Spinocerebellar ataxia type 2 (SCA2) is characterized by progressive muscle weakness including trouble walking, and eye muscle problems. Symptoms usually appear in the 40's and then progress. Genetic testing is diagnostic and used to detect an abnormal CAG trinucleotide repeat expansion of the ATXN2 gene. SCA2 is inherited in an autosomal dominant manner so children of an affected individual have a 50% chance of inheriting the condition.