Novel KCNB1 mutation associated with non-syndromic intellectual disability

Potassium voltage-gated channel subfamily b member 1 (kcnb1) encodes kv2.1 potassium channel of crucial role in hippocampal neuron excitation homeostasis. kcnb1 mutations are known to cause early-onset infantile epilepsy. to date, 10 kcnb1 mutations have been described in 11 patients. using whole-exome sequencing, we identified a novel de novo missense (c.1132g>c, p.v378l) kcnb1 mutation in a patient with global developmental delay, intellectual disability, severe speech impairment, but no episode of epilepsy until the lastly examined age of 6 years old. furthermore, she showed neuropsychiatric symptoms including hyperactivity with irritability, heteroaggressiveness, psychomotor instability and agitation. our observation might expand the phenotypic spectrum of kcnb1-related phenotypes and raises the issue of the occurrence of the epileptic phenotype.