[Hypersensitivity reaction to allopurinol].

Major hypersensitivity reactions to allopurinol are rare. They are characterized by systemic vasculitis associated with a grave clinical picture. 20 days after beginning treatment with allopurinol, a 70-year-old patient presented with a maculo-papular, erythemato-squamous eruption which developed into erythroderma with fever, edema, polyadenopathy, marked eosinophilia, cholostatic jaudice, and aggravation of preexisting renal insufficiency.