Psoriasis
Psoriasis is a chronic, relapsing, immune-mediated dermatosis of accelerated keratinocyte turnover, classically presenting as sharply demarcated, silvery-scaled plaques on extensor surfaces, with guttate, inverse, pustular, and erythrodermic variants and an associated psoriatic arthritis. Mild-to-moderate disease is treated with emollients and topical corticosteroids with or without a vitamin-D analogue (calcipotriene 0.005% twice daily), while widespread (over 10% body surface area), recalcitrant, or severe disease escalates to phototherapy, methotrexate (weekly single dose 7.5 to 25 mg), or a biologic such as adalimumab, ustekinumab, or secukinumab, never a systemic glucocorticoid.
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What this article covers
- Overview
Definition: psoriasis is a chronic, relapsing, immune-mediated dermatosis driven by keratinocyte hyperproliferation, producing sharply demarcated erythematous plaques with silvery-white scale.
- Epidemiology
Common: psoriasis affects approximately 2 to 4 percent of the adult population.
- Risk factors
Family history of psoriasis: supports the diagnosis when skin findings are ambiguous.
- Pathophysiology
Immune-mediated keratinocyte hyperproliferation: chronic, immune-driven accelerated epidermal turnover is the core process producing the thickened, scaling plaque.
- Clinical features
Plaque psoriasis, the diagnostic anchor: sharply marginated erythematous papules/plaques with thick, silvery-white (micaceous) scale and a crisp border, unlike the fuzzy fade-out of eczema.
- Differential diagnosis
Tinea corporis: clears centrally with an active, scaling leading edge, unlike the uniform, non-clearing plaque of psoriasis; potassium hydroxide preparation of the edge distinguishes the two.
- Diagnosis
Diagnosis is clinical: sharply demarcated plaques with silvery scale in the classic extensor/scalp distribution plus a positive Auspitz sign establish the diagnosis in typical cases; biopsy is reserved for atypical presentations.
- Management
First, classify severity by body surface area and site: mild-to-moderate localized disease is treated topically, while disease over 10 percent body surface area, recalcitrant disease, or disease at…
- Complications
Erythrodermic psoriasis: loss of heat, fluid, and electrolytes across a failing skin barrier, capable of driving high-output cardiac failure.
- Prognosis
Chronic, relapsing course: lifelong for most patients, though guttate psoriasis is often self-limited or converts to plaque disease within months.
- Prevention
Avoid systemic glucocorticoids and abrupt antipsoriatic drug withdrawal, the classic preventable trigger of erythrodermic and pustular flare.
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