[De novo SCN1A gene deletion in therapy-resistant Dravet syndrome].

Severe myoclonic epilepsy in infancy (Dravet's syndrome) is a very rare form of epilepsy. Mutations of SCN1A gene encoding voltage-gated sodium channel alpha-1 subunit are major causes of the autosomal dominant disorder. Most cases are associated with a de novo point mutation, but some patients have copy number variations. The protein encoded by the SCN1A gene plays a role in the generation and propagation of action potentials. Loss of function caused by the majority of gene mutations leads to hyperexcitability of the neuronal network that finally results in the formation of the epileptic seizures. Molecular genetic test for copy number variations of SCN1A gene is available in the department of the authors since 2013 besides sequencing analysis of the whole gene. This article presents the case of a 7-year-old patient with two years of recorded patient history outside of the author's department. Molecular genetic test, which detected a de novo SCN1A gene deletion in heterozygous form, revealed SCN1A gene associated monogenic epileptic syndrome being in the genetic background of therapy-resistant seizures.