The unique co-occurrence of spinocerebellar ataxia type 10 (SCA10) and Huntington disease

We present a unique thirty-nine year old woman with both Huntington's disease (HD) and spinocerebellar ataxia type 10 (SCA10). She has 48 CAG repeats in the HD gene and 2511 ATTCT repeats in the ATX10 gene. Although both conditions are repeat expansion diseases they are thought to have quite different pathogenic mechanisms. The symptomatic age of onset in this patient (mid30s) is within the expected range for her repeat expansion sizes for each condition, but we discuss the evidence that the two conditions may interact to produce a more severe cognitive phenotype than would be expected for either of the conditions independently. The subject has Amerindian background on the maternal side from Colombia, South America, thus adding a 5th country expressing SCA10, all with Amerindian ancestry.