Immunodeficiency-Associated Childhood Interstitial Lung Diseases: Data from the Türkiye chILD Registry.

Background: Childhood interstitial lung diseases (chILD) and immunodeficiencies are rare, heterogeneous, and clinically challenging disorders. Aims: To evaluate the clinical and radiological characteristics of immunodeficiency-related chILD using data from the Türkiye chILD Registry (chILD-TR). Study Design: Retrospective cohort study. Methods: Patients registered with the B3 code, according to the chILD-European classification, from 18 participating centers were included. Patients were classified into primary immunodeficiency (PID) and secondary immunodeficiency (SID) groups. Demographic, clinical, and radiological variables were compared between the two groups. Results: Among 667 patients registered in the chILD-TR, 114 (17%) had immunodeficiency-related chILD, including 53 (47%) females. The median current age was 156 months (range: 23-357), the age at symptom onset was 60 months (range: 0-215), and the age at chILD diagnosis was 85 months (range: 2-217). PID was identified in 77 patients (67.6%) and SID in 37 patients (32.4%). The PID group had significantly lower median current age, age at first symptom, and age at chILD diagnosis compared with the SID group ( Conclusion: Immunodeficiency-associated chILD encompasses a heterogeneous spectrum of disorders and is associated with increased mortality. Distinct clinical and radiological patterns were observed between PID and SID. These findings underscore the importance of early detection, individualized diagnostic strategies, and ongoing follow-up to improve outcomes in this high-risk population. Recognition of post-infectious BO and following HSCT is critical for timely intervention.