MAC infection can induce hypersensitivity pneumonitis in patients with exposure to hot tube water

MAC can also induce a hypersensitivity pneumonitis ("hot tub lung"), particularly in those with recent exposure to contaminated hot tub water. This can happen in young healthy patients as well.

Manifestations include an subacute (within hours), flu-like illness with dyspnea, cough, malaise, and fever.  Most cases are self-limited and resolve with close observation, supportive care, and avoidance of hot tub exposure.  However, if symptoms worsen or persist, a short course of prednisone is often indicated.

This differs from Pseudomonas infections associated with hot tub use that present as folliculitis, not pneumonia.  In addition, Pseudomonas pneumonia would be more likely to develop over days (not hours) and be associated with a lobar infiltrate (not patchy interstitial infiltrate).