Pulmonary Nocardiosis due to Nocardia asiatica in a Patient with ANCA-associated Vasculitis

Nocardia asiatica is a rare causative organism responsible for opportunistic infection, and was first reported by Kageyama et al. in 2004. We report herein on a very rare case of N. asiatica infection in a 76-year old male patient with ANCA-associated vasculitis and a history of pulmonary tuberculosis. The patient developed pulmonary nocardiosis due to N. asiatica while receiving glucocorticoid therapy. Chest computed tomography demonstrated multiple granules and cavity formation mainly in the left lower lobe. From the images, we suspected opportunistic infection, possibly pulmonary tuberculosis or pulmonary damage due to ANCA-associated vasculitis. Nocardia sp. was detected from a bronchoalveolar lavage culture and N. asiatica was identified by 16S ribosomal DNA gene sequencing. Cranial magnetic resonance imaging revealed no abnormality. Administration of Doripenem (1.5g/day) and sulfamethoxazole-trimethoprim (4g/day) was started, and the patient's clinical and imaging findings promptly improved. Thereafter, he received sulfamethoxazole-trimethoprim (2g/day) and prednisolone (10 mg/day) as maintenance therapy for ANCA-associated vasculitis for more than one year, and there has since been no recurrence of the Nocardia infection.