Home environmental fungal exposure in patients with Hypersensitivity Pneumonitis

<bold>Introduction:</bold> Mold exposure can be a significant factor in the immunopathogenesis of patients with Hypersensitivity Pneumonitis (HP), thus evaluating exposure in the home environment could offer valuable insights into the mechanisms underlying the disease. <bold>Aims:</bold> To evaluate the mycological exposure in the home environment of patients with HP. <bold>Methods:</bold> A thorough home environment evaluation of patients with a HP diagnosis was performed, including collection of air samples using a single-stage microbiologic air impactor. Upon incubation, fungal colony quantification and microscopic identification were performed. <bold>Results:</bold> Thiry-five patients were included, median age 71 years (32-83), 19 (54.3%) were male. Most patients had fibrotic HP (n=27; 77.1%). A total of 75% of the patients exhibited exposure to potentially hazardous levels of fungus. The air samples revealed 17 distinct fungal species, with Cladosporium and Penicillium spp being the most predominant. While 37.4% of patients self-reported signs of fungal exposure, the investigator's visual assessment identified such indicators in 65.7%. All patients who experienced a significant decline in DLCO or FVC had a history of hazardous fungal exposure. Furthermore, elevated indoor exposure to Aureobasidium pullulans was associated with a decline in FVC over an 18-month follow-up period (72.7 vs 31.6%, p = 0.029). Additionally, a higher concentration of Penicillium spp indoors showed a tendency to be associated with a decrease in DLCO. <bold>Conclusion:</bold> Patients with HP are exposed to high levels of fungal antigens. A professional home environmental evaluation is superior to standard outpatient clinic questionnaire in identifying patients’ exposure.