ObjectiveTo study the phenotype of children with KCNQ2 gene related epilepsy.MethodsForty epilepsy children who were detected with KCNQ2 gene variants were enrolled. Their genotype and phenotype were analyzed.ResultsThirty-six KCNQ2 variants were identified. Twenty variants were novel. Twelve patients had inherited variants, and 28 patients had de novo variants. The age of seizure onset was from one day to 9 months. 80.0% patients had their seizure onset in neonates (32/40). Multiple seizure types were observed. Focal seizure was observed in 38 patients (95.0%). Epileptic spasm was observed in 10 patients (25.0%). Myoclonic seizure was observed in 4 patients. Tonic spasm seizure was observed in 3 patients. In all patients, seizures manifested in clusters. In 28 patients with de novo KCNQ2 variants, 24 had development delay (85.7%), the other 4 patients had normal development. In 12 patients with inherited KCNQ2 variants, one had development delay, the other 11 patients had normal development (91.7%). The most common interictal EEG changes were local epilepsy discharges (31/40). The MRI of brain was abnormal in 14 patients with de novo KCNQ2 variants and developmental delay. The agenesis of corpus callosum was identified in 10 patient (25.0%). Enlargement of subarachnoid spaces in the frontal and temporal region was identified in 11 patients (27.5%). Cortial dysplasia in the bilateral frontal and temporal region was identified in 2 patients. Sulus deepening was identified in 4 patients. Enlargement of bilateral lateral ventricle was identified in 3 patients. In 40 patients with KCNQ2 variants, 3 were diagnosed as benign familial neonatal epilepsy (BFNE), 2 were diagnosed as benign familial neonatal-infantile epilepsy (BFNIE), 3 were benign familial infantile epilepsy (BFIE), 3 were benign infantile epilepsy (BIE), 5 were benign neonatal epilepsy (BNE), 3 wer Ohtahara syndrome (OS), 9 were West syndrome (WS), 12 were unclassified early infantile epileptic encephalopathy (EIEE), one was epilepsy with autism. Sodium channel blockers oxcarbazepine was the most effective among antiepileptic drugs, with a effective rate of 90.9%.ConclusionsMost KCNQ2 variants are missense variants. De novo variants are more common in patients with KCNQ2 variants. The clinical features of patients with KCNQ2 variants including that mainly with seizure onset in neonate, the main seizure type is focal seizures, seizures occur in clusters. Patients with de novo KCNQ2 variants often had developmental delay, and about half of them had frontal and temporal lobe dysplasia and agenesis of corpus callosum. Sodium channel blockers are effective agents for epilepsy patients with KCNQ2 variants.
ObjectiveBenign familial epilepsies that present themselves in the first year of life include benign familial neonatal epilepsy (BFNE), benign familial neonatal-infantile epilepsy (BFNIE) and benign familial infantile epilepsy (BFIE). We aim to investigate gene mutations and the relationship between genotypes and clinical phenotypes in benign familial epilepsies in the first year of life.MethodsWe recruited families with benign familial epilepsies in the first year of life at Peking University First Hospital from September 2006 to January 2018. Clinical information and blood samples were obtained from probands and their family members. For BFIE families, mutation screening of PRRT2 was performed by using the polymerase chain reaction (PCR) and Sanger sequencing at first. The PRRT2 mutation negative probands of BFIE families were further screened for pathogenic mutations by targeted next-generation sequencing. The probands of BFNE and BFNIE families were screened for pathogenic mutations by targeted next-generation sequencing.ResultsA total of 89 families with benign familial epilepsies in the first year of life were collected. Of the 89 families, 4 were classified as BFNE, 7 as BFNIE, and 78 as BFIE. Genetic testing led to the identification of gene mutations in 68 families (76.4%), including 50 families had PRRT2 mutations (hotspot mutation c.649dupC was detected in 32 families; c.649delC was detected in 6 families), 9 families had KCNQ2 mutations, 8 families had SCN2A mutations, and one family had GABRA6 mutation. In the 4 BFNE families, causative mutations were only found in KCNQ2, which was identified as the causative gene in 3 families. The remaining one BFNE family was not detected with any pathogenic mutation. All 7 BFNIE families had identifiable gene mutations, KCNQ2 was found in 3 families, SCN2A in 3 families, and PRRT2 in one family. In the 78 BFIE families, gene mutations were identified in 58 families (74.4%), with PRRT2 mutations found in 49 families (62.8%), SCN2A mutations found in 5 families, KCNQ2 mutations found in 3 families, and a novol GABRA6 mutation found in one family. Twenty BFIE families were not identified with any gene mutations. In 78 BFIE families, 18 were subclassified as infantile convulsions with paroxysmal choreoathetosis syndrome(ICCA). 17 of 18 ICCA families were detected with PRRT2 mutations (17/18, 94.4%). The remaining ICCA family was not detected with any pathogenic mutation.ConclusionsOur results confirmed that mutations in KCNQ2, SCN2A, and PRRT2 are major genetic causes of benign familial epilepsy in the first year of life in the Chinese population. KCNQ2 is the major gene related to BFNE. PRRT2 is the main gene responsible for BFIE. KCNQ2 and SCN2A mutations are common in BFNIE families. GABRA6 mutation might be a new cause of BFIE. Identification of underlying gene mutation can be helpful for clinical diagnosis and judgement of the prognosis.