Antineutrophil cytoplasmic antibody positive alveolar haemorrhage during propylthiouracil therapy for hyperthyroidism

Abstract: Recently, propylthiouracil (PTU) has been thought to be one of the possible causes of antineutrophil cytoplasmic antibody (ANCA)‐associated small vessel vasculitis syndrome, resulting in glomerulonephritis and, infrequently, diffuse alveolar haemorrhage (DAH). The mechanism of ANCA‐positive vasculitis during PTU therapy is still unknown. Herein, we describe the case of a 59‐year‐old woman who developed myeloperoxidase (MPO)‐ and proteinase 3 (PR3)‐ANCA positive DAH, without any other organ system involvement, during PTU therapy. Diminution and discontinuation of PTU resulted in a positive response. To our knowledge, this is the first documentation of both MPO‐ and PR3‐ANCA‐positive DAH, without systemic manifestations, developing during PTU therapy.