PT - JOURNAL ARTICLE AU - Mark Hamblin AU - Helmut Prosch AU - Martina Vašáková TI - Diagnosis, course and management of hypersensitivity pneumonitis AID - 10.1183/16000617.0169-2021 DP - 2022 Mar 31 TA - European Respiratory Review PG - 210169 VI - 31 IP - 163 4099 - http://err.ersjournals.com/content/31/163/210169.short 4100 - http://err.ersjournals.com/content/31/163/210169.full SO - EUROPEAN RESPIRATORY REVIEW2022 Mar 31; 31 AB - Hypersensitivity pneumonitis (HP) is a complex and heterogeneous interstitial lung disease (ILD) that occurs when susceptible individuals develop an exaggerated immune response to an inhaled antigen. In this review, we discuss the latest guidelines for the diagnostic evaluation of patients with suspected HP, the importance of identifying patients with fibrotic and progressive disease, and the evidence supporting the drugs commonly used in the treatment of HP. Differential diagnosis of HP can be challenging and requires a thorough exposure history, multidisciplinary discussion of clinical and radiologic data, and, in some cases, assessment of bronchoalveolar lavage lymphocytosis and histopathologic findings. Patients with HP may be categorised as having non-fibrotic or fibrotic HP. The presence of fibrosis is associated with worse outcomes. A proportion of patients with fibrotic HP develop a progressive phenotype, characterised by worsening fibrosis, decline in lung function and early mortality. There are no established guidelines for the treatment of HP. Antigen avoidance should be implemented wherever possible. Immunosuppressants are commonly used in patients with HP but have not been shown to slow the worsening of fibrotic disease. Nintedanib, a tyrosine kinase inhibitor, has been approved by the US Food and Drug Administration for slowing the progression of chronic fibrosing ILDs with a progressive phenotype, including progressive fibrotic HP. Non-pharmacological interventions, such as oxygen therapy, pulmonary rehabilitation and supportive care, may be important components of the overall care of patients with progressive HP.Guideline statements for the diagnosis of hypersensitivity pneumonitis have recently been published by the ATS/JRS/ALAT and CHEST. This review examines differences in the two guideline statements and discusses current management options. https://bit.ly/3o6uJh2