Hypersensitivity pneumonitis- single center data from Hungary

<bold>Introduction:</bold> Differentiating hypersensitivity pneumonitis (HP) from other interstitial lung diseases (ILD) can be challenging due to often unidentified inciting agents. Currently there are no comprehensive data about the Hungarian HP population. <bold>Aim:</bold> We defined the characteristics of HP patients in a large Hungarian ILD center, focusing on factors aiding a definite HP diagnosis. <bold>Methods:</bold> Data from multidisciplinary diagnostic (MDD) team presented cases (2017-2021) were reviewed (n= 964). All suspected HP patients (n = 51, 5.3%) charts were reviewed including symptoms, exposures, lung function, CO diffusion, HRCT pattern and bronchoalveolar lavage (BAL) cell counts. Patients with confirmed definite HP diagnosis (n = 26) were compared to those with alternative diagnoses (n = 25). <bold>Results:</bold> Definite HP patients were mainly women of slightly younger age (73%, 56.9 ± 13.7 years) than the alternative diagnosis group (48%; 58.7 ± 15.1 years). The most common alternative diagnosis was IPF (28%). Leading respiratory symptom was dyspnea in both groups (86% vs.78%), while cough was significantly more often in HP patients (71% vs. 26%, p<0.01). Wood/metal dust exposure was higher in alternative diagnosis group (5% vs. 35%, p=0.012). Both groups had a restrictive ventilatory pattern (FVC=70.9 ± 21.5 % vs. 77.5 ± 18.3%) and decreased CO diffusion (TLCO=66.4 ± 20.2% vs. 62.3 ± 25.9%). HRCT pattern was mainly mosaic attenuation and ground glass opacities in both groups. BAL lymphocyte count over 30% was noted in 47% of definite HP cases (vs. 22%). <bold>Conclusion:</bold> Our study describes the clinical features of Hungarian HP patients, underscoring diagnostic challenges and the necessity of a multidisciplinary approach.