Machine operator's lung: hypersensitive pneumonitis with a favourable prognosis?

In the last decades, metalworking fluids have become an important cause of occupational hypersensitivity pneumonitis. This study aimed to analyse the clinical features and severity of this occupational disease and compare our findings with hypersensitivity pneumonitis caused by other aetiologies, as conflicting data about patient prognosis has been reported. We found that patients with metalworking-fluids-related hypersensitivity pneumonitis exhibited less lung function impairment and a lower occurrence of fibrosis than hypersensitivity pneumonitis from other causes.

Currently, cases of occupational hypersensitivity pneumonitis (HP) induced by metalworking fluids (MWFs), also called machine operator's lung, are increasing. However, the prognosis for this type of HP is unknown.

We analysed the clinical features and severity of MWF-related HP and compared them with the features of HP resulting from other aetiologies.

Patients with a primary diagnosis of HP who underwent a lung biopsy between 2017 and 2020 were identified from the database of the National Institute of Tuberculosis, Respiratory Diseases, and Thoracic Surgery, Vyšné Hágy, Slovak Republic. The patients were divided into two groups: those with MWF-induced HP (n = 14) and those with HP derived from other aetiologies, including cryptogenic HP (n = 21). We compared patient demographics, lung functioning, bronchoalveolar lavage (BAL) fluid results, computed tomography imaging, and histological results between the two groups.

Patients with MWF HP were characterized by significantly higher forced vital capacity and total lung capacity (P < 0.05) and significantly higher median lymphocyte counts from BAL (P < 0.001). There was also a suggestion that the MWF HP group had higher blood oxygen tension and oxygen saturation with less frequent evidence of fibrotic HP than non-MWF HP patients (36% versus 67%), although these findings were not statistically significant.

MWF-related HP has a better prognosis than HP from other aetiologies. Early removal of patients from exposure and minimizing inhalable levels of MWFs in the workplace are essential for successfully managing patients with MWF-related HP.