough; morphologic aspects of each individual cell must be carefully scrutinized
• Lewis Thomas: "Medicine is no longer the laying on of hands, it is more like the reading of signals from machines."
• In dermatology, there can be no replacement for the laying on of hands; the physician reads signals from people, not machines

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• In some patients the appearance of skin lesions is so distinctive that the diagnosis is clear at a glance.
• In others, subjective symptoms and clinical signs alone are inadequate — a complete history and laboratory examination, including a biopsy, are essential.
• The same disease may show variations under different conditions and in different individuals.
• Lesion appearance may be modified by previous treatment or obscured by extraneous influences such as scratching or secondary infection.
• Underlying erythema may be difficult to discern in patients with darker skin tones.
• Subjective symptoms may be the ONLY evidence of disease, as in pruritus, with a generally unremarkable skin appearance.
• Although history is important, dermatologic diagnosis is most frequently made on OBJECTIVE physical characteristics and the location/distribution of one or more lesions that can be seen or felt.
• Therefore careful physical examination of the skin is paramount.

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• Most skin diseases present with lesions that have distinct characteristics; they may be uniform or diverse in size, shape, and color, or in different stages of evolution or involution.
• Primary lesions = the original lesions; identifying them is the MOST important aspect of the dermatologic physical examination.
• Primary lesions may continue to full development or be modified by regression, trauma, or other extraneous factors, producing secondary lesions.

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• The forms are: macules (or patches), papules (or plaques), nodules, tumors, wheals, vesicles, bullae, and pustules.

• Variously sized, circumscribed changes in skin color, WITHOUT elevation or depression (NONpalpable) (macular depigmentation, vitiligo).
• May be circular, oval, or irregular.
• May be distinct in outline or may fade into the surrounding skin.
• May constitute the whole lesion, part of the eruption, or merely an early phase.
• If lesions become slightly raised, they are then designated papules or, in some cases, morbilliform eruptions.

• A large macule, 1 cm or greater in diameter.
• Examples: nevus flammeus, vitiligo.

• Circumscribed, solid elevations with NO visible fluid, varying in size from a pinhead to 1 cm (sarcoidosis).
• Shapes: acuminate, rounded, conical, flat topped, or umbilicated.
• Colors: white (milium), red (eczema), yellowish (xanthoma), black (melanoma).
• Generally centered in the dermis; may be concentrated at the orifices of the sweat ducts or at the hair follicles.
• May be of soft or firm consistency; surface may be smooth or rough.
• If capped by scales, the eruption is called papulosquamous.
• Distribution: some are discrete and irregularly distributed (papular urticaria); others are grouped (lichen nitidus).
• Some persist as papules; those of the inflammatory type may progress to vesicles or pustules, or may erode before regression.
• TERMINOLOGY: the term "maculopapular" should NOT be used — there is no such thing as a "maculopapule", although there may be both macules and papules in an eruption. Typically such eruptions are morbilliform.

• A broad papule (or confluence of papules), 1 cm or more in diameter (hyperkeratotic plaques of psoriasis).
• Generally flat but may be centrally depressed.

• Morphologically like papules but LARGER than 1 cm in diameter.
• Most frequently centered in the dermis or subcutaneous fat.

• Soft or firm, freely movable or fixed masses of various sizes and shapes, usually greater than 2 cm in diameter (papules, nodules, and tumors of neurofibromatosis).
• General usage dictates that the word "tumor" means a NEOPLASM.
• May be elevated or deep seated, and in some cases pedunculated (neurofibromas).
• Tend to be rounded; consistency depends on the constituents of the lesion.
• Some remain stationary indefinitely; others increase in size or break down.

• Evanescent, edematous, plateau-like elevations of various sizes (acute urticaria).
• Usually oval or of arcuate contours, pink to red, surrounded by a "flare" of macular erythema.
• May be discrete or may coalesce.
• Often develop quickly (minutes to hours).
• The wheal is the prototypic lesion of urticaria; diseases in which wheals are prominent are described as "urticarial" (e.g., urticarial vasculitis).
• Dermatographism = pressure-induced whealing, may be evident.

• Circumscribed, fluid-containing elevations 1–10 mm in size (herpes zoster in an HIV-infected patient).
• May be clear from serous exudate or red from serum mixed with blood.
• Apex may be rounded, acuminate, or umbilicated — as in eczema herpeticum.
• Arrangement: discrete, irregularly scattered, grouped (e.g., herpes zoster), or linear (allergic contact dermatitis from urushiol — poison ivy/oak).
• May arise directly or from a macule or papule, and generally lose their identity in a short time.
• May break spontaneously or develop into bullae through coalescence or enlargement.
• The inflammatory process may lead to pustule formation; when contents are seropurulent, lesions are known as vesicopustules.
• Compartments: unilocular (single cavity) or multilocular (several compartments).

