Unusual urticarias.

Typical urticarial lesions are transient cutaneous swellings of sudden onset, often itchy, persisting for less than 24 hours and resolving to leave normal appearing skin. Angioedema lesions are similar subcutaneous lesions. Atypical urticarias persist for longer than 24 hours, may be painful and bruised in appearance and accompanied with severe systemic symptoms. Conditions where prolonged weals are present include delayed pressure urticaria and urticarial vasculitis. These conditions do not respond well to antihistamine therapy. In delayed pressure urticaria, weals appear after a delay of hours at sites of sustained pressure on the skin and occur in association with ordinary chronic 'idiopathic' urticaria. Weals of urticarial vasculitis show histological features of venulitis, and can be accompanied by arthralgia and abdominal pain. Rarely, the condition is due to infective or autoimmune disease. Urticarial diseases, sometimes with features of urticarial vasculitis, and with associated systemic features include Schnitzler's Syndrome, Still's disease and Muckle-Wells syndrome. The latter syndrome is linked with chromosome 1q44, as is autosomal dominant cold urticaria, an unusual physical urticaria. Persistent cholinergic erythema, a variant of cholinergic urticaria, has been mistaken for a drug eruption or cutaneous mastocytosis. Rarely, food and exercise induced urticaria and anaphylaxis occur when exercise follows a specific food or any meal within a few hours. The early stages of inflammatory disease may be mistaken for urticaria and angioedema, but lesions usually persist for longer than 48 hours and are accompanied by epidermal changes.