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Accurate diagnosis of cutaneous disease in infants and children is a systematic process that requires careful inspection, evaluation, and some knowledge of dermatologic terminology and morphology to develop a prioritized differential diagnosis. The manifestations of skin disorders in infants and young children often vary from those of the same diseases in older children and adults. The diagnosis may be obscured, for example, by different reaction patterns or a tendency toward easier blister formation. In addition, therapeutic dosages and regimens often differ from those of adults, with medications prescribed on a “per kilogram” (/kg) basis and with liquid formulations. Nevertheless, the same basic principles that are used to detect disorders affecting viscera apply to the detection of skin disorders. An adequate history should be obtained, a thorough physical examination performed, and, whenever possible, the clinical impression verified by appropriate laboratory studies. The easy visibility of skin lesions all too often results in a cursory examination and hasty diagnosis. Instead, the entire skin should be examined routinely and carefully, including the hair, scalp, nails, oral mucosa, anogenital regions, palms, and soles, because visible findings often hold clues to the final diagnosis. The examination should be conducted in a well-lit room. Initial viewing of the patient at a distance establishes the overall status of the patient and allows recognition of distribution patterns and clues to the appropriate final diagnosis. This initial evaluation is followed by careful scrutiny of primary and subsequent secondary lesions in an effort to discern the characteristic features of the disorder. Although not always diagnostic, the morphology and configuration of cutaneous lesions are of considerable importance to the classification and diagnosis of cutaneous disease. A lack of understanding of dermatologic terminology commonly poses a barrier to the description of cutaneous disorders by clinicians who are not dermatologists. Accordingly, a review of dermatologic terms is included here (Table 1.1). The many examples to show primary and secondary skin lesions refer

Configuration of Lesions

A number of dermatologic entities assume annular, circinate, or ring shapes and are interpreted as ringworm or superficial fungal infections. Although tinea is a common annular dermatosis of childhood, there are multiple other disorders that must be included in the differential diagnosis of ringed lesions, including pityriasis rosea, seborrheic dermatitis, nummular eczema, lupus erythematosus, granuloma annulare, annular psoriasis, erythema multiforme, erythema annulare centrifugum, erythema migrans, secondary syphilis, sarcoidosis, urticaria, pityriasis alba, tinea versicolor, lupus vulgaris, drug eruptions, and cutaneous T-cell lymphoma. The terms arciform and arcuate refer to lesions that assume arc-like configurations. Arciform lesions may be seen in erythema multiforme, urticaria, pityriasis rosea, bullous dermatosis of childhood, and sometimes epidermolysis bullosa simplex.Lesions that tend to merge are said to be confluent. Confluence of lesions is seen, for example, in childhood exanthems, Rhus dermatitis, erythema multiforme, tinea versicolor, and urticaria. Lesions localized to a dermatome supplied by one or more dorsal ganglia are referred to as dermatomal. Herpes zoster classically occurs in a dermatomal distribution. Discoid is used to describe lesions that are solid, moderately raised, and disc shaped. The term has largely been applied to discoid lupus erythematosus, in which the discoid lesions usually show atrophy and dyspigmentation. Discrete lesions are individual lesions that tend to remain separated and distinct. Eczematoid and eczematous are adjectives relating to inflamed, dry skin with a tendency to thickening, oozing, vesiculation, and/or crusting; although atopic dermatitis is a classic eczematous disorder, other examples of eczema are contact, nummular, and dyshidrotic forms. Grouping and clustering are characteristic of vesicles of herpes simplex or herpes zoster, insect bites, lymphangioma circumscriptum, contact dermatitis, and bullous dermatosis of childhood. Guttate or drop-like lesions are characteristic of flares of psoriasis in children and adolescents that follow an acute upper respiratory tract infection, usually streptococcal. Gyrate refers to twisted, coiled, or spiral-like lesions, as may be seen in patients with urticaria and erythema annulare centrifugum. Iris or target-like lesions are concentric ringed lesions characteristic of erythema multiforme. The classic “targets” in this condition are composed of a central dusky erythematous papule or vesicle, a peripheral ring of pallor, and then an outer bright red ring. Keratosis refers to circumscribed patches of horny thickening, as seen in seborrheic or actinic keratoses, keratosis pilaris, and keratosis follicularis (Darier disease). Keratotic is an adjective pertaining to keratosis and commonly refers to the epidermal thickening seen in chronic dermatitis and callus formation. The Koebner phenomenon or isomorphic response refers to the appearance of lesions along a site of injury. The linear lesions of warts and molluscum contagiosum, for example, occur from autoinoculation of virus from scratching; those of Rhus dermatitis (poison ivy) result from the spread of the plant’s oleoresin. Other examples of disorders that show a Koebner phenomenon are psoriasis, lichen planus, lichen nitidus, pityriasis rubra pilaris, and keratosis follicularis (Darier disease). Lesions in a linear or band-like configuration appear in the form of a line or stripe and may be seen in epidermal nevi, Conradi syndrome, linear morphea, lichen striatus, striae, Rhus dermatitis, deep mycoses (sporotrichosis or coccidioidomycosis), incontinentia pigmenti, pigment mosaicism, porokeratosis of Mibelli, or factitial dermatitis. In certain genetic and inflammatory disorders, such linear configurations represent the lines of Blaschko, which trace clones of embryonic epidermal cells and, as such, represent a form of cutaneous mosaicism. This configuration presents as a linear pattern on the extremities, wavy or S-shaped on the lateral trunk, V-shaped on the central trunk, and varied patterns on the face and scalp.