Abstract Introduction Interstitial lung diseases (ILD) represent a heterogeneous group of disorders characterized by inflammation and fibrosis of the pulmonary interstitium. They may arise idiopathically, accompany connective-tissue disease, or be triggered by environmental exposures. One lesser-known exposure-related subtype is “hot tub lung,” a presumed form of hypersensitivity pneumonitis caused by inhalation of aerosolized water contaminated by non-tuberculous mycobacteria. Case Presentation A 40-year-old healthy male developed gradual progressive exertional dyspnea and reduced exercise capacity over a two-year period. He denied cough, wheeze, chest pain, fever, weight loss, rash or arthralgias. Had brief smoking history (two years); denied occupational or environmental exposures other than frequent sauna use. Family history was non-contributory. On examination, air entry was good and no adventitious lung sounds were noted. An incidental CT scan performed for abdominal pain revealed peripheral ground-glass opacities, reticular alveolar consolidations at the lung bases, mild parenchymal distortion and traction bronchiectasis. A dedicated high-resolution chest CT (HRCT) was interpreted as demonstrating a classic nonspecific interstitial pneumonia (NSIP) pattern. Pulmonary function testing showed a restrictive pattern, markedly reduced diffusing capacity. Rheumatologic screening revealed weakly positive ANA U1 small-nuclear ribonucleoprotein (34, normal 11); the remainder of the connective-tissue disease panel was unremarkable. Because of diagnostic uncertainty a surgical lung wedge resection was performed: pathology revealed patchy interstitial fibrosis with fibroblast foci and relatively preserved adjacent lung parenchyma — features consistent with a usual interstitial pneumonia (UIP) pattern. With connective-tissue disease deemed unlikely, a diagnosis of probable “hot tub lung” in the setting of frequent sauna exposure was made. Following cessation of sauna exposure, repeat HRCT and PFTs demonstrated stable disease. Discussion Hot tub lung is regarded as a distinct form of (HP) triggered by aerosolized warm-water exposures (eg, spas, hot tubs, showers). A key diagnostic clue is a meticulous and detailed exposure history: including frequency, duration, setting (indoor vs outdoor), ventilation and water system maintenance, onset of symptoms relative to exposure. Radiographic findings may include ground-glass opacities, centrilobular nodules and reticular changes. Although non-tuberculous mycobacteria are often isolated, the underlying mechanism is believed to be immune-mediated rather than a straightforward infection. The principal therapeutic step is avoidance of the implicated exposure; corticosteroids may be considered for advanced or symptomatic disease. Clinicians evaluating ILD should maintain a high index of suspicion for hot tub lung, systematically include detailed water-aerosol exposure screening in history, and refer to multidisciplinary ILD review when the diagnosis remains uncertain. This abstract is funded by: None
Hasan et al. (Fri,) studied this question.