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KCNB1 encephalopathy
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Condition

KCNB1 encephalopathy

KCNB1 encephalopathy is a condition characterized by abnormal brain function, recurrent seizures, and developmental delays.

Overview

KCNB1 encephalopathy is a condition involving abnormal brain function (encephalopathy), recurrent seizures (epilepsy), and developmental delay. Many affected individuals experience multiple seizure types, including myoclonic, tonic, tonic-clonic, atonic, and absence seizures.

Developmental Impact

Children with this condition experience delayed development of speech and motor skills, such as sitting, crawling, and walking. Weak muscle tone (hypotonia) can contribute to these delays. About half of affected individuals also have neurodevelopmental disorders, including ADHD and autism spectrum disorder (ASD).

Some individuals do not have clinical seizures but exhibit an abnormal electrical pattern in the brain known as continuous spike and waves during slow-wave sleep (CSWS).

Causes

The condition is caused by mutations in the KCNB1 gene, which provides instructions for making a part of a potassium channel called Kv2.1. These channels transport potassium ions in and out of cells, playing a key role in generating and transmitting electrical signals in the brain.

Mutations lead to an altered protein that results in impaired Kv2.1 channel function. This disrupts the regulation of potassium ions in neurons, interfering with normal communication between cells and leading to seizures and intellectual disability.

Inheritance

This condition is inherited in an autosomal dominant pattern, meaning one copy of the altered gene in each cell is sufficient to cause the disorder. Most cases result from a new mutation and occur in people with no family history of the disorder.

Frequently Asked Questions

truly de novo mutation carries a low recurrence risk (<1 %) for subsequent children, but parental germline mosaicism can increase that risk. Therefore, both parents should undergo targeted testing for the specific KCNB1 variant to assess mosaicism and receive accurate recurrence counseling.
Look for hypotonia, delayed motor milestones such as sitting or crawling, delayed speech acquisition, and abnormal sleep‑related EEG patterns (e.g., continuous spike‑and‑wave during slow‑wave sleep) that occur before any clinical seizures.
Diagnosis is confirmed by molecular genetic testing—typically a targeted gene panel for epilepsy or whole‑exome sequencing—that identifies a pathogenic or likely‑pathogenic variant in the KCNB1 gene; results are interpreted alongside the clinical phenotype and EEG findings.
First‑line treatment usually involves broad‑spectrum antiepileptic drugs (e.g., levetiracetam, valproate, or clobazam); refractory cases may benefit from a ketogenic diet, vagus‑nerve stimulation, or newer agents such as fenfluramine. Early initiation of therapy and regular EEG monitoring are essential to adjust medication and minimize developmental impact.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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