Cryptogenic organizing pneumonia secondary to carbimazole use

ABSTRACT Cryptogenic organizing pneumonia (COP) is an interstitial lung disease that can arise without a known cause or as a result of factors like radiation, respiratory infections, or certain medications. In this report, we discuss a 60-year-old woman who experienced shortness of breath and a productive cough for one week. Her medical history includes Graves’ disease, for which she had been taking carbimazole 5 mg daily for four months. A chest CT scan revealed a halo sign indicative of COP. No other potential cause for COP was found aside from carbimazole. Although the patient did not develop leukopenia or agranulocytosis, the clinical course was compatible with a non-bone-marrow-mediated, idiosyncratic drug-induced lung injury: symptoms developed after carbimazole initiation, infectious and autoimmune causes were excluded, and radiographic findings improved after drug withdrawal and glucocorticoid therapy. This case underscores a link between COP and carbimazole use, suggesting that the medication can induce COP. We further expand on causality assessment, differential diagnosis, and previously reported cases of antithyroid-drug-associated COP to strengthen clinical applicability.