Clusters of comorbidities in fibrotic hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a type of interstitial lung disease (ILD) with a variable disease course and prognosis ranging from inflammatory and self-limiting to irreversible and progressive pulmonary fibrosis. Comorbidities are common in HP and may have an impact on prognosis. Due to the heterogeneity of HP presentation and progression, the identification of specific phenotypes in relationship to disease course and outcome is essential. The aim of this study was to identify clusters of comorbidities which could represent phenotypes in fibrotic HP and examine their impact on prognosis.

Patients diagnosed with fibrotic HP at a tertiary referral center for ILD were included. Comorbidities were systematically registered and clusters of comorbidities were identified using cluster analyses. Disease progression and survival was estimated for each cluster.

The cohort comprised 211 patients with 53.6% males, mean age 63.0, baseline FVC 72.7%, DLCO 44.1%. Median follow-up time was 1.8 years (IQR 0.7-3.9). Three clusters with distinct comorbidity profiles and clinical characteristics were identified. One cluster dominated by elder male patients with predominantly cardiovascular diseases was associated with more respiratory hospitalizations and a worse prognosis. Differences in pulmonary function or exercise capacity trajectories between clusters were not observed.

Three clusters with distinct comorbidities were identified and could represent phenotypes in fibrotic HP not previously recognized. The worst prognosis was observed in a cluster dominated by elder males with cardiovascular diseases. Increased focus on prevention and treatment of comorbidities could potentially improve the prognosis of patients with fibrotic HP.