• Rounded or irregularly shaped blisters containing serous or serosanguineous fluid.
• Differ from vesicles ONLY in size — larger than 1 cm.
• Usually unilocular but may be multilocular.
• Superficial (in the epidermis): walls are flaccid and thin, subject to rupture spontaneously or from slight injury.
• After rupture, remnants of thin walls may persist and, with exudate, may dry to form a thin crust.
• Alternatively, the broken bleb may leave a raw and moist base, which may be covered with seropurulent or purulent exudate.
• Less frequently, irregular vegetations may appear on the base (as in pemphigus vegetans).
• Subepidermal bullae: tense, do NOT rupture easily, and are often present when the patient is examined.

Bullous Diagnostic Signs

• Nikolsky sign — putting lateral pressure on UNBLISTERED skin in a patient with a bullous eruption; positive when the epithelium shears off.
• Asboe-Hansen sign — extension of a blister to adjacent, unblistered skin when pressure is put on the top of the blister.
• Both signs demonstrate the principle that in some diseases the extent of microscopic vesiculation is MORE than what is evident by simple inspection.
• Useful in evaluating the severity of pemphigus vulgaris and severe bullous drug reactions.
• Hemorrhagic bullae are common in: pemphigus, herpes zoster, severe bullous drug reactions, and lichen sclerosus.
• Cellular contents of bullae may be useful in cytologically confirming the diagnosis of pemphigus, herpes zoster, and herpes simplex.

• Small elevations of the skin containing purulent material, usually necrotic inflammatory cells (eosinophilic pustular folliculitis, Ofuji disease).
• Like vesicles in shape and usually have an inflammatory areola.
• Usually white or yellow centrally, but have a red tinge if they also contain blood.
• May originate as pustules or develop from papules or vesicles.

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• Of many types; the most important are: scales, crusts, erosions, ulcers, fissures, and scars.

• Dry or greasy laminated masses of keratin.
• The body ordinarily constantly sheds imperceptible tiny, thin fragments of stratum corneum.
• When formation of epidermal cells is rapid or the process of normal keratinization is disturbed, pathologic exfoliation results, producing scales.
• Size variation:
• Fine, delicate, and branny — tinea versicolor.
• Coarser — eczema and ichthyosis.
• Stratified — psoriasis.
• Color: vary from white-gray to yellow or brown from admixture of dirt or melanin.
• Micaceous scales: occasionally a silvery sheen from trapping of air between their layers — characteristic of psoriasis.
• When scaling occurs, it usually suggests a pathologic process in the epidermis, and parakeratosis is often present histologically.

• Dried serum, pus, or blood, usually mixed with epithelial and sometimes bacterial debris.
• When crusts become detached, the base may be dry or red and moist.

• Excoriation — a punctate or linear abrasion produced by mechanical means, usually involving only the epidermis but sometimes reaching the papillary layer of the dermis.
• Caused by scratching with the fingernails in an effort to relieve itching.
• Abrasion — the term used if the skin damage is the result of mechanical trauma or constant friction.
• Frequently there is an inflammatory areola around the excoriation, or a covering of yellowish dried serum or red dried blood.
• Complications: excoriations may provide access for pyogenic microorganisms → formation of crusts, pustules, or cellulitis, occasionally associated with enlargement of the neighboring lymphatic glands.

• A linear cleft through the epidermis or into the dermis.
• May be single or multiple; vary from microscopic to several centimeters in length, with sharply defined margins.
• May be dry or moist, red, straight, curved, irregular, or branching.
• Occur most often when the skin is thickened and inelastic from inflammation and dryness, especially in regions subjected to frequent movement.
• Typical sites: tips and flexural creases of the thumbs, fingers, and palms; edges of the heels; clefts between the fingers and toes; angles of the mouth; the lips; around the nares, auricles, and anus.
• Chapping — when skin is dry, exposure to cold, wind, water, and cleaning products (soap, detergents) may produce a stinging, burning sensation, indicating microscopic fissuring is present (as in "chapped lips").
• When fissuring is present, pain is often produced by movement of the parts, which opens or deepens the fissures or forms new ones.

• Loss of all or portions of the EPIDERMIS ALONE, as in impetigo.
• May or may not become crusted, but HEALS WITHOUT A SCAR.

• Rounded or irregularly shaped excavations resulting from complete loss of the epidermis PLUS some portion of the dermis (ulcer of the lip, chancre of primary syphilis).
• Vary in diameter from a few millimeters to several centimeters.
• Shallow — involving little beyond the epidermis, as in dystrophic epidermolysis bullosa, the base formed by the papillary layer.
• Deep — extending into the dermis, subcutaneous tissues, or deeper, as with leg ulcers.
• ULCERS HEAL WITH SCARRING.

