Fadi Abualhommos, Rahaf Fetyani, Yasmeen Butt, Michael Gotway, Abeer Almajali, Jehad Azar
Hot tub lung (HTL) is a rare granulomatous pneumonitis caused by inhalational exposure to Mycobacterium avium complex (MAC)-contaminated hot tub water, with debated pathogenesis encompassing both hypersensitivity and infectious mechanisms. A 66-year-old woman with progressive exertional dyspnea was initially misdiagnosed with non-fibrotic hypersensitivity pneumonitis attributed to pheasant exposure and treated with corticosteroids and mycophenolate without improvement. High-resolution CT demonstrated diffuse centrilobular nodules with air-trapping. Surgical lung biopsy revealed bronchiolocentric non-necrotizing granulomas with rare MAC organisms despite negative bronchoalveolar lavage cultures. Detailed clinical history disclosed daily indoor hot tub use coinciding with symptom onset. Following hot tub cessation and initiation of azithromycin, ethambutol and rifabutin, she ultimately achieved complete clinical and radiologic resolution. HTL represents a heterogeneous spectrum from immune-mediated hypersensitivity to true mycobacterial infection. Persistent interstitial lung disease despite ongoing immunosuppression should prompt a thorough hot tub exposure history and selected patients may require antimycobacterial therapy alongside exposure cessation.