Spinocerebellar ataxia type 10 (SCA10) is an autosomal-dominant disorder caused by an expanded pentanucleotide repeat in the ATXN10 gene. This repeat expansion, when fully penetrant, has a size of 850 to 4500 repeats. It has been shown that the repeat composition can be a modifier of disease, e.g., seizures.Here, we describe a Hispanic kindred in which we identified both pure (ATTCT)n expansions and mixed (ATTCT)n-(ATTCC)n in the same family. We used No-Amp targeted sequencing and optical genome mapping to decipher the composition of these repeat expansions.