Importance of early detection and treatment of occupational hypersensitivity pneumonitis.

Recently, the incidence of pneumoconiosis has decreased due to strict dust control measures and environmental improvements in the workplace. The significance of other occupational diseases has relatively increased. Occupational hypersensitivity pneumonitis (OHP) is mainly caused by allergic reactions to antigens in the workplace. Therefore, the presence of subtle amounts of harmful substances in the environment can increase the risk of developing OHP. Not only organic substances but also inorganic substances can cause OHP. OHP is caused by a specific antibody reaction (type III allergy) or sensitized lymphocytes (type IV allergy) to a specific antigen. Based on the clinical course, OHP is classified into acute and chronic hypersensitivity pneumonitis (HP). Acute HP forms granulomas and is classified as a granulomatous lung disease (nonfibrotic HP), whereas chronic HP rarely forms granulomas and progresses to fibrosis (fibrotic HP). Differentiation between chronic HP and idiopathic or collagen vascular disease-related interstitial pneumonia is challenging. Additionally, the genetic background of each patient influences the onset, leading to diverse onset patterns. Antigens and modes of onset are diverse in the workplace. Therefore, diagnosis is difficult, and many patients may be misdiagnosed. Chronic HP with advanced fibrosis due to delayed antigen identification has a poor prognosis. This study aimed to present an overview of the causative antigens, diagnosis, prevention, and treatment of OHP to provide appropriate and timely medical attention.