Development of Propionibacterium acnes-associated Sarcoidosis During Etanercept Therapy

Although numerous recent studies have reported the development of sarcoidosis in patients treated with tumor necrosis factor alpha (TNF-α) inhibitors, it is unclear whether the pathogenesis of drug-induced sarcoidosis is identical to that of spontaneous sarcoidosis. We herein present the case of a patient who developed sarcoidosis 6 months after the introduction of etanercept as treatment for rheumatoid arthritis. Typical clinical symptoms with noncaseating epithelioid granulomas detected in a mediastinal lymph node specimen were consistent with the diagnosis of sarcoidosis. Immunohistochemistry revealed Propionibacterium acnes in the noncaseating granulomas. The present findings suggest that Propionibacterium acnes is a cause of sarcoidosis, even when the disease is induced by TNF-α inhibitors.