Dual pathology, dual burden: Functional impact of emphysema and fibrosis in Hypersensitivity Pneumonitis

Hypersensitivity pneumonitis (HP) is a complex interstitial lung disease with heterogeneous presentations. In some patients, radiological coexistence of emphysema and fibrosis creates a distinct functional phenotype that complicates disease progression and management. To evaluate the functional impact of combined emphysema and fibrosis in HP patients and to identify clinical predictors associated with this dual pathology.

We retrospectively analyzed 215 patients diagnosed with HP between 2010 and 2023. Demographic data, exposure history, radiological findings (HRCT), and pulmonary function parameters (FVC, DLCO, FEV₁) were collected. Patients were classified into three groups: fibrotic HP, non-fibrotic HP, and combined emphysema with fibrosis (CE-HP). Statistical analyses were performed using SPSS v22.0.

Of the 215 patients, 68 (31.6%) had fibrotic HP and 42 (19.5%) presented with CE-HP. Patients with CE-HP were significantly older (mean 66.2 ± 9.1 years) and more often male and smokers (p < 0.05). FVC and DLCO values were lower in CE-HP compared with non-fibrotic and fibrotic groups. A moderate negative correlation was found between extent of emphysema and DLCO (r = -0.56, p < 0.001). In multivariate analysis, age > 65 years, male gender, and smoking history were independent predictors of CE-HP development.

The coexistence of emphysema and fibrosis in HP represents a distinct clinical phenotype with significant functional impairment. Recognition of this dual pathology is crucial for accurate prognostication and individualized management strategies.