51 GENERAL EXAMINATION OF THE SKIN
Harrison’s Manual of Medicine
GENERAL EXAMINATION OF THE SKIN
Additional Diagnostic Procedures
As dermatologic evaluation relies heavily on the objective cutaneous appearance, physical examination is often performed prior to taking a complete history in pts presenting with a skin problem. A differential diagnosis can usually be generated on the basis of a thorough examination with precise descriptions of the skin lesion(s) and narrowed with pertinent facts from the history. Laboratory or diagnostic procedures are then used, when appropriate, to clarify the diagnosis.
Examination of skin should take place in a well-illuminated room with pt completely disrobed. Helpful ancillary equipment includes a hand lens and a pocket flashlight to provide peripheral illumination of lesions. The examination often begins with an assessment of the entire skin viewed at a distance, which is then narrowed down to focus on the individual lesions.
DISTRIBUTION As illustrated in Fig. 51-1, the distribution of skin lesions can provide valuable clues to the identification of the disorder. Generalized (systemic diseases); sun-exposed (SLE, photoallergic, phototoxic, polymorphous light eruption, porphyria cutanea tarda); dermatomal (herpes zoster); extensor surfaces (elbows and knees in psoriasis); flexural surfaces (antecubital and popliteal fossae in atopic dermatitis).
FIGURE 51-1A, B, C and D. The distribution of some common dermatologic diseases and lesions.
ARRANGEMENT AND SHAPE Can describe individual or multiple lesions.
Linear [contact dermatitis such as poison ivy, lesions that appear at sites of local skin trauma (Koebner phenomenon)]; annular—“ring-shaped” lesion with an active border and central clearing (erythema chronicum migrans, erythema annulare centrificum, tinea corporis); iris or target lesion—two or three concentric circles of differing hue (erythema multiforme); circinate—circular lesion (urticaria, herald patch of pityriasis rosea); nummular—“coin-shaped” (nummular eczema); guttate—droplike (guttate psoriasis); morbilliform—“measles-like” with small confluent papules coalescing into unusual shapes (measles, drug eruption); reticulated—“netlike” (livedo reticularis); herpetiform— grouped vesicles, papules, or erosions (herpes simplex).
PRIMARY LESIONS Cutaneous changes caused directly by disease process.
Macule—a flat circumscribed lesion of a different color, allowing for differentiation from surrounding skin; patch—macule >2 cm in diameter; papule—elevated, circumscribed lesion of any color <1 cm in diameter, with the major portion of lesion projecting above surrounding skin; nodule—palpable lesion similar to a papule but >1 cm in diameter; plaque—an elevated, flat- topped lesion >1 cm in diameter; vesicle—sharply marginated elevated lesion <1 cm in diameter filled with clear fluid; bulla—vesicular lesion >1 cm in diameter; pustule—a well-marginated focal accumulation of inflammatory cells within skin; wheal—a transient elevated lesion due to accumulation of fluid in upper dermis; cyst—lesion consisting of liquid or semisolid material contained within limits of cyst wall (true cyst).
SECONDARY LESIONS Changes in area of primary pathology often due to secondary events, e.g., scratching, secondary infection, bleeding.
Scale—a flaky accumulation of excess keratin that is partially adherent to skin; crust—a circumscribed collection of inflammatory cells and dried serum on skin surface; excoriation—linear, angular erosions caused by scratching; erosion—a circumscribed, usually depressed, moist lesion resulting from loss of overlying epidermis; ulcer—a deeper erosion involving epidermis plus underlying papillary dermis; may leave a scar on healing; atrophy: (1) epidermal—thinning of skin with loss of normal skin surface markings, (2) dermal—depression of skin surface due to loss of underlying collagen or dermal ground substance; lichenification—thickening of skin with accentuation of normal skin surface markings most commonly due to chronic rubbing; scar—collection of fibrous tissue replacing normal dermal constituents.
OTHER DESCRIPTIVE TERMS Color, e.g., violaceous, erythematous; physical characteristics, e.g., warm, tender; sharpness of edge, surface contour—flat-topped, pedunculated (on a stalk), verrucous (wartlike), umbilicated (containing a central depression).
A complete history should be obtained, with special attention being paid to the following points:
Evolution of the lesion—site of onset, manner in which eruption progressed or spread, duration, periods of resolution or improvement in chronic eruptions
Symptoms associated with the eruption—itching, burning, pain, numbness; what has relieved symptoms; time of day when symptoms are most severe
Current or recent medications—both prescription and over-the-counter
Associated systemic symptoms (e.g., malaise, fatigue, arthralgias)
Ongoing or previous illnesses
History of allergies
Presence of photosensitivity
Review of systems
ADDITIONAL DIAGNOSTIC PROCEDURES
POTASSIUM HYDROXIDE PREPARATION Useful for detection of dermatophyte or yeast. Scale is collected from advancing edge of a scaling lesion by gently scraping with side of a microscope slide. Nail lesions are best sampled by trimming back nail and scraping subungual debris. A drop of 10– 15% potassium hydroxide is added to slide, and cover slip is applied. The slide may be gently heated and examined under microscope. Positive preparations show translucent, septate branching hyphae among keratinocytes.
TZANCK PREPARATION Useful for determining presence of herpes viruses. Optimal lesion to sample is an early vesicle. Lesion is gently unroofed with no. 15 scalpel blade, and base of vesicle is gently scraped with belly of blade (keep blade perpendicular to skin surface to prevent laceration). Scrapings are transferred to slide and stained with Wright’s or Giemsa stain. A positive preparation has multinucleate giant cells.
SKIN BIOPSY Minor surgical procedure. Choice of site very important.
DIASCOPY Assesses whether a lesion blanches with pressure. Done by pressing a magnifying lens or microscope slide on lesion and observing changes in vascularity. For example, hemangiomas will usually blanch; purpuric lesions will not.
WOOD’S LIGHT EXAMINATION Useful for detecting bacterial or fungal infection or accentuating features of some skin lesions.
PATCH TESTS To document cutaneous sensitivity to specific antigens.
For a more detailed discussion, see Lawley TJ, Yancey KB: Approach to the Patient with a Skin Disorder, Chap. 55, p. 305, in HPIM-15.