[Genotype and phenotype of children with KCNA2 gene related developmental and epileptic encephalopathy]

Objective: To investigate the genotype and phenotype of children with KCNA2 gene related developmental and epileptic encephalopathy (DEE). Methods: Clinical data including the manifestations and electroencephalogram of 8 children with KCNA2 variants treated in the Department of Pediatrics, Peking University First Hospital from March 2017 to June 2019 were collected and analyzed retrospectively. Results: Among the 8 epileptic patients with KCNA2 variants, 5 were males and 3 were females. The age of onset was from 1 day to 11 months. The age at last follow-up ranged from 4 months to 86 months. Two variants including c.1214C>T (loss-of-function) and c.1120A>G (gain-and loss-of-function) were identified. The variant of c.1214C>T was found in six patients (case 1-6). For these patients, the age of onset was from 5 to 11 months and they were characterized by multiple seizure types. All had focal seizures and had normal development before seizure onset with developmental regression after seizure onset. The first electroencephalogram showed epileptic discharges in Rolandic region in two, epileptic discharges in Rolandic region combined with generalized discharge in one, generalized discharge with posterior predominance in two (combined with or transferred to Rolandic region during the course) and epileptic discharges in posterior region combined with generalized discharge in one. And in 5 of them the Rolandic discharges developed into epileptic electrical status (ESES) during sleep. All the six patients were still treated with a combination of multiple antiepileptic drugs. Two of them had seizure controlled at 80 months and 68 months, respectively. The variant of c.1120A>G were identified in two of eight patients (case 7 and 8) and they had seizure onset on the 1st day after birth. Their epileptic seizures were frequent and difficult to control. They had remarkably developmental delay and microcephaly since birth. One case (case 8) had a wide forehead. They had frequent seizures up to the last follow-up. In case 7, the early electroencephalogram showed epileptic discharges in temporal region, and interictal electroencephalogram at 3 months of age showed multifocal discharge with posterior and temporal region predominance. In case 8, the early electroencephalogram was normal and electroencephalogram showed burst suppression at 2 months of age, and it developed epileptiform discharge in posterior region at 1 year of age. Conclusions: KCNA2 gene variants can lead to DEE with multiple seizures types. Among them, loss-of-function c.1214C>T is the most common, and these patients have seizure onset at infancy with Rolandic discharges tended to develop into to ESES pattern. The variant of c.1120A>G is a gain-of- and loss-of-function variant, patients with c.1120A>G have seizure onset in neonatal period, the phenotype overlaps with the former but is more severe.