Carbimazole, an antithyroid drug, is associated with a significant number of side effects, but pleuropulmonary complications are rare. We report the case of a 42-year-old Caucasian man who developed dyspnoea secondary to bilateral exudative pleural effusions while on carbimazole therapy. Extensive investigations, including a vasculitic screen, ruled out other potential causes for this patient's clinical presentation. This patient's pleural effusions gradually resolved within a few months of stopping carbimazole therapy, suggesting a role for the latter in the aetiopathogenesis of his presentation. Clinicians should consider discontinuing treatment with carbimazole and introducing alternative antithyroid therapy in this setting, once other potential causes of a pleural effusion have been systematically ruled out.
2016 BMJ Publishing Group Ltd.