Spinocerebellar ataxia type 2

Spinocerebellar ataxia type 2, often shortened to SCA2, is a rare autosomal dominant disorder caused by an expansion of a CAG trinucleotide repeat in the ATXN2 gene. It usually begins around the age of 40. Symptoms include difficulty articulating speech, dysmetria, ataxia, supranuclear ophthalmoplegia with slow saccadic eye movements, and peripheral neuropathy with reduced vibration sense and reduced or absent ankle and knee reflexes. Perioral spasm, head tremor and cramps are also common, and about a quarter of patients show pyramidal signs such as a Babinski sign and increased muscle tone. Average life expectancy is given as 11 years. The disorder is common in India and Cuba, especially in the Cuban province of Holguin, where incidence is about 4 in every 10,000 people.