Introduction: Fibrotic progression in interstitial lung diseases (ILDs) results from complex interactions between host genetics and environmental exposures. Hypersensitivity pneumonitis (HP) is the most prevalent fibrotic ILD in our cohort. However, its diagnosis is often made with low confidence due to its phenotypic overlap with idiopathic pulmonary fibrosis (IPF). Previously, we demonstrated that a mixture of fungal antigens collected from the homes of HP patients elicited a robust T-cell response, supporting its potential use as a complementary diagnostic tool.
Objectives: To comprehensively characterize household mould exposure in patients with pulmonary fibrosis through home inspection and air sampling.
Materials and Methods: Air samples were collected in duplicate from the homes of 55 patients with HP, IPF, and other ILDs in the northern region of Portugal. Indoor and outdoor fungal concentrations were measured and phenotypic identification was performed based on micro- and macroscopic morphological features.
Results: Within our cohort, 29% of homes showed signs of water infiltration, visible mould growth, or wall discoloration. However, 42 patients (76%) had abnormal levels of fungal exposure (airborne fungal concentration >500 CFU/m³, higher indoor than outdoor concentrations, or toxigenic species concentrations >12 CFU/m³), reflecting suboptimal living conditions. Cladosporium spp. and Penicillium spp. were the most prevalent genera across all ILD diagnoses. Although not the most prevalent genus, Rhodotorula spp. was significantly more frequent in the homes of IPF patients. The toxigenic species Aspergillus fumigatus and Aspergillus niger were found at higher concentrations indoors than outdoors. Patients with IPF were exposed to higher concentrations of mould spores compared to those with HP, as well as to higher levels of toxigenic species.
Conclusions: There is an underrecognized household mould exposure particularly in IPF patients. Differences in the frequency of specific fungal species isolated from fibrotic HP and IPF patients’ dwellings, may correlate with diverse clinical manifestations and prognosis.