| Inflammatory |
| Atopic dermatitis | Common M ≥ F Age: usually presents in childhood, but may persist | Pruritic. Chronic course with exacerbations Usually worse in winter Family or personal history of atopy | Infants: red papules, scaly plaques, and excoriations on extensor arms Children and adults: red lichenified plaques, prurigo nodules, and excoriations on flexor arms, especially antecubital fossae (Figure 8-8) |
| Keratosis pilaris | Very common. Often seen with atopic dermatitis | Usually asymptomatic. Rarely, mildly pruritic | Follicular-based keratotic papules with peripheral erythema. Stippled or "goosebumps" appearance on extensor surfaces (Figure 8-9) |
| Allergic contact dermatitis | Common F > M Age: any age | Pruritic and painful fissures. Onset is hours to days after contact with allergen | Acute: papules and vesicles on an erythematous base (Figures 8-4 and 8-5) Chronic: xerosis, fissuring, hyperpigmentation, and lichenification at sites of direct contact with allergen (Figure 8-6) |
| Psoriasis vulgaris | Common. M = F Onset at any age but peaks in 20s and 50s | Asymptomatic or mildly pruritic. Chronic Associated with arthritis Family history of psoriasis | Red papules and plaques with silvery, thick, adherent scale on elbows and extensor surface (Figure 9-1) |
| Lichen planus | Uncommon F > M Age: 30-60 years | Pruritic or symptomatic Lasts months to years May be drug-induced or associated with hepatitis C | Classically flat-topped, well-defined, polygonal, violaceous, shiny papules on volar wrist and flexor arms (Figures 9-10 and 9-11) |
| Lichen simplex chronicus | Common F > M Age >20 years. More common in atopic patients | Paroxysmal episodes of pruritus disproportionate to external stimuli (eg, changing clothes). Emotional stress may exacerbate | Sharply defined round, oval, or linear plaque(s) comprised of confluent dull pink-red papules with excoriations on extensor arms (Figure 8-13) |
| Nummular eczema | Common M > F Age: bimodal; peaks in young adults and the elderly | Pruritic Chronic waxing and waning course Associated with dry skin | Round, light pink, scaly, thin, 1-3 cm plaques on extensor arms (Figure 8-11) |
| Infectious |
| Tinea corporis | Common M:F unknown Age: all. More common in hot humid areas, farms, and crowded living conditions | Mild pruritus History of contact with infected people or animals. Outbreaks seen in daycare facilities, schools, and wrestlers | Solitary or grouped well-demarcated red annular plaques with raised border with peripheral scale (Figure 10-4) |
| Photodermatoses. See Chapter 31 (Skin Diseases of the Face) |