Objective: To evaluate the characteristics of the patients who were followed-up with the diagnosis of ataxia telangiectasia (AT) and to assess the relationship between the hyper IgM (HIGM) phenotype and their prognosis.

Materials and Methods: From 2007 to 2019, the study included 68 patients aged 3-35 years who were followed-up with the diagnosis of AT. We retrospectively evaluated the clinical and immunological characteristics and follow-up results.

Results: There were 36 girls and 32 boys with a median follow-up of 10 years (1-12 years). The most common complaints upon admission were unsteady walk in 87%, infection in 6%, presence of a family history in 6%, and intracranial mass in 1%. The marriage was consanguineous in 85% of the parents. Ataxia was seen in 100% of the patients, telangiectasia in 97%, and immune deficiency in 88%. Bronchiectasis was observed in 23.5% of the patients, chronic diarrhea in 19%, lymphoproliferation in 15%, malignancy in 10%, autoimmunity in 10%, liver failure in 6%, and granulomatous skin lesions in 6%. Thirteen patients (19%) died during follow-up. The HIGM phenotype was identified in 31% of the patients. Recurrent upper and lower respiratory tract infections (p=0.004 and p<0.0001, respectively), liver failure (p=0.005), and autoimmune diseases (p=0.023) were significantly higher in the HIGM (+) group than the HIGM (-) group. Life expectancy was shorter in the HIGM (+) group with 14 ± 0.73 years (CI 95% 12.55-15.44) compared to the HIGM (-) group with 18 ± 1.64 years (CI 95% 14.77-21.22) (p=0.054).

Conclusion: During the early childhood period and before the characteristic findings of AT develop, the patients might present at a hospital with infections, autoimmunity, lymphoproliferation, or malignancy. Physical examination, high alpha-fetoprotein (AFP) levels and immunological testing provide important data for the correct diagnosis. The HIGM phenotype aggravates the clinical course of the disease resulting in fatalities at an earlier age and at a higher rate.