• Composed of new connective tissue that has replaced lost substance in the dermis or deeper parts resulting from injury or disease, as part of the normal reparative process.
• Size and shape are determined by the form of the previous destruction.
• Scarring is characteristic of certain inflammatory processes and is therefore of diagnostic value; the pattern of scarring may be characteristic of a particular disease.
• Key contrast: lichen planus and discoid lupus erythematosus have inflammation in relatively the same anatomic area, yet:
• Discoid lupus CHARACTERISTICALLY causes scarring as it resolves.
• Lichen planus RARELY results in scarring of the skin.
• BOTH processes, however, cause scarring of the HAIR FOLLICLES when occurring on the scalp.
• Scars may be thin and atrophic, or fibrous elements may develop into neoplastic overgrowths — hypertrophic scars or keloids.
• Some individuals and some body areas — especially the anterior chest and upper back — are especially prone to hypertrophic scarring.
• Color evolution: scars first tend to be pink or violaceous, later becoming white and glistening in White patients.
• In Black patients, keloid scars are often DARKER than the surrounding skin.
• Scars are persistent but usually become softer, less elevated, and less noticeable over years.

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• Interpretation of the clinical picture may be difficult because identical clinical lesions may have many different causes.
• Moreover, the same skin disease may give rise to diverse eruptions.
• Thus for each specific type of primary morphologic lesion there is a differential diagnosis of conditions producing that lesion; and there is a parallel list of all the variations a single skin disease can cause.
• Being superficial, skin lesions can be easily observed and palpated.
• Magnification with a hand lens, dermatoscope, or other imaging devices may be easily applied, enhancing visualization of fine details and even histologic findings.
• Smears and cultures may be readily obtained for infectious organisms.
• Biopsy and histologic examination make histopathology an important component of many dermatologic evaluations.
• THE THRESHOLD FOR BIOPSY SHOULD BE LOW — especially true of:
• Inflammatory dermatoses
• Potentially infectious conditions
• Skin disorders in immunosuppressed and hospitalized patients, in whom clinical morphology may be atypical
• Once therapy is begun empirically, histologic features may be ALTERED by the treatment, making pathologic diagnosis more difficult.

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• Important elements: age, health, occupation, ethnic background, hobbies, diet, recent travel, and living conditions.
• Also: onset, duration, and course of the disease, and the response to previous treatment.
• Family history of similar disorders and other related diseases may be useful.
• A COMPLETE DRUG HISTORY IS ONE OF THE MOST IMPORTANT ASPECTS of a thorough history. This includes:
• Prescription and over-the-counter medications
• Supplements
• Herbal products
• Vaccinations
• Eyedrops
• Suppositories
• Drug reactions are frequent and may simulate many different skin diseases both clinically and histologically.
• Equally important: inquire about topical agents applied or affixed to the skin and mucous membranes for medicinal or cosmetic purposes, because these may cause cutaneous OR SYSTEMIC reactions.
• A complete medical history including other medical diagnoses is essential — certain skin diseases are specific to or associated with other conditions, e.g., cutaneous Crohn's disease and pyoderma gangrenosum in Crohn's disease.
• Also important: travel abroad, the patient's environment at home and at work, seasonal occurrences and recurrences, and the temperature, humidity, and weather exposure of the patient — especially if homeless.
• Habitation in certain parts of the world predisposes to distinctive diseases for that geographic locale, including:
• San Joaquin Valley fever (coccidioidomycosis)
• Hansen disease
• Leishmaniasis
• Histoplasmosis
• Sexual practices may be relevant, as in genital ulcer diseases and human immunodeficiency virus (HIV) infection.

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• Should be conducted in a well-lit room; natural sunlight is the ideal illumination.
• Abnormalities of melanin pigmentation (e.g., vitiligo, melasma) are more clearly visible under ultraviolet (UV) light.
• A Wood's light (365 nm) is most often used, and is also valuable for diagnosis of:
• Some types of tinea capitis
• Tinea versicolor
• Erythrasma
• A magnifying lens and dermatoscope are of inestimable value in examining small lesions.
• Palpate the lesion for firmness and fluctuation; rubbing will elucidate the nature of scales; scraping will reveal the nature of the lesion's base.
• Pigmented lesions, especially in infants, should be RUBBED to elicit DARIER SIGN (whealing), as seen in urticaria pigmentosa.
• Dermoscopy is an especially important part of the examination of NEOPLASMS.
• The ENTIRE eruption must be seen to evaluate distribution and configuration.
• Optimally done by having the patient COMPLETELY UNDRESS and viewing from a distance to take in the whole eruption at once.
• "Peek-a-boo" examination — exposing one anatomic area after another while remaining clothed — is NOT optimal: the examination will be incomplete and the overall distribution difficult to determine.
• After the patient is viewed at a distance, individual lesions are examined to identify primary lesions and to determine the evolution of the eruption and the presence of secondary lesions.

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• Lesions may be few or numerous; in arrangement they may be discrete or may coalesce to form patches of peculiar configuration.
• Lesions may appear over the entire body or may follow:
• Lines of cleavage — pityriasis rosea
• Dermatomes — herpes zoster
• Lines of Blaschko — epidermal nevi (linear epidermal nevus, blaschkoid)
• Lesions may form groups, rings, crescents, or unusual linear patterns.
• A remarkable degree of BILATERAL SYMMETRY is characteristic of certain diseases: dermatitis herpetiformis, vitiligo, and psoriasis.

