Table 1. Characterisation of a cluster of confirmed, probable and possible cases of hot tub lung related to maintenance work on hot tubs
Case 1Case 2Case 3Case 4Case 5
    Age yrs3047355664
    Smoking historyCurrentFormerNeverFormerFormer
    Medical historyHealthyHealthyHealthyPsoriasis
Asthma OSAS
    Known immune deficiency-----
    Duration of maintenance of hot tub filters6 months4 months1 month8 yrs (sporadic)8 yrs
    Duration months220.50.524
    Recurrent influenza-like symptoms+++++
    Symptoms 4–8 h after exposure+++++
    Weight loss+----
First diagnosisInfectionEmbolismInfection
Clinical investigations
    PO2 kPa8.97.9
    Chest radiography: interstitial opacity++---
    HRCT: ground-glass opacity, nodular infiltrates++
    FVC# % pred
        At diagnosis927377114
        After recovery12110210810895
    FEV1# % pred
        At diagnosis877589106
        After recovery11110410110981
    DL,CO % pred
        At diagnosis76104
        After recovery908414491
    Lymphocytosis in BAL++
    Histopathology with typical granuloma+
    M. avium in BAL culture+++
    M. avium in sputum culture+
  • PO2: oxygen tension; HRCT: high-resolution computed tomography; FVC: forced vital capacity; % pred: % predicted; FEV1: forced expiratory volume in 1 s; DL,CO: diffusing capacity of the lung for carbon monoxide; BAL: bronchoalveolar lavage; M. avium: Mycobacterium avium; OSAS: obstructive sleep apnoea syndrome; MI: myocardial infarction; +: present; -: absent. #: European Respiratory Society reference values [2].