Diffuse pulmonary disease caused by nontuberculous mycobacteria in immunocompetent people (hot tub lung)

The clinicopathologic spectrum of infections due to nontuberculous mycobact eria (NTM) includes cavitary disease, opportunistic infection, and nodular disease associated with bronchiectasis. We report a less well-described man ifestation of NTM infection: 10 immunocompetent patients without preexistin g bronchiectasis had radiographic evidence of diffuse infiltrative lung dis ease. The most common symptoms were dyspnea, cough, hypoxia, and fever. All 10 patients had used a hot tub. Histologic examination revealed exuberant nonnecrotizing, frequently bronchiolocentric, granulomatous inflammation in all cases. In 1 case, necrotizing granulomas were also noted. The inflamma tion often was associated with patchy chronic interstitial pneumonia and or ganization. Cultures revealed NTM in all cases (Mycobacterium avium complex in all but 1 case), but staining for acid-fast bacilli as positive in only 1 case. Four patients received corticosteroids alone for presumed hypersen sitivity pneumonia, 4 were treated with antimycobacterial therapy, and 2 re ceived both. All patients demonstrated significant improvement at the time of follow-up. These findings suggest that disease due to NTM may manifest a s diffuse infiltrates in immunocompetent adults and that hot tub use may be an important risk factor for this disease pattern.