Objective: The primary immunodeficiency syndromes of cytotoxic T lymphocyte-associated protein 4 (CTLA-4) haploinsufficiency and lipopolysaccharide-responsive and beige-like anchor protein (LRBA) deficiency present with multisystem immune dysregulation. The aim of this study was to characterize and compare the pulmonary manifestations of these two diseases. Methods: We retrospectively analyzed the pulmonary clinical, radiologic, and histopathologic characteristics of 6 patients with CTLA-4 haploinsufficiency and 4 patients with LRBA deficiency with pulmonary involvement followed at a large tertiary care center. Results: Chronic respiratory symptoms were more frequent in patients with LRBA deficiency versus CTLA-4 haploinsufficiency (4/4 versus 1/6). Cough was the most common respiratory symptom. Abnormalities in pulmonary exam and pulmonary function testing were more frequent in LRBA deficiency (4/4, 2/4) compared to CTLA-4 haploinsufficiency (1/6, 2/6). Chest CT findings included mediastinal lymphadenopathy (4/4 in LRBA deficiency versus 1/4 in CTLA-4 haploinsufficiency), pulmonary nodules (4/4, 3/4), ground-glass opacification (4/4, 3/4), and bronchiectasis (3/4, 1/4). Lymphocytic inflammation, concentrated bronchovasculocentrically and paraseptally, was observed in all patients who had lung biopsies (N=3 with LRBA deficiency; N=3 with CTLA-4 haploinsufficiency). Granulomas were seen in all patients with CTLA-4 haploinsufficiency and in no patients with LRBA deficiency. Conclusion: Despite phenotypic overlap amongst these diseases, LRBA deficiency demonstrated greater severity of pulmonary disease, indicated by respiratory symptoms, pulmonary exam, and intrathoracic radiologic findings. Lymphocytic inflammation is a key histologic feature of both of these disorders. Pediatric pulmonologists should suspect these disorders in the appropriate clinical, radiological, and pathological context to better diagnose and treat these patients.