Hyperkinesia and early-onset dementia in a female with co-occurring PSEN1 and HTT mutations: A case report.

A middle-aged female with family history of early-onset dementia presented with progressive amnesia, behavioral dysregulation, and myoclonus. Workup revealed pathogenic PSEN1 variant and intermediate HTT allele (30 CAG repeats). This case illustrates that motor symptoms should not be neglected in early-onset familial Alzheimer's disease (EOFAD). Moreover, hyperkinetic phenomenology does not reliably differentiate EOFAD and Huntington's disease (HD) due to the possibility of co-occurring mutations. Patients undergoing EOFAD evaluation should be screened for HD as well. Finally, this first case of presenilin mutation and abnormal huntingtin in the same patient suggests that EOFAD and HD can genetically co-occur.