Myoclonic epilepsy of late onset in trisomy 21.

We report the case of a patient with trisomy 21 (T21) with late onset epilepsy. The electroclinical features were of myoclonic jerks on awakening and generalised tonic clonic seizures, with generalised spike and wave on EEG, and a progressive dementia. As familial Alzheimer's dementia and progressive myoclonic epilepsy (Unverricht-Lundborg type) are both linked to the chromosome 21, this case may represent a distinct progressive myoclonic epilepsy related to T21.