[A case of bucillamine-induced interstitial pneumonia].

Bucillamine [N-(2-mercapto-2-methylpropionyl)-L-cysteine] is an anti-rheumatic drug which was developed in Japan. Interstitial pneumonia induced by bucillamine has been reported in two patients with rheumatoid arthritis. In this report, we describe another patient who developed bucillamine-induced interstitial pneumonia. In August 1990, a 53-year-old man was admitted because of fever, dry cough and dyspnea on exertion (DOE). Five months previously, he had noted polyarthritis, and treatment with bucillamine was started in May 1990. His polyarthritis improved about 2.5 months after starting bucillamine, but he developed fever, dry cough, and DOE in August 1990. Chest X-ray on admission showed diffuse acinar and interstitial shadows predominantly in the bilateral upper lung fields. Pulmonary function tests revealed decreased vital capacity and diffusing capacity. Arterial blood gas (ABG) analysis revealed moderate hypoxemia with PaO2 67 Torr. After stopping bucillamine, the fever, dry cough, and DOE improved gradually, and the abnormal shadows on chest X-ray and ABG analysis showed moderate improvements. Bronchoalveolar lavage studies showed that total cell counts and proportion of lymphocytes were increased, and CD4+/CD8+ ratio of T cell subsets was decreased to 0.56. Transbronchial lung biopsy specimen revealed lymphocytic alveolitis and mild interstitial thickening. Lymphocyte stimulation test to bucillamine was negative, but patch test with bucillamine was positive. From the patient's clinical course, laboratory data, and pathologic findings, we concluded that this is a case of bucillamine-induced interstitial pneumonia. After treatment with corticosteroid, his chest X-ray and pulmonary function test showed marked improvements.(ABSTRACT TRUNCATED AT 250 WORDS)