Propylthiouracil-induced antineutrophil cytoplasm antibody-positive anaphylactoid purpura-like vasculitis--a case report.

Propylthiouracil (PTU), a drug commonly used for treatment of hyperthyroidism, is associated with various rare side effects. Antineutrophil cytoplasm antibody (ANCA)-positive vasculitis is a relatively unusual complication among them. The pathogenesis of ANCA-positive vasculitis during PTU therapy is still obscure. We present the case of a 12-year-old boy who developed ANCA-positive vasculitis during PTU therapy for Graves' disease. His symptoms and signs were indistinguishable from anaphylactoid purpura, a common small-vessel vasculitis in children. The clinical manifestations improved after discontinuation of PTU and immunosuppressant treatment. He remained symptom-free at 11-months follow-up.