• Some lesions appear fully evolved.
• Others develop from smaller lesions, then remain the same during their entire existence (e.g., warts).
• When lesions succeed one another in a series of CROPS — as in varicella and dermatitis herpetiformis — a POLYMORPHOUS eruption results, with lesions in various stages of development or involution all present at the same time.

• Certain lesions disappear completely, whereas others leave characteristic residual pigmentation or scarring.
• Residual dyspigmentation, although a significant cosmetic issue, is NOT considered a scar.
• The pattern in which lesions involute may be useful in diagnosis, as with the typical keratotic papule of pityriasis lichenoides et varioliformis acuta (PLEVA).

• Grouping is characteristic of: dermatitis herpetiformis, herpes simplex, and herpes zoster.
• Corymbose (corymbiform) — small lesions arranged around a large one.
• Concentric annular lesions are typical of borderline Hansen disease and erythema multiforme; sometimes said to be in a "COCKADE" pattern, referring to the tricolor cockade hats worn by French revolutionists.
• Flea and other arthropod bites are usually grouped and linear — the "breakfast-lunch-and-dinner" sign.
• Agminated — grouped lesions of various sizes.

• Terms describing the configuration an eruption assumes either primarily or by enlargement or coalescence:
• Linear — lesions in a line; may be confluent or discrete.
• Annular — a complete circle with normal-appearing skin centrally (borderline leprosy).
• Arcuate or gyrate — a portion of a circle.
• Polycyclic — composed of several intersecting portions of circles.
• Serpiginous — not straight but does not form parts of circles (cutaneous larva migrans).
• Guttate — round lesions that are small, like drops.
• Nummular — round lesions that are larger, like a coin.
• Unusual configurations that do NOT correspond to these patterns or to normal anatomic or embryonic patterns should raise the possibility of an EXOGENOUS dermatosis or FACTITIA.

• Skin color is determined by: melanin, oxyhemoglobin, reduced hemoglobin, lipid, and carotene.
• Not only the proportions of these components affect the color, but also:
• Their depth within the skin
• The thickness of the epidermis
• Hydration
• TYNDALL EFFECT — modifies color of skin and lesions by the selective scattering of light waves of different wavelengths.
• Blue nevus and Mongolian spots are examples of this light-dispersion effect, in which brown melanin in the DERMIS appears BLUE-GRAY.

Diagnostic Value of Color

• There are many shades of pink, red, and purple, each tending to suggest a diagnosis or disease group.
• Violaceous — in White patients, interface reactions such as lichen planus or lupus erythematosus.
• Orange-red (salmon) — characteristic of pityriasis rubra pilaris, but may be CONCEALED in patients with darker skin tones (Fig. 2.12A and B).
• Yellow — lipid-containing lesions, as in xanthomas; this color is more difficult to see in darker skin (Fig. 2.13A and B).
• The constitutive color of the skin determines the quality of the color observed with a specific disorder.

Hypopigmentation vs. Depigmentation

• Patches lighter in color than normal skin may be completely DEpigmented or may have lost only part of their pigment (HYPOpigmented) — an important distinction.
• HYPOpigmented conditions: tinea versicolor, Hansen disease, ash-leaf macules of tuberous sclerosis, hypomelanosis of Ito, seborrheic dermatitis, and idiopathic guttate hypomelanosis.
• TRUE DEPIGMENTATION suggests: vitiligo, nevus depigmentosus, halo nevus, scleroderma, morphea, or lichen sclerosus.

Hyperpigmentation — Epidermal vs. Dermal

• May result from epidermal or dermal causes; may relate to increased melanin or to deposition of other substances.
• EPIDERMAL hyperpigmentation: nevi, melanoma, café au lait spots, melasma, and lentigines.
• These lesions ARE ACCENTUATED when examined with a Wood's light.
• DERMAL pigmentation: occurs after many inflammatory conditions (postinflammatory hyperpigmentation) or from deposition of metals, medications, medication-melanin complexes, or degenerated dermal material (ochronosis).
• These conditions are NOT enhanced when examined by a Wood's light.
• Hyperpigmentation following inflammation is most frequently the result of DERMAL MELANIN deposition, but in some conditions — such as lichen aureus — is caused by IRON.
• Dermal IRON deposition appears more YELLOW-BROWN or GOLDEN than dermal melanin.

• Palpation is an essential part of the physical examination of lesions. Key questions:
• Does the lesion blanch on pressure? If NOT, it may be PURPURIC.
• Is it fluctuant? If so, it may have free fluid in it.
• If there is a nodule or tumor, does it sink through a ring into the panniculus, like a neurofibroma?
• Is it hard enough for calcification to be suspected, or merely very firm, like a keloid or dermatofibroma?

