Hot tub lung: an occupational hazard

Table 1. Characterisation of a cluster of confirmed, probable and possible cases of hot tub lung related to maintenance work on hot tubs

	Case 1	Case 2	Case 3	Case 4	Case 5
Characteristics
Age yrs	30	47	35	56	64
Sex	Male	Male	Male	Male	Male
Smoking history	Current	Former	Never	Former	Former
Medical history	Healthy	Healthy	Healthy	Psoriasis Asthma OSAS MI	Hypertension
Atopy	-	+	+	+	-
Known immune deficiency	-	-	-	-	-
Duration of maintenance of hot tub filters	6 months	4 months	1 month	8 yrs (sporadic)	8 yrs
Symptoms
Duration months	2	2	0.5	0.5	24
Recurrent influenza-like symptoms	+	+	+	+	+
Symptoms 4–8 h after exposure	+	+	+	+	+
Dyspnoea	+	+	+	-	-
Cough	+	+	+	+	-
Fever	+	+	+	+	+
Weight loss	+	-	-	-	-
First diagnosis	Infection	Embolism	Infection
Clinical investigations
P_O₂ kPa	8.9	7.9
Chest radiography: interstitial opacity	+	+	-	-	-
HRCT: ground-glass opacity, nodular infiltrates	+	+
FVC^# % pred
At diagnosis	92	73	77	114
After recovery	121	102	108	108	95
FEV₁^# % pred
At diagnosis	87	75	89	106
After recovery	111	104	101	109	81
D_L,CO % pred
At diagnosis	76			104
After recovery	90	84	144		91
Lymphocytosis in BAL	+			+
Histopathology with typical granuloma	+
M. avium in BAL culture	+			+	+
M. avium in sputum culture				+

P_O₂: oxygen tension; HRCT: high-resolution computed tomography; FVC: forced vital capacity; % pred: % predicted; FEV₁: forced expiratory volume in 1 s; D_L,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].