Hypersensitivity Pneumonitis With and Without Autoimmune Features: A Clinical Comparative Analysis

Background Hypersensitivity pneumonitis (HP) is an interstitial lung disease (ILD) caused by an immunological reaction to repeated inhalational exposure to antigens. The etiology and exact immunopathology are poorly understood. Autoimmunity overlapping with HP has been described but the role of concomitant autoimmunity in the clinical course and outcome of the HP is not clearly established. In this study, we examined patients diagnosed with HP and compare them to patients with concomitant HP and autoimmunity. Methods Patients were retrospectively screened from a single-center ILD registry. Patients > 18 years with an established multidisciplinary diagnosis of HP were included in the study. Patients with HP without autoimmune features and patients with HP with autoimmune features (HPAF) were assessed. We compared the demographics, clinical characteristics, treatment, and outcomes between the two groups. We used a Cox proportional hazards model to compare lung transplant-free survival outcomes of patients with HPAF to those with non-HPAF HP patients. Results Of 73 patients with HP, 43 were diagnosed with HPAF. Patients with HPAF had a higher echocardiographic probability of pulmonary hypertension as compared to non-HPAF HP patients [48.8 vs 23.3%, p = 0.028, Crude odds ratio (cOR) = 3.14]. Symptomatically, those with HPAF reported a higher prevalence of arthritis as compared to non-HPAF HP (20.9 vs 3.3%, p = 0.040, cOR = 7.68). No significant differences between pulmonary function tests, oxygen requirements, mortality, and lung transplantation rates were found between the two groups. There was no statistically significant difference in transplant-free survival ( p = 0.836). Conclusion Patients with HPAF had a higher echocardiographic probability of pulmonary hypertension as compared to patients with non-HPAF HP. The clinical characteristics and outcomes did not differ between the two groups and concomitant autoimmunity among the HP group did not portend a poorer prognosis.