Inclusion Criteria:  Have a confirmed diagnosis of A-T.  a) Patients will either have a prior molecular confirmation or will be investigated;  If female and of childbearing potential, must be using an effective birth-control method with a history of reliability for the individual patient; If a female with a male partner. If the male is of childbearing potential, adequate methods of contraception must be employed including use of condoms with spermicide. No sperm donation for 90 days until after the conclusion of the study; Body weight > 15 kg; Be able to participate for the full term of the clinical investigation; The patient and his/her parent/caregiver (if below the age of consent), or a legal representative, has provided written informed consent to participate. If consent is provided solely by the caregiver in accordance with local regulations, the patient must provide assent to participate in the study  Exclusion Criteria:  Females that are  a) pregnant, or are breast-feeding;  Females of childbearing potential who do not use adequate birth control, as determined by their Health Care Provider; Patients with severe vision or hearing impairment (that is not corrected by glasses or hearing aids) that, at the investigator's discretion, interferes with their ability to perform study assessments; Patients who have been diagnosed with arthritis or other musculoskeletal disorders affecting joints, muscles, ligaments, and/or nerves that by themselves affects patient's mobility and, at the investigator's discretion, interferes with their ability to perform study assessments; A disability that may prevent the patient from completing all study requirements; Severe or unstable pulmonary disease; Uncontrolled diabetes. Patients with diabetes that has been stabilized (i.e. no hypoglycemic or hyperglycemic episodes in the past 3 months) will be eligible; Current neoplastic disease or previous neoplastic disease not in remission for at least 2 years; Has participated in any other trial with an investigational drug and received a dose within 30 days; Requires any concomitant medication prohibited by the protocol; Any other severe, unstable, or serious disease or condition that in the Investigator's opinion would put the patient at risk for imminent life-threatening morbidity, need for hospitalization, or mortality; and Evidence of significant medical illness, or psychiatric illness/social situation that would, in the investigator's judgment, make the patient inappropriate for this study.