Waterproofing spray-associated pneumonitis: review of 29 cases and comparisons with acute eosinophilic pneumonia and hypersensitivity pneumonitis

Purpose: Waterproofing spray-associated pneumonitis (WAP) proceeds to acute respiratory failure and is characterized by diffuse bilateral ground-glass opacities on computed tomography. These features are similar to those of acute eosinophilic pneumonia (AEP) and hypersensitivity pneumonitis (HP). This study identified the characteristics of WAP and compared them with those of AEP and HP. Methods: We conducted a retrospective study of adult patients with WAP, AEP, and HP in Fukujuji Hospital from 1990 to 2018. Furthermore, data from patients with WAP were collected from publications in PubMed and the Japan Medical Abstracts Society and combined with data from our patients. Results: Twenty-nine patients with WAP, eleven patients with AEP, and thirty patients with HP were reviewed. There were no significant differences between the characteristics of WAP and AEP patients, such as age, sex, smoking habit, and laboratory findings. The features of WAP and HP were significantly different. The duration from symptom appearance to hospital visit was shorter in patients with WAP (median 1 day) than in patients with AEP (median 3 days, p =0.003) and HP (median 30 days, p <0.001). The dominant cells in the bronchoalveolar lavage fluid of patients with WAP, AEP, and HP were different (respectively macrophages, eosinophils, and lymphocytes). Conclusions: It was easy to distinguish between WAP and HP because there were many different features. However, the features of WAP and AEP were similar, making differentiation between those two diseases difficult. To distinguish among WAP, AEP and HP, the speed of disease progression and a bronchoscopic examination are very important.