Chronic plaque-type psoriasis (Figures 2A and 2B), the most common variant, is characterized by sharply demarcated pink papules and plaques with a silvery scale in a symmetric distribution on the extensor surfaces, scalp, trunk, and lumbosacral areas.
Guttate psoriasis (FIGURE 3) features small (often < 1 cm) pink scaly papules that appear suddenly. It is more commonly seen in children and is usually preceded by an upper respiratory tract infection, often with Streptococcus.10 If strep testing is positive, guttate psoriasis may improve after appropriate antibiotic treatment.
Erythrodermic psoriasis (FIGUREs 4A and 4B) involves at least 75% of the body with erythema and scaling.11 Erythroderma can be caused by many other conditions such as atopic dermatitis, a drug reaction, Sezary syndrome, seborrheic dermatitis, and pityriasis rubra pilaris. Treatments for other conditions in the differential diagnosis can potentially make psoriasis worse. Unfortunately, findings on a skin biopsy are often nonspecific, making careful clinical observation crucial to arriving at an accurate diagnosis.
Pustular psoriasis is characterized by bright erythema and sterile pustules. Pustular psoriasis can be triggered by pregnancy, sudden tapering of corticosteroids, hypocalcemia, and infection. Involvement of the palms and soles with severe desquamation can drastically impact daily functioning and quality of life.
Inverse or flexural psoriasis (FIGUREs 5A and 5B) is characterized by shiny, pink-to-red sharply demarcated plaques involving intertriginous areas, typically the groin, inguinal crease, axilla, inframammary regions, and intergluteal cleft.
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