 1. Patients aged 6-18 years with diagnosed with ataxia, preferably AT will be included. The diagnosis of AT will be made based on the criteria: typical clinical picture plus one of the following: 1. a proven mutation in the ATM gene 2. Deficient ATM protein proven by Western blotting 3. Elevated α-fetoprotein, cerebellar atrophy on MRI and immune deficiency chromosomal breakage T- cell lymphoreticular malignancy. 