Abstract Introduction Nontuberculous Mycobacterial (NTM) Infections are environmentally acquired, with person-to-person transmission being rare. The most common presentation is pulmonary disease with chronic respiratory symptoms such as cough, fatigue, sputum production, and weight loss. Mycobacterium avium complex (MAC) and Mycobacterium abscessus are among the most common NTM isolates. Case Description A 71-year-old female from the Southeastern United States with chronic cough and fatigue, on a multi-drug regimen of azithromycin, ethambutol, and rifampin for over two years for a MAC infection continued to grow acid-fast bacilli (AFB) in sputum. Cultures grew Mycobacterium abscessus sensitive to amikacin. CT chest scans demonstrated progressive reticulonodular opacities, worsening bronchiectasis, and multiple sub-centimeter pulmonary nodules. Bronchoalveolar lavage (BAL) was positive for M. abscessus. She was treated with IV amikacin, IV tigecycline, and IV imipenem while continuing oral azithromycin. Rifabutin and ethambutol were discontinued given MAC clearance. Immunologic testing revealed lymphocytopenia. On detailed exposure history, the patient revealed a decade-long routine use of a therapeutic hot tub. After treatment, follow-up CT chest demonstrated decreased conspicuity of pulmonary nodules and unchanged bibasilar reticulation. Discussion Hot tubs are known sources of NTM. Exposure can lead to “hot tub lung”, a hypersensitivity pneumonitis caused by an immune reaction to aerosolized NTM, with actual infections being rare but documented. In this case, the patient’s repeated positive cultures and radiologic evidence of nodular-bronchiectatic disease, and improvement in symptoms in response to treatment all point towards an actual infection rather than immunologic pneumonitis. This case demonstrates recurrent NTM pulmonary disease with sequential infection by two distinct species—M. avium and M. abscessus— possibly acquired from a known source (a hot tub) in the setting of lymphocytopenia, suggesting an underlying immunovulnerability predisposing the patient to reinfection. This patient also resides in the Southeastern region of the United States, which has the highest prevalence of M. abscessus in the country. It highlights the importance of distinguishing hypersensitivity from active infection, particularly in individuals who frequently use communal hydrotherapy pools. It also emphasizes the need for detailed exposure history, microbiologic confirmation, and immunologic evaluation in recurrent NTM disease. The case also underscores the need to address patient education, as ongoing environmental exposure is a key risk factor for reinfection and recurrence. It is important to note that residual nodular or bronchiectatic changes post-therapy usually indicate structural sequelae rather than persistent infection; however, longitudinal follow-up is recommended. This abstract is funded by: None
Archila et al. (Fri,) studied this question.