XRCC1 and Ataxia-telangiectasia: The complexity in diagnosing AOA2 is amplified by its phenotypic similarities to other ataxic disorders featuring oculomotor apraxia, including ataxia oculomotor types 1 and 4 (AOA1, AOA4), XRCC1 (spinocerebellar ataxia, autosomal recessive 26; SCAR26), ataxia-telangiectasia (A-T), and ataxia-telangiectasia-like disorder 1 and 2 (ATLD1, ATLD2).