SNP Shot: Genomic Insights

SCN8A-related epilepsy with encephalopathy is a disorder marked by recurring seizures (epilepsy), impaired brain function (encephalopathy), and intellectual disability. The symptoms typically appear in infancy.

The seizures associated with SCN8A-related epilepsy with encephalopathy can manifest in various forms, including infantile spasms (involuntary muscle contractions before age 1), absence seizures (partial or complete loss of consciousness), myoclonic seizures (involuntary muscle twitches), and tonic-clonic seizures (loss of consciousness with muscle rigidity and convulsions). Many individuals with this condition experience multiple seizure types. Seizure frequency varies widely, from numerous daily episodes to less than one per month. Often, the seizures are considered refractory, meaning they are resistant to treatment with anti-epileptic drugs.

Besides seizures, SCN8A-related epilepsy with encephalopathy can also lead to intellectual disability, ranging from mild to severe. Some infants initially develop normally but then experience developmental regression, losing previously learned abilities, and cognitive decline as epilepsy emerges. Movement problems are also prevalent, with about half of affected infants unable to perform voluntary movements. Behavioral issues are also possible.

In rare instances, individuals with this condition may experience sudden unexpected death in epilepsy (SUDEP), with no identifiable cause.

Inheritance:

SCN8A-related epilepsy with encephalopathy is inherited in an autosomal dominant manner. This means that only one copy of the mutated gene in each cell is enough to cause the disorder. Most cases arise from new (de novo) mutations in the gene during the formation of egg or sperm cells, or in early embryonic development. Consequently, most affected individuals have no family history of the condition.