Drug-induced Pleuritis Associated with Hachimijiogan

Abstract

A 78-year-old man presented to our hospital with left-sided pleural effusion. A diagnosis could not be established based on blood or pleural fluid analyses. A re-evaluation of his medical history revealed that he had begun taking hachimijiogan five months prior to presentation. Pleural effusion resolved after discontinuation of hachimijiogan, resulting in a diagnosis of drug-induced pleuritis. Subsequently, an accidental rechallenge was performed to confirm the diagnosis. Drug-induced pleuritis due to Kampo medicines is uncommon, with no prior reports of hachimijiogan being associated with this condition. Obtaining a detailed medication history is essential for diagnosing pleural effusions of unknown etiology.