• Certain conditions may be associated with increased or decreased sensation.
• Skin lesions of borderline and tuberculoid Hansen disease are typically ANESTHETIC IN THEIR CENTERS.
• Pain and tenderness on palpation are characteristic of:
• Neural tumors
• Edematous and inflamed lesions
• Complex regional pain syndrome
• In other neuropathic conditions, such as notalgia paresthetica, the patient may perceive BOTH pruritus AND hyperesthesia.
• Neurally mediated itch may be accompanied by other neural sensations, such as heat or burning.
• The combination of pruritus with other neural symptoms suggests involvement of NERVES in the pathologic process.

• Hair-bearing areas: involvement by certain skin disorders causes characteristic lesions.
• Discoid lupus causes scarring alopecia with characteristic dyspigmentation (scalp plaque with scarring alopecia, hyperpigmentation and depigmentation).
• On the skin, the lesions may be LESS characteristic.
• Diffuse hair loss may be seen in certain conditions, such as acrodermatitis enteropathica, and may be a clue to the diagnosis.
• Loss of hair WITHIN a skin lesion may suggest the diagnosis, such as the alopecia seen in the tumid plaques of follicular mucinosis.
• Nails: some skin disorders cause characteristic nail changes even when the periungual tissue is NOT involved.
• Pitting seen in psoriasis and alopecia areata may be useful in confirming these diagnoses when other findings are not characteristic.
• The nails and adjacent structures may be the SOLE site of pathology, as in candidal paronychia.
• Oral mucosa: the complete skin examination INCLUDES examination of the oral mucosa.
• Oral lesions are characteristically found in: viral syndromes (exanthems), lichen planus, HIV-associated Kaposi sarcoma (oral Kaposi sarcoma), and autoimmune bullous diseases (pemphigus vulgaris).

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• There are unique clinical considerations when examining and diagnosing skin disease in patients with different skin tones.
• Erythema perception: darker skin tones may make erythema difficult to perceive, leading to the impression that the condition is LESS SEVERE than it appears — as with rosacea, acne, and drug eruptions.
• Erythema may appear reddish-brown, violaceous, ashen gray, or dark brown.
• Concealed colors: the salmon color of pityriasis rubra pilaris and the yellow color of xanthomas may be concealed within brown and black skin tones (see Fig. 2.12A and B and Fig. 2.13A and B).
• Neoplasms: basal cell carcinomas, squamous cell carcinomas, and dermatofibroma protuberans are MORE LIKELY to be the PIGMENTED variety.
• Cutaneous T-cell lymphoma may be hypopigmented or have areas of hypopigmentation admixed with hyperpigmentation.
• Pruritic lesions in Black patients may evolve to be small, shiny, flat-topped papules with a violaceous or dark brown or black hue, from the combination of erythema and pigment incontinence.
• These lichenified lesions would be suspected of being LICHENOID by the untrained eye but may in fact be ECZEMATOUS.
• Distribution variation: perifollicular accentuation and an EXTENSOR rather than FLEXURAL distribution is common in Black patients with atopic dermatitis.
• In Asian patients, it may MIMIC PSORIASIS.

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• Patients at risk for the development of skin cancer should be taught the correct method of skin self-examination, specifically:
• The ABCDEs of melanoma detection
• The types of lesions that might represent basal cell carcinoma or squamous cell carcinoma

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• Primary Layers: Skin consists of 3 distinct functional layers: Epidermis, Dermis, and Subcutaneous tissue (Hypodermis).
• Skin Thickness Variations:
• Epidermis: Ranges from 0.05 mm on eyelids to 1.5 mm on palms and soles.
• Dermis: Ranges from 0.3 mm on eyelids to 3.0 mm on the back.
• Topography: Skin is thicker on dorsal/extensor surfaces than on ventral/flexor surfaces.

Epidermis (Stratified Squamous Epithelium)

• Stratum Basale (Basal Layer): Single row of columnar stem cells resting on basement membrane; continually divide to give rise to keratinocytes.
• Stratum Spinosum (Spinous Layer): Polyhedral keratinocytes tightly bound by intercellular bridges/desmosomes (seen histologically as spines); actively synthesize insoluble keratin proteins.
• Stratum Granulosum (Granular Layer): Cells flatten, cytoplasm accumulates basophilic keratohyalin granules; cells undergo programmed destruction of nuclei and organelles.
• Stratum Corneum (Horny Layer): Outermost physical barrier; composed of dead, anucleate, flattened, keratin-packed squames.
• Specialized Epidermal Cell Types:
• Melanocytes: Neural crest-derived dendritic cells in basal layer; synthesize melanin pigment inside melanosomes and transfer them to adjacent keratinocytes.
• Langerhans Cells: Bone marrow-derived dendritic cells; frontline antigen-presenting cells (APCs) responsible for cutaneous immune responses and contact hypersensitivity.
• Merkel Cells: Specialized basal layer mechanoreceptors attached to unmyelinated nerve terminals; responsible for light touch sensation.

