Spinocerebellar Ataxia 2 (SCA2)

Inheritance
Autosomal dominant, with anticipation.

Molecular genetics and pathogenesis
SCA 2 is due to an expanded CAG repeat in a coding region of the SCA2 gene, encoding ataxin-2, a protein of unknown function. Like the other dominant polyglutamine diseases, the toxic effect is believed to be primarily due to a gain of function of the mutated protein, rather than a lost function of the wild-type.

Clinical manifestations
Ataxia of limbs, gait, speech, eye movements; slowed eye movements; exaggerated or diminished reflexes; extrapyramidal signs, including parkinsonism, dystonia, action tremor, and myoclonus; mild cognitive impairment; peripheral neuropathy; REM sleep behavior disorder.

Treatment
Parkinsonism may be responsive to levodopa.

References
OMIM
http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=183090

Geschwind DH, Perlman S, Figueroa CP, Treiman LJ, Pulst SM. The prevalence and wide clinical spectrum of the spinocerebellar ataxia type 2 trinucleotide repeat in patients with autosomal dominant cerebellar ataxia. Am J Hum Genet. 1997 Apr;60(4):842-50. PubMed ID: 9106530

	Spinocerebellar Ataxia 3 (SCA3); Machado-Joseph Disease