Propylthiouracil-induced vasculitis with alveolar hemorrhage after 31 years of treatment: a case report.

Background: Propylthiouracil is an antithyroid medication that is associated with ANCA positivity, often in the absence of clinically overt vasculitis. Propylthiouracil-induced ANCA-associated vasculitis (AAV) is characterized by multiple antigenicity and presents similarly to other forms of drug-induced vasculitis.

Case presentation: We report a case of a 49-year-old woman who developed propylthiouracil-induced AAV after 31 years of intermittent therapy. The patient presented with progressive respiratory and generalized symptoms. She was diagnosed with propylthiouracil-induced AAV with alveolar hemorrhage based on detection of ANCA and anti-MPO antibodies, exclusion of primary vasculitis, and symptom resolution following propylthiouracil withdrawal. The patient was treated with intravenous methylprednisolone, followed by oral prednisolone. Her symptoms resolved, and her laboratory and radiological tests improved within one week.

Conclusions: Research linking the duration of propylthiouracil use to the development of vasculitis is restricted by multiple methodological limitations. Maintaining a high index of clinical suspicion is a more reliable approach to detecting propylthiouracil-induced AAV than regular laboratory monitoring, given that patients with Graves' disease may show ANCA positivity in the absence of medication use. Therefore, clinicians should remain vigilant for the varied presentations of propylthiouracil-induced AAV. Moreover, further research is recommended to investigate the possible link between the duration of PTU use and the onset of clinically overt vasculitis.