Focal seizures and epileptic spasms in a child with Down syndrome from a family with a PRRT2 mutation.

We describe a girl with Down syndrome who experienced focal seizures and epileptic spasms during infancy. The patient was diagnosed as having trisomy 21 during the neonatal period. She had focal seizures at five months of age, which were controlled with phenobarbital. However, epileptic spasms appeared at seven months of age in association with hypsarrhythmia. Upon treatment with adrenocorticotropic hormone, her epileptic spasms disappeared. Her younger brother also had focal seizures at five months of age. His development and interictal electroencephalogram were normal. The patient's father had had infantile epilepsy and paroxysmal kinesigenic dyskinesia. We performed a mutation analysis of the PRRT2 gene and found a c.841T>C mutation in the present patient, her father, and in her younger brother. We hypothesized that the focal seizures in our patient were caused by the PRRT2 mutation, whereas the epileptic spasms were attributable to trisomy 21.