Psoriasis (Table 53-2) Psoriasis is one of the most common dermatologic diseases, affecting up to 1% of the world's population. It is a chronic inflammatory skin disorder clinically characterized by erythematous, sharply demarcated papules and rounded plaques, covered by silvery micaceous scale. The skin lesions of psoriasis are variably pruritic. Traumatized areas often develop lesions of psoriasis (Koebner or isomorphic phenomenon). Additionally, other external factors may exacerbate psoriasis including infections, stress, and medications (lithium, beta blockers, and antimalarials). Table 53-2 Papulosquamous Disorders Clinical Features Other Notable Features Histologic Features Psoriasis Sharply demarcated, May be aggravated Acanthosis, by vascular erythematous plaques certain with mica-like scale; infection; predominantly elbows, severe knees,. | Chapter 053. Eczema and Dermatitis Part 6 Psoriasis Table 53-2 Psoriasis is one of the most common dermatologic diseases affecting up to 1 of the world s population. It is a chronic inflammatory skin disorder clinically characterized by erythematous sharply demarcated papules and rounded plaques covered by silvery micaceous scale. The skin lesions of psoriasis are variably pruritic. Traumatized areas often develop lesions of psoriasis Koebner or isomorphic phenomenon . Additionally other external factors may exacerbate psoriasis including infections stress and medications lithium beta blockers and antimalarials . Table 53-2 Papulosquamous Disorders Clinical Features Other Notable Features Histologic Features Psoriasis Sharply demarcated erythematous plaques with mica-like scale predominantly elbows knees and scalp atypical forms may localize to intertriginous areas eruptive forms may be associated with infection May be aggravated by certain drugs infection severe forms seen associated with HIV Acanthosis vascular proliferation Lichen planus Purple polygonal papules marked by severe pruritus lacy white markings especially associated with mucous membrane lesions Certain drugs may induce thiazides antimalarial drugs Interface dermatitis Pityriasis rosea Rash often preceded by herald patch oval to round plaques with trailing scale most often affects the trunk and eruption lines up in skin folds giving a fir tree -like appearance generally spares palms and soles Variable pruritus selflimited resolving in 2- 8 weeks may be imitated by secondary syphilis Pathologic features often .
