Diagnosis and management of hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an interstitial lung disease that occurs in individuals who are genetically susceptible and who have an exaggerated immune reaction to inhaled environmental antigens. Persistent inflammation may lead to the development of lung fibrosis, which adversely affects survival. Diagnostic evaluation includes assessment of exposure history, serologic testing for precipitating antigens, high-resolution computed tomography, bronchoalveolar lavage cellular analysis, and histopathology. Multidisciplinary discussion among expert subspecialists is essential for confirming an accurate diagnosis and for determining the need for a lung biopsy. The primary treatment strategy involves avoidance of the precipitating antigen, which is associated with a mortality benefit. Pharmacotherapy includes corticosteroids, azathioprine, mycophenolate mofetil, and rituximab, although their use is supported by limited evidence. In cases of patients with fibrotic HP, nintedanib and lung transplantation may be considered. Additional research is needed to create validated environmental questionnaires, improve serologic testing for responsible antigens, and optimize timing and duration of effective pharmacological therapies.