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.