Epilepsies Associated with KCNQ2 Complicated by Supraventricular Tachycardia Due to a De Novo Mutation in KCNQ2

Epilepsies associated with the KCNQ2 mutation are a spectrum of disorders, with clinical manifestations ranging from benign familial neonatal convulsion to early-onset epileptic encephalopathy, depending on the mutation type and location (such as up-stream control elements). Here, we report the case of an infant girl diagnosed with epilepsy due to a de novo mutation in KCNQ2 and more interestingly, complicated by supraventricular tachycardia. An infant girl was diagnosed with epilepsy, with the following manifestations: Onset of seizures at three months; generalized tonic-clonic seizures, frequent at the beginning; status epilepticus, followed by psychomotor development retrogression; generalized spike, spike-slow, and slow waves observed during ictal electroencephalography (EEG), normal interictal EEG, and cranial magnetic resonance imaging. Seizures were controlled after administering valproic acid, and the patient exhibited normal psychomotor development eventually. Targeted next-generation sequencing identified a previously unreported de novo mutation in KCNQ2 [c.553G>A; p.(Ala185Thr)]. Interestingly, the patient also exhibited supraventricular tachycardia, confirmed by electrocardiography. Although we concluded that seizure was the convulsive syncope resulting from arrhythmia, we conceived a link between the two events, which has been called “cardiocerebral” channelopathy. A de novo mutation in KCNQ2 causes epilepsy and the concurrent arrhythmia may be linked with this mutation.