Dermis (Connective Tissue Support)

• Connective Tissue Components: Composed of 3 major fiber types: Collagen (provides structural tensile strength), Elastic fibers (provides elasticity and recoil), and Reticular fibers.
• Dermal Layers:
• Papillary Layer: Thin upper dermal layer; interdigitates with epidermal rete ridges; composed of thin, haphazardly arranged collagen fibers.
• Reticular Layer: Thick lower dermal layer extending to subcutis; composed of thick collagen bundles arranged parallel to the skin surface.
• Cellular Components:
• Histiocytes: Wandering tissue macrophages that phagocytose and store hemosiderin, melanin, and inflammatory debris.
• Mast Cells: Perivascular cells; contain dense granules that manufacture and release histamine, heparin, and chemotactic factors during allergic reactions.

Dermal Nerves & Vasculature

• Mechanoreceptors:
• Meissner Corpuscles: Encapsulated tactile receptors in dermal papillae; detect light touch and low-frequency vibration.
• Vater-Pacini (Pacinian) Corpuscles: Large encapsulated deep dermal/subcutaneous receptors; detect deep pressure and high-frequency vibration.
• Free Nerve Endings: Unmyelinated nerve fibers in papillary dermis; receive sensations of pain, pruritus (itch), and temperature.
• Neurophysiology of Itch vs. Pain:
• Low-intensity stimulation of unmyelinated free nerve endings by inflammatory mediators → Pruritus (Itch).
• High-intensity stimulation of unmyelinated free nerve endings → Pain.
• Mechanism of Scratching: Scratching replaces the intolerable sensation of itch with a more tolerable sensation of mild pain, temporarily abolishing pruritus.
• Autonomic Innervation:
• Adrenergic (Sympathetic): Innervates cutaneous blood vessels (vasoconstriction), arrector pili muscles, and apocrine sweat glands.
• Cholinergic (Sympathetic): Innervates eccrine sweat glands.
• Sebaceous Glands: Regulated primarily by circulating androgenic endocrine hormones (NOT innervated by autonomic nerves).
• Cutaneous Vasculature: Dual vascular plexus system connected by vertical communicating vessels:
• Superficial (Subpapillary) Plexus: Located at base of papillary dermis; supplies capillary loops in dermal papillae.
• Deep Plexus: Located at dermo-subcutaneous junction.
• Function: Thermoregulation, nutrient supply, and inflammatory cell trafficking.

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• Diagnostic Challenges in Dermatology:

1. Hundreds of distinct cutaneous clinical entities exist.
2. Single diseases vary widely in appearance (e.g., seborrheic keratosis can be smooth, rough, eroded, or irregularly pigmented).
3. Skin diseases are dynamic and evolve over time (e.g., Herpes simplex: red papule → vesicle → erosion → crusted scar).

• Systematic 5-Step Diagnostic Approach:

1. History: Duration, onset rate, anatomical location, symptoms (itch/pain), family history, medications, allergies, occupation, prior treatments.
2. Distribution: Examine patient completely disrobed to establish total skin involvement pattern.
3. Primary Lesion Identification: Identify the initial un-manipulated primary lesion using handheld magnification or dermoscopy.
4. Differential Diagnosis: Formulate targeted differential diagnosis based on primary lesion morphology and regional pattern.
5. Diagnostic Testing: Perform targeted confirmatory tests (skin biopsy, KOH prep, scabies prep, Gram stain, fungal/bacterial culture, Tzanck smear, Wood's lamp, patch testing, darkfield examination, serology).

• Examination Technique: Divide body skin surface into defined anatomic sections and scan systematically; complete skin examination (TBSE) is recommended for all rash presentations.

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Macule

• Definition: A circumscribed, flat area of skin discoloration < 1 cm in diameter; non-palpable.
• Differential Diagnoses by Color:
• Brown/Hyperpigmented: Junctional nevus, lentigo, freckle (ephelis), flat seborrheic keratosis.
• Hypopigmented/White: Vitiligo, tinea versicolor, idiopathic guttate hypomelanosis, nevus anemicus, postinflammatory hypopigmentation.
• Red/Erythematous: Viral exanthem, drug eruption, petechiae, cherry angioma.

Patch

• Definition: A flat, non-palpable area of skin discoloration > 1 cm in diameter.
• Differential Diagnoses: Vitiligo, melasma, tinea versicolor, port-wine stain (nevus flammeus), large café-au-lait macule, morphea.

Papule

• Definition: An elevated, solid skin lesion < 1 cm in diameter.
• Differential Diagnoses by Surface / Color:
• Skin-Colored / Flesh-Colored: Intradermal nevus, verruca vulgaris, molluscum contagiosum, neurofibroma, basal cell carcinoma, sebaceous hyperplasia.
• Red/Erythematous: Acne papule, cherry angioma, insect bite, atopic dermatitis papule, polymorphic light eruption.
• Violaceous/Purple: Lichen planus, Kaposi sarcoma.
• Yellow: Xanthoma, sebaceous hyperplasia.

