CTA/CTG expansions at the SCA 8 locus in multiple system atrophy.

OBJECTIVE

Spinocerebellar ataxia type 8 (SCA 8) is an autosomal dominant disorder characterized by cerebellar ataxia with additional features, such as upper motor neuron signs, urinary incontinence and dysphagia. From a clinical standpoint, SCA 8 and the cerebellar form of multiple system atrophy (MSA-C) share several common features.

METHODS

We studied the presence of expanded SCA 8 alleles in 10 sporadic patients with probable MSA-C.

RESULTS

We found 1 patient with a heterozygous CTA/CTG repeat expansion in the pathological range. Clinically this subject presented no features that differed from the other subjects carrying smaller repeat sizes.

CONCLUSIONS

We believe that the association of SCA 8 repeat expansions with sporadic, atypical and heterogeneous phenotypes is debatable and should be interpreted with caution. Our personal conclusion is that testing in such patients may become a source of diagnostic confusion.