Families

KCNB1 encephalopathy is caused by a change (variant/mutation) in one copy of the KCNB1 gene that prevents it from working properly.

The symptoms a child experiences and the severity of the disorder can vary widely.
Patients with KCNB1 disorders have difficulties in reaching milestones (delay in sitting, crawling and walking), often with prominent language impairment.
Most children develop multiple types of seizures that can be frequent and difficult to control with medications.
Some children may have features of autism spectrum disorders and movements disorders.

KCNB1-related disorder is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder.
In most children with KCNB1-related disorders, the pathogenic KCNB1 variant occurred accidently (de novo) and was not inherited from either parent.

In rare cases, the pathogenic KCNB1 variant has been passed on from an asymptomatic parent due to parental mosaicism. Just like a mosaic piece of art, in which each tile is different, a mosaic parent has distinct cell types. Most cells of a mosaic parent do not carry the pathogenic KCNB1 variant and he does not have the manifestation of the disease.