Propylthiouracil (PTU) can effectuate antineutrophil cytoplasmic antibodies (ANCA)-positive vasculitis. We report a case of severe, PTU-induced leucocytoclastic vasculitis with diffuse pulmonary hemorrhage within a month of initiating PTU. Emergent plasmapheresis was initiated with excellent clinical response. A clinical suspicion for this potential side effect coupled with early cessation of the drug is generally adequate. Clinical manifestations, posited pathogenetic mechanisms, and therapeutic strategies, including the role of plasmapheresis, are discussed.