A 9-year-old girl, who had no family history of neurologic diseases in the first-degree relatives, had a 3-year history of progressive myoclonus epilepsy (PME). A thorough laboratory investigation was normal. As two sisters of her paternal grandmother were said to have Huntington's disease (HD), the authors looked for HD and found a CAG repeat expansion of 115 repeats. This diagnosis should be considered in addition to other causes in patients with PME. Moreover, the current case further supports the notion that HD should be considered even when a family history is not obvious.