PP07.15 – 2633: Familial generalized epilepsy with absences with SCN9A mutation: Therapy with carbamazepine

Objective Mutations of the SCN9A gene can cause ion channel dependant pain syndromes, generalized epilepsy with febrile seizures or familial febrile seizures, following an autosomal dominant or recessive inheritance. Furthermore cardiac symptoms such as bradycardia with syncopes up to asystole and tachycardia have been described. We present a case of a familial generalized epilepsy with additional paroxysmal tachycardia that has successfully been treated with carbamazepine. Case description Our 5-year-old patient first had absence-like seizures at the age of 3 years, with a frequency of approximately twice a month and a duration of 5 to 10 seconds. The EEG showed paroxysmal generalized polyspike wave complexes. Since the age of 4 years the patient had also suffered from episodes with paroxysmal tachycardia. The patient's mother and her sister had similar seizures in early childhood, both were successfully treated with carbamazepine (CBZ). The mother also suffers from episodes with paroxysmal tachycardia which are accompanied by panic attacks. In our patient, the heterozygous modification c.684C>G; p.I228M was detected in the SCN9A gene, using “next generation sequencing”. The mutation could also be detected in the patient's mother. A therapy with CBZ reduced both the boy's seizure frequency and the frequency of his paroxysmal tachycardia significantly. Discussion SCN9A mutations have also been described for Dravet syndrome and familial febrile seizures, whereas our patient showed a familial absence-like generalized epilepsy in combination with paroxysmal tachycardia. Our patient, his mother and also his aunt were successfully treated with CBZ, which could suggest that the patient's c.684C>G; p.I228M mutation causes a “gain of function” of the Nav1.7 sodium channel. The additional cardiac symptoms could also be an effect of the SCN9A mutation.