Hot tub lung may mimic refractory pneumonitis

Rare MAC organisms on lung biopsy and an overlooked exposure history shifted the diagnosis after prolonged immunosuppression.

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A 66-year-old woman treated for more than 2 years for presumed hypersensitivity pneumonitis had persistent imaging abnormalities and recurrent hypoxic respiratory failure.
2

A detailed exposure history revealed daily indoor hot tub use beginning in 2020, before the onset of respiratory symptoms.
3

Biopsy showed airway-centered and airspace granulomas, organizing pneumonia, and rare MAC organisms; BAL culture was negative.
4

The findings supported hot tub lung involving hypersensitivity pneumonitis and possible MAC infection, although the hot tub water and filters were not cultured.
5

After hot tub avoidance, immunosuppression taper, and azithromycin, ethambutol, and rifabutin, symptoms improved and imaging resolved approximately 24 months after presentation.

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