Immunomodulatory Therapies in Hypersensitivity Pneumonitis: A Comprehensive Review

Hypersensitivity pneumonitis (HP) is an immune-mediated interstitial lung disease (ILD) caused by repeated inhalation of environmental antigens. Clinically, it varies widely from temporary, reversible inflammation to long-term, progressive fibrosis. The primary approach in managing HP remains identifying and removing exposure to the causative antigens, and treatment often requires corticosteroids in acute or severe cases. However, many patients, especially those with chronic or fibrotic HP (cHP/fHP), may progress despite corticosteroid treatment, highlighting the urgent need for other effective and tolerable immunomodulatory and antifibrotic therapies. This review discusses the current and emerging treatments for HP, focusing on the rationale, clinical data, and practical aspects of traditional immunosuppressants such as corticosteroids, mycophenolate mofetil, and azathioprine, as well as new biologics and antifibrotic drugs that are transforming the treatment landscape for this complex disease.