Effects of Vitamin B3 in Patients With Ataxia Telangiectasia

Inclusion Criteria: * A-T patients who visit our outpatient clinic. * Genetically confirmed diagnosis of A-T by the identification of pathogenic mutations of the ATM gene. * Age ≥ 2 years or older and bodyweight ≥ 12 Kg. * Informed consent. Exclusion Criteria: * Additional medical condition or illness that impair the patient's ability to participate in the study (e.g. actual treatment of a malignancy, active infection, poorly controlled diabetes mellitus, hypertension, organ failure, clinically significant hematological or biochemical abnormalities different from the usual abnormalities in A-T) * Elevated serum transaminases (\> 2 times upper limit of normal) * Participation in another interventional study at start of the study or during the study * Pregnancy. * Breast feeding.