Novel clinical manifestations in patients with KCNA2 mutations

Purpose: To report novel clinical manifestations of KCNA2 mutation related epileptic encephalopathy.

Methods: Blood samples were sent for whole exome and Sanger sequencing. Seizure types were characterized by clinical criteria and EEG recording.

Results: KCNA2 mutations have been reported in 10 cases who presented with focal, absence, generalized tonic-clonic or myoclonic astatic seizures. Here we describe 3 patients with previously unreported, more severe manifestations. Patient 1 is a 5 year-old male with a c.1214 C > T (p.Pro405Leu) mutation, previously reported to be disease causing. He presented at 1year of age with focal seizures and subsequently developed electrical status epilepticus of sleep at age 3. The latter finding to our knowledge has never been reported in patients with KCNA2 mutations. Patient 2 is a 7 year-old female with a novel c.1195 G > A (p.Val399Met) mutation not previously described. She presented with intermittent then continuous polymyoclonus and myoclonic-astatic and generalized tonic clonic seizures. Continuous polymyoclonus is another new manifestation in patients with KCNA2 mutations. Patient 3 is a 23 year-old male with a c.889C > T (p.Arg297Trp) mutation not previously described. He presented at 4 years of age with generalized tonic clonic seizures and later developed recurrent refractory status epilepticus episodes at ages 19, 22 and 23 years, the latter being a novel manifestation in patients with KCNA2 mutations.

Conclusion: We identified 3 patients with KCNA2 mutations with novel characteristics, including electrical status epilepticus of sleep, continuous polymyoclonus and status epilepticus. These results expand KCNA2 mutation epileptic manifestations to include more severe, previously unreported phenotypes.