Gene dosage influences the age at onset of SCA2 in a family from southern Italy

Spinocerebellar ataxia type 2 (SCA2) is the most common form of autosomal dominant cerebellar ataxia in southern Italy (1). The expansion of a CAG trinucleotide repeat in exon 1 of the SCA2 gene, located on chromosome 12q23-24.1, is responsible for the disease. Normal alleles have 14 to 31 CAG repeats interrupted by one to three CAA trinucleotides, whereas expanded alleles have 33 to over 200 pure repeats, as reported in neonatal cases (2). Clinically, SCA2 is characterized by gait and limb ataxia, dysarthria, slow saccadic eye movements, supranuclear ophthalmoplegia and peripheral neuropathy. Recently, several patients have been described with expansion in the SCA2 gene and an L-dopa responsive parkinsonism