A man with interstitial pneumonia due to propylthiouracil.

A 50-year-old Japanese man with Grave's disease had been taking propylthiouracil (PTU) for 10 years prior to the diagnosis of pneumonia. He noticed dyspnea on exertion and had a dry cough for at least 2 years and then suddenly developed high fever and dyspnea at rest. Clinical symptoms, chest radiographs, chest computed tomography and lung function revealed interstitial pneumonia. The symptoms were completely resolved after withdrawal of PTU, and consequently he was diagnosed with PTU-induced interstitial pneumonia. He also showed moderate myeloperoxidase (MPO)- antineutrophil cytoplasmic antibody (ANCA) positivity without any signs of vasculitis before as well as after PTU withdrawal. Although PTU-induced interstitial pneumonia is quite rare, with only 3 cases, including the present patient, so far reported, respiratory involvement should be considered in patients treated with PTU.