A Large Multicenter Cohort of Ataxia–Telangiectasia: Clinical, Immunologic, Genetic, and Survival Outcomes

BACKGROUND: Ataxia telangiectasia (AT) is a life-threatening multisystem disorder characterized mainly by neurologic manifestations, infections, and malignancy. We aimed to present a comprehensive analysis of demographic, clinical, immunologic, and genetic features and outcomes of patients with AT in Iran. METHODS: We conducted a retrospective cohort study of 305 registered patients with AT enrolled through a national referral network (2002-2025). Diagnosis was established according to the European Society for Immunodeficiencies criteria. RESULTS: Mean age at diagnosis and mean age at onset were 72.0 (±46.0) and 25.2 (±35.57) months, respectively. A substantial proportion of patients presented with non-neurological manifestations as their first clinical feature (43.9%). Among non-neurological manifestations, pneumonia was the second most common initial manifestation (13%) and the most frequent infectious complication (30.2%). Variants classified as severe under the predicted loss-of-function (PVS1) criteria were identified in 104 patients, representing 83.8% of those who underwent genetic evaluation. Immunoglobulin abnormalities were detected in 84.7% of patients. A notable proportion of patients showed class switching recombination defects (45.6%), which were associated with a higher burden of clinical morbidity. Median age at death was 12.8 years (95% CI, 11.0-15.0), and the estimated overall survival rates at 5 and 10 years were 81.6% and 60.2%, respectively. Malignancy (28.9%) and respiratory tract infections (20.0%) were the most common causes of death, respectively. CONCLUSION: This large national cohort provides a comprehensive characterization of the clinical, immunologic, and genetic landscape of AT and its determinants of outcome, thereby improving diagnostic recognition, risk stratification, and patient management.