A case of SCN8A-related developmental epileptic encephalopathy diagnosed by clinical speculation driven targeted DNA sequencing and remission of epilepsy by sodium channel blockers combination therapy

Background

SCN8A-related epilepsy and/or neurodevelopmental disorders encompass a very broad spectrum of phenotypes. The most severe form, SCN8A developmental and epileptic encephalopathy (DEE), develops intractable epilepsy from early infancy and can lead to sudden death. Early diagnosis and therapeutic intervention are essential, but diagnosis is based on genetic testing and definitive diagnosis is often delayed.

Case report

A 4-month-old girl presented with intractable epilepsy. Most antiepileptic drugs were ineffective, but high doses of phenytoin suppressed seizures, so a sodium channelopathy was suspected and targeted DNA sequencing was performed, which revealed a pathogenic missense variant Val1315Met in the SCN8A gene. Based on the diagnosis, combination therapy with sodium channel blockers (SCBs) was initiated and the seizures resolved.

Conclusion

We experienced SCN8A-DEE, which led to early diagnosis based on clinical course and improved prognosis. It is noteworthy that even when the effect of a single SCB is insufficient, as in this case, combination therapy can lead to seizure free in SCN8A-DEE.