Evaluate the Neurological Effects of EryDex on Subjects With A-T

Inclusion Criteria: * Clinical diagnosis of A-T * In autonomous gait or is helped by periodic use of a support * Genetic confirmation of A-T * Body weight ≥15 kg Exclusion Criteria: * Participation in another clinical study * Immune impairment * History of severe impairment of the immunological system * Current neoplastic disease or previous neoplastic disease not in remission for at least 2 years * Severe or unstable pulmonary disease * Uncontrolled diabetes * Current chronic or acute significant renal and/or hepatic impairment * Any previous oral or parenteral steroid use within 6 weeks before Baseline. Treatment with inhaled or intranasal steroids for asthma or allergies, as well as use of topical steroids will be permitted * A disability that may prevent the subject from completing all study requirements