Biomarkers and genetic predictors of hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is an inflammatory immune-mediated interstitial lung disease that develops in response to repeated inhalation exposures to various low molecular weight compounds in susceptible individuals. The current guidelines distinguish non-fibrotic and fibrotic phenotypes of HP, with fibrotic HP associated with progression and worse prognosis. The differential diagnosis of HP can be complex and requires careful historytaking, multidisciplinary discussion of clinical and radiological findings, evaluation of lymphocytosis in bronchoalveolar lavage (BAL), and histopathological examination. Differentiating HP from other interstitial lung diseases (ILDs), including fibrotic HP from idiopathic pulmonary fibrosis (IPF), can be difficult, as the clinical, radiological, and histopathological features of HP are highly variable and similar to those of other ILDs. The aim of this review is to systematize the available evidence on predictors of HP for the use in diagnosis. Conclusion. Making the diagnosis is crucial for selecting treatment strategies and prognosis. Indicators such as genetic predictors, serum biomarkers, and BAL can be used to diagnose HP, predict its development and course. Several biomarkers, such as BAL lymphocytosis and specific IgG – precipitating antibodies, are already widely used in clinical practice. Other indicators are still under investigation and may be implemented in the routine patient evaluation in the future.