KCNB1 encephalopathy

KCNB1 encephalopathy is a condition characterized by abnormal brain function (encephalopathy), recurrent seizures (epilepsy), and developmental delay.

Most people who have KCNB1 encephalopathy have more than one type of seizure. The seizure types that can occur in people with this condition include uncontrolled muscle twitches (myoclonic seizures), uncontrolled muscle stiffness (tonic seizures), loss of consciousness with muscle rigidity and convulsions (tonic-clonic seizures), sudden episodes of weak muscle tone (atonic seizures), sudden falls (drop attacks), or partial or complete loss of consciousness (absence seizures).

Some individuals with KCNB1 encephalopathy do not develop seizures, but they do have an abnormal pattern of electrical activity in the brain called continuous spike and waves during slow-wave sleep (CSWS). This pattern occurs during sleep, specifically during deep (slow-wave) sleep.

Children with KCNB1 encephalopathy have delayed development of speech and motor skills, such as sitting, crawling, and walking. Weak muscle tone (hypotonia) in some affected individuals can contribute to this delay. Many children with the condition eventually walk independently, but some individuals require assistance. Some affected individuals can communicate verbally using simple sentences, while others never develop the skill.

About half of individuals with KCNB1 encephalopathy also have neurodevelopmental disorders, including attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD). In KCNB1 encephalopathy, problems with vision, digestion, and sleep can rarely occur.