Hypersensitivity pneumonitis reaction to Mycobacterium avium in household water.

BACKGROUND: Hypersensitivity pneumonitis has been described with exposure to aerosolized Mycobacterium avium complex (MAC) in indoor hot tubs (hot tub lung).

OBJECTIVES: To describe a case of MAC-associated hypersensitivity pneumonitis-like reaction possibly from showering and review previous hot tub lung reports.

METHODS: For the case report, we investigated a patient with histologically diagnosed hypersensitivity pneumonitis and MAC-positive sputum culture findings. Mycobacterial cultures were obtained from his home and workplace. Isolates were typed using pulsed-field gel electrophoresis. For the review, MEDLINE and EMBASE were searched for hot tub lung reports, which were reviewed and summarized.

RESULTS: A 50-year-old man had progressive dyspnea and episodic fever and myalgias. Pulmonary function testing results revealed obstruction and impaired diffusion; a chest CT scan found diffuse, centrilobular, ground-glass nodules, and air trapping, and a lymphocytic alveolitis with an elevated CD4/CD8 ratio. Transbronchial biopsy showed multiple well-formed nonnecrotizing granulomas. Multiple respiratory samples and shower and bathtub specimens grew MAC, with matching pulsed-field gel electrophoresis patterns. The patient changed from showering to tub bathing. Prednisone and antimycobacterial drugs were administered for approximately 1 year. His symptoms, pulmonary function abnormalities, and CT scan findings resolved. The literature review yielded 36 cases of hot tub lung. Clinical features included dyspnea (97%), cough (78%), and fever (58%). Pulmonary function testing showed obstruction (67%), restriction (55%), and impaired diffusion (75%). A chest CT scan showed ground-glass opacification (95%) and nodules (67%). Granulomas were well-formed in 95%. Treatments included discontinuation of hot tub use and prednisone, antimycobacterial drugs, or both. Outcomes were favorable.

CONCLUSIONS: A hypersensitivity pneumonitis-like reaction to mycobacteria can occur from exposures other than hot tubs. There are key differences between classic hypersensitivity pneumonitis and MAC-associated hypersensitivity pneumonitis. Antimycobacterial therapy may be required. The possibility of MAC hypersensitivity pneumonitis from showering raises potential implications in the investigation of patients with hypersensitivity pneumonitis.