Antineutrophil cytoplasmic antibody (ANCA)-positive cutaneous leukocytoclastic vasculitis induced by propylthiouracil confirmed by positive patch test: a case report and review of the literature.

A 43-year-old female with antiphospholipid syndrome and Graves' disease developed a cutaneous leukocytoclastic vasculitis associated with antineutrophil cytoplasmic antibody (ANCA) against myeloperoxidase (MPO-ANCA) and proteinase-3 (PR3-ANCA), whilst treated with propylthiouracil (PTU). The skin lesions were progressively resolved after withdrawal of PTU and treatment with oral steroids. Patch testing with PTU at 1%, 5%, and 10% in petrolatum was positive at 48 h. Despite positive ANCA titers after 1 year of follow-up, the patient maintains complete clinical remission. PTU is a common antithyroid drug, which has been known to induce ANCA-positive vasculitis. Although most patients with this rare side effect have a good outcome, some fatal cases have been reported. Therefore, patients treated with PTU should be carefully followed and monitored, not only for their thyroid state but also for early detection of potential serious complications of this drug. Early diagnosis and prompt cessation of PTU therapy are essential to improve the outcome. Also key aspects of PTU-induced ANCA-positive vasculitis are reviewed.