[Hot tub lung: A retrospective analysis of 14 cases]

Introduction: Hot tub lung (HTL) is a hypersensitivity pneumonitis (HP) related to inhalation of non-tuberculous mycobacteria (NTM) when exposed to ejected jet droplets from a jacuzzi. The aetiological debate is not completely settled in the literature.

Method: An observational study of 14 cases of HTL, diagnosed at the University Hospital of Besançon, France, between 2004 and 2018 according to the diagnostic criteria used in the clinic.

Results: This cohort corresponds to type I HP (inflammatory), with one case of type II HP. Decrease of lung transfer for carbon monoxide was present in 86% of examinations (n=12/14). In total, 84% of bronchoalveolar lavages showed a lymphocytic cellular pattern≥30% (n=11/13). The environmental survey enabled the identification of NTM in 93% of cases (n=13/14), mainly Mycobacterium avium. Serum precipitins directed against NTM were found in 10% of the cases (n=2/20). Three cases received corticosteroid therapy and none received antibiotics. Antigenic eviction has improved the symptomatology in all cases.

Conclusions: Our cohort supports the hypothesis that HTL is predominantly a type I HP. Avoidance of the agent involved (NTM) is necessary. The diagnosis is difficult because serum precipitins against NTM are not easily demonstrable. An environmental survey could facilitate the identification of the NTM. Prevention of HTL depends on education of the clinician and the patient.