Plaque

• Definition: An elevated, solid, plateau-like superficial lesion > 1 cm in diameter; frequently formed by confluence of papules.
• Differential Diagnoses: Psoriasis vulgaris, lichen simplex chronicus, nummular eczema, tinea corporis, mycosis fungoides, pityriasis rubra pilaris.

Nodule

• Definition: A circumscribed, elevated, solid spherical or ovoid lesion > 1 cm in diameter, extending deeper into the dermis or subcutaneous tissue.
• Differential Diagnoses: Erythema nodosum, dermatofibroma, lipoma, epidermoid cyst, nodular basal cell carcinoma, nodular melanoma, rheumatoid nodule.

Tumor

• Definition: A large, solid cutaneous mass > 2 cm in diameter with depth into dermis/subcutis.
• Differential Diagnoses: Squamous cell carcinoma, nodular/metastatic melanoma, large lipoma, deep hemangioma, dermatofibrosarcoma protuberans.

Vesicle

• Definition: A fluid-filled, elevated, circumscribed blister < 1 cm in diameter.
• Differential Diagnoses: Herpes simplex, varicella-zoster, allergic contact dermatitis (poison ivy), pompholyx (dyshidrosis), dermatitis herpetiformis, vesicular tinea pedis.

Bulla

• Definition: A fluid-filled, elevated blister > 1 cm in diameter.
• Differential Diagnoses: Pemphigus vulgaris, bullous pemphigoid, bullous impetigo, toxic epidermal necrolysis (TEN), epidermolysis bullosa, severe thermal burn.

Pustule

• Definition: A circumscribed elevation of skin containing purulent exudate (pus).
• Differential Diagnoses: Acne vulgaris, folliculitis, pustular psoriasis, rosacea, dyshidrotic eczema (infected), subcorneal pustular dermatosis, pustular drug eruption.

Wheal (Hive)

• Definition: An evanescent, edematous papule or plaque caused by transient swelling of the papillary dermis; typically resolves within < 24 hours without residual scarring.
• Differential Diagnoses: Acute/chronic urticaria, dermatographism, urticarial vasculitis, insect bite reaction.

Cyst

• Definition: An encapsulated, elevated cavity lined with true epithelium, filled with liquid, mucinous, or semisolid keratinaceous material.
• Differential Diagnoses: Epidermoid cyst, pilar (trichilemmal) cyst, hidrocystoma, steatocystoma multiplex, digital mucous cyst.

Telangiectasia

• Definition: Permanently dilated, visible superficial capillaries or small blood vessels in the skin.
• Differential Diagnoses: Rosacea, chronic actinic damage, basal cell carcinoma, ataxia-telangiectasia, spider angioma, systemic sclerosis (scleroderma), topical corticosteroid atrophy.

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Scale (Desquamation)

• Definition: An abnormal accumulation or shedding of dead stratum corneum cells.
• Differential Diagnoses: Psoriasis (silvery white scale), seborrheic dermatitis (greasy yellow scale), tinea pedis/corporis, pityriasis rosea (collarette scale), ichthyosis vulgaris, asteatotic eczema.

Crust

• Definition: A dried exudate of blood, serum, or purulent material on the skin surface.
• Differential Diagnoses: Impetigo (classic honey-colored crust), ruptured herpes simplex/zoster, weeping eczema, ecthyma.

Erosion

• Definition: A focal, partial loss of epidermis; red, moist surface; heals WITHOUT scarring.
• Differential Diagnoses: Ruptured vesicle/bulla, perlèche (angular cheilitis), superficial excoriation, pemphigus vulgaris.

Ulcer

• Definition: A focal, full-thickness destruction of epidermis and at least part of the dermis; heals WITH scarring.
• Differential Diagnoses: Venous stasis ulcer, arterial ischemic ulcer, neuropathic (diabetic) ulcer, pyoderma gangrenosum, pressure injury.

Fissure

• Definition: A linear vertical cleavage or crack in the skin extending through epidermis into the dermis.
• Differential Diagnoses: Chapped lips, fingertip eczema, athlete's foot (interdigital tinea pedis), hyperkeratotic hand/foot eczema, perianal fissure.

Excoriation

• Definition: A linear or punctate excavation of epidermis caused by scratching, rubbing, or picking.
• Differential Diagnoses: Neurotic excoriation, prurigo nodularis, scabies, pediculosis, severe atopic dermatitis.

Atrophy

• Definition: Thinning of skin components.
• Epidermal Atrophy: Thin, translucent, "cigarette-paper" wrinkled skin with loss of skin markings.
• Dermal Atrophy: Depression of skin surface resulting from loss of dermal collagen or subcutaneous fat.
• Differential Diagnoses: Topical corticosteroid overuse, lichen sclerosus, striae distensae, discoid lupus erythematosus, morphea.

