Encephalopathy related to status epilepticus during sleep due to a de novo KCNA1 variant in the Kv-specific Pro-Val-Pro motif: phenotypic description and remarkable electroclinical response to ACTH.

Although the classic phenotype of episodic ataxia type 1 (EA1) caused by variants in KCNA1 includes episodic ataxia and myokymia, further genotype-phenotype correlations are difficult to establish due to highly heterogeneous clinical presentations associated with KCNA1 pathogenic variants. De novo variants in the paralogous Pro-Val-Pro motif (PVP) of KCNA2, an essential region for channel gating, have been reported to be associated with severe epilepsy phenotypes, including developmental and epileptic encