Pulmonary Mycobacterium abscessus disease in a patient receiving low-dose methotrexate for treatment of early rheumatoid arthritis

A 70-year-old woman with methotrexate (MTX)-refractory rheumatoid arthritis (RA) was referred to our hospital for introduction of biological therapy. On high-resolution computed tomography scans, the patient exhibited abnormal findings such as bronchiectasis and centrilobular small nodules, which were highly suggestive of pulmonary nontuberculous mycobacterial (NTM) disease. Although mycobacterial cultures of sputum specimens yielded negative results, cultures of bronchoalveolar lavage fluids grew Mycobacterium abscessus. Frequent follow-up chest radiographs indicated that the patient's pulmonary disease became rapidly worse in 1 month following dose escalation of MTX and administration of lowdose prednisolone. Oral clarithromycin and levofloxacin, chosen on the basis of in vitro susceptibility testing, led to a dramatic recovery from this potentially life-threatening complication. Through our experience with this case, we have learned that (1) pulmonary M. abscessus disease can progress rapidly, even during nonbiological anti-RA therapy; (2) regular follow-up chest radiographs are useful to ensure timely implementation of anti-NTM treatment; (3) bronchoscopic testing should be considered when patients are suspected of pulmonary NTM disease but do not meet the diagnostic criteria; and (4) early isolation, identification, and susceptibility testing of causative NTM species are critical for favorable outcomes.