Lichenification

• Definition: Thickening of the epidermis with marked accentuation of normal skin surface markings, produced by chronic, repetitive rubbing or scratching.
• Differential Diagnoses: Lichen simplex chronicus, chronic atopic dermatitis, hypertrophic lichen planus.

Scar (Cicatrix) & Keloid

• Definition: Replacement of normal dermal architecture by dense fibrous connective tissue following cutaneous injury.
• Hypertrophic Scar: Elevated scar restricted strictly to original wound boundaries.
• Keloid: Nodular, exuberant fibrous scar tissue extending BEYOND original wound borders.

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• Comedo: Plugged pilosebaceous follicle containing keratin and sebum.
• Open Comedo (Blackhead): Orifice open to air; dark color from oxidized melanin and lipids.
• Closed Comedo (Whitehead): Orifice closed; pale cystic papule.
• Burrow: A thin, linear or serpiginous micro-tunnel in the stratum corneum produced by a parasite (Pathognomonic for Scabies [Mite: Sarcoptes scabiei]).
• Purpura / Petechiae / Ecchymosis: Extravasation of red blood cells into dermis; does NOT blanch under pressure (diascopy).
• Petechiae: Pinpoint purpuric macules < 3 mm.
• Purpura: Purpuric lesions 3–10 mm.
• Ecchymosis: Large purpuric macule/patch > 10 mm (bruise).
• Target (Iris) Lesion: Concentric round lesion with 3 distinct zones: central dark/vesicular zone, pale middle edematous ring, red outer erythematous halo (Pathognomonic for Erythema Multiforme).
• Koebner Phenomenon (Isomorphic Response): Development of typical disease lesions at sites of non-specific cutaneous trauma/scratching.
• Seen in: Psoriasis, Lichen Planus, Vitiligo, Verruca vulgaris, Molluscum contagiosum.
• Nikolsky Sign: Dislodgement of top layer of epidermis by applying light lateral shearing digital pressure.
• Positive in: Pemphigus vulgaris, Toxic Epidermal Necrolysis (TEN), Staphylococcal Scalded Skin Syndrome (SSSS).
• Auspitz Sign: Punctate pinpoint bleeding appearing after lifting/peeling scaly plaque in Psoriasis (due to rupture of exposed, dilated capillaries in elongated dermal papillae).
• Darier Sign: Rapid formation of a localized urticarial wheal and flare after mechanical rubbing of a lesion (Pathognomonic for Cutaneous Mastocytosis / Urticaria Pigmentosa).

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• Scalp: Seborrheic dermatitis, psoriasis, tinea capitis, alopecia areata, androgenetic alopecia, folliculitis decalvans, pediculosis capitis.
• Face: Rosacea, acne vulgaris, seborrheic dermatitis, systemic lupus erythematosus (malar rash), contact dermatitis, actinic keratosis, basal cell carcinoma.
• Eyelids: Atopic dermatitis, allergic contact dermatitis (cosmetics/nail polish), seborrheic dermatitis, xanthelasma, chalazion.
• External Ear: Seborrheic dermatitis, psoriasis, contact dermatitis (earring nickel), actinic keratosis, gouty tophi, chondrodermatitis nodularis chronica helicis.
• Lips & Oral Cavity: Herpes simplex (labialis), angular cheilitis (perlèche), actinic cheilitis, aphthous stomatitis, oral lichen planus, leukoplakia, squamous cell carcinoma.
• Neck: Atopic dermatitis, contact dermatitis (perfume/necklaces), tinea versicolor, pseudofolliculitis barbae, acrochordons (skin tags).
• Trunk: Pityriasis rosea, psoriasis, tinea versicolor, secondary syphilis, nummular eczema, viral exanthem, seborrheic keratosis.
• Axillae: Erythrasma (Corynebacterium minutissimum), inverse psoriasis, hidradenitis suppurativa, contact dermatitis (deodorant), tinea corporis, candidiasis.
• Groin / Inguinal Folds: Tinea cruris (spares scrotum), candidiasis (beefy red, satellite pustules, involves scrotum), inverse psoriasis, erythrasma (coral-red fluorescence under Wood's lamp).
• Genitalia: Lichen sclerosus, condyloma acuminata (HPV), herpes simplex, primary chancre (syphilis), scabies, extramammary Paget disease, squamous cell carcinoma.
• Hands (Palms & Dorsum): Irritant/allergic contact dermatitis, pompholyx, tinea manuum, palmar psoriasis, keratolysis exfoliativa, erythema multiforme.
• Feet & Soles: Tinea pedis, juvenile plantar dermatosis, plantar verruca, dyshidrotic eczema, palmoplantar pustulosis.
• Nails: Onychomycosis, nail psoriasis (pitting, oil drop sign, subungual hyperkeratosis, onycholysis), paronychia, lichen planus (pterygium), Pseudomonas infection (green nail).
• Lower Legs: Stasis dermatitis, pretibial myxedema, erythema nodosum, asteatotic eczema, necrobiosis lipoidica, venous/arterial leg ulcers.

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