Kakkonto-Induced Pneumonitis: A Case Report

A 76-year-old woman with a history of polymyalgia rheumatica, dyslipidemia, and osteoporosis was admitted due to a one-week history of productive cough and was initially diagnosed with bacterial pneumonia. Despite antibiotic therapy, her clinical condition worsened, leading to respiratory failure. Further history-taking revealed that she had been taking kakkonto, a Japanese herbal medicine (JHM), for the preceding 4.5 months as a self-initiated measure to prevent infection. The patient was eventually diagnosed with kakkonto-induced pneumonitis. Kakkonto was discontinued, and systemic corticosteroid therapy was initiated, resulting in rapid improvement. The peripheral blood drug-induced lymphocyte stimulation test was positive for kakkonto. Because the clinical and radiological findings of JHM-induced pneumonitis are nonspecific, careful medication history-taking, particularly for JHM, is essential for diagnosing unexplained pneumonitis.