Progressive myoclonus epilepsy caused by a gain-of-function KCNA2 mutation

We describe the novel phenotypic features of an adult male patient carrying a p.Arg297Gln (c.890 G > A) mutation of the KCNA2 gene encoding the voltage-gated potassium channel KV1.2. This mutation has been previously reported in patients presenting with epileptic encephalopathy (MIM # 616366) and early-onset polymorphic seizures [1–3] but, unlike the other cases, the clinical aspects of our patient included prominent and worsening action myoclonus consistent with progressive myoclonus epilepsy (PME).