SCA-2 is an autosomal dominant inherited disorder characterized by ataxia,
slow saccades, and hyporeflexia. The authors evaluated a patient with a mil
d balance problem with a SCA-2 allele sized at 33 CAG repeats. The authors
then ascertained her 91 year-old mother, who showed disease onset at age 86
with an SCA-2 allele of identical size. Their study indicates that 33 CAG
repeats can be pathogenic at the SCA-2 locus, though such an allele may pro
duce an extremely late onset and gradual rate of disease progression.