Key result
Eight de novo variants of the HCN1 gene were identified in eight children with epilepsy and developmental delay, expanding the genotype and phenotype of HCN1-related epilepsy.
Why the study?
HCN ion channels are widely expressed in neurons and increasingly implicated in epilepsies, prompting investigation of HCN1 variants in patients with unexplained recurrent seizures and developmental delay.
What are the genetic variants and clinical phenotypes associated with HCN1-related childhood epilepsy in a Chinese cohort?
Observational (n=8)
What are the genetic variants and clinical phenotypes associated with HCN1-related childhood epilepsy in a Chinese cohort?
The study expands the known genotype and phenotype of HCN1-related epilepsy by identifying eight de novo variants, including five novel ones, in Chinese children.
De novo HCN1 variants may underlie unexplained epilepsy with developmental delay; extends candidate genes but remains hypothesis-generating.
OBJECTIVE: HCN ion channel family has a widespread expression in neurons, and recently, increasing studies have demonstrated their roles in epilepsies. METHODS: Clinical data of the patients were gathered in a retrospective study. Exon sequencing was used for the patients with unexplained recurrent seizures and varying levels of developmental delay. RESULTS: In this study, eight de novo variants of HCN1 genes were uncovered in eight patients, including six missense variants, one nonsense variant and one frameshift insertion variant; five of them were reported for the first time. The onset age for eight patients ranges from one month to one year. Their main clinical manifestations are epilepsy and varying degrees of developmental delay, and the main type of seizure is focal secondary generalized tonic-clonic seizure. Importantly, in our study, one case presented with a form of migrating focal seizure that has not been reported in the literature. Seizures from five of the eight children were effectively controlled with antiepileptic drugs including valproic acid, levetiracetam and oxcarbazepine. One child developed normally and four children developed mild delay. One child was treated with topiramate, and the convulsion was partially controlled and showed moderate to severe developmental delay. The antiepileptic treatment failed for the other two children, and the two children were treated with sodium valproate, oxcarbazepine, lamotrigine, chlorbazan, levetiracetam and nitrodiazepam successively, but their convulsions were not controlled and showed moderate to severe developmental delay. SIGNIFICANCE: Our research reported eight variants in HCN1 gene causing epilepsy; among these variants, five variants were never reported before. HCN1-related epilepsy usually starts infantile period, and focal secondary generalized tonic-clonic seizure is the most common seizure type. Importantly, we reported the case with migrating focal seizure was rarely reported. Our study expanded both genotype and phenotype for HCN1-related epilepsy.
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Yang et al. (2023) conducted an observational in Childhood epilepsy (n=8). HCN1 pathogenic variants was evaluated on Identification of HCN1 variants and clinical manifestations. Eight de novo variants of the HCN1 gene were identified in eight children with epilepsy and developmental delay, expanding the genotype and phenotype of HCN1-related epilepsy.
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