Unraveling the Complexities of Hypersensitivity Pneumonitis with Autoimmune Features: A Retrospective Analysis

Some hypersensitivity pneumonitis (HP) patients exhibit autoimmune features (HPAF). This study compared outcomes of HPAF and HP without autoimmune features, focusing on progressive pulmonary fibrosis (PPF) and response to immunosuppression.

A retrospective cohort study included HP patients from a single center. HPAF was defined as HP overlapping with autoimmune disease or presenting autoimmune markers/symptoms not fulfilling connective tissue disease criteria. A control HP group without autoimmune features was randomly selected. Demographics, autoimmune profiles, and outcomes over two years were analyzed.

103 patients were included (52 HPAF; 51 HP). In HPAF, the most common autoimmune diseases were rheumatoid arthritis (9.6%), while 57.7% had isolated autoimmune serology. Groups showed no baseline differences in demographics, exposures, smoking, or lung function. Fibrotic disease on high-resolution CT at diagnosis was less frequent in HPAF (71.2% vs. 88.2%; p = 0.031). At two-year follow-up, survival, transplantation, and PPF prevalence were similar. HPAF patients received immunosuppression less often (69.2% vs. 86.3%; p = 0.038). Among patients under immunosuppression, PPF was significantly lower in HPAF group (8.6% vs. 29.5%; p = 0.021).

Within two years post-diagnosis, HPAF and HP had comparable overall outcomes. However, under immunosuppression, HPAF patients had significantly lower odds of developing PPF (adjusted OR 0.08; 95% CI 0.008-0.816; p = 0.033) compared to HP patients, suggesting a more favorable treatment response.