8p deletion and 9p duplication in two children with electrical status epilepticus in sleep syndrome.

We describe two individuals with the same chromosomal aberrations derived from an unbalanced translocation between chromosomes 8p and 9p, who presented with intellectual disabilities, dysmorphic features, and localization-related epilepsy. Several years after the onset of epilepsy, aggravation of widespread epileptic discharges during sleep resulted in the emergence of absence and/or atonic seizures in both patients; one patient additionally presented with psychomotor deterioration. These symptoms completely disappeared after treatment with ethosuximide and benzodiazepines, and marked improvement was observed in electroencephalographic findings. We review the clinical features of der(8)t(8;9) with particular focus on epileptic complications. We conclude that particular types of chromosomal aberrations may have a propensity to develop the condition categorized as electrical status epilepticus in sleep.