[Allergic vasculitis in children].

Allergic vasculitis is characterized clinically by vascular purpura and histologically by leukocytoclastic angiitis of the small vessels in the middle and superficial dermis. Extra-cutaneous lesions may occur. Among them, the most common are joint manifestations. Renal involvement governs the prognosis. Circulating immune complexes probably contribute to the development of lesions, although this role has not been firmly established. Cellular immunity is probably also involved. A large number of factors may trigger the development of allergic vasculitis. Clinical patterns vary widely across patients. In 50% of patients no cause is identified. In children, Henoch-Schönlein purpura and infections (viral or bacterial) are the most common "causes". The ideal treatment would be elimination of the causative allergen. However this is often impossible to achieve and a variety of symptomatic treatments (rest, dapsone, colchicine, corticosteroids, immunosuppressants...) may be discussed according to the severity of clinical manifestations. Effectiveness of these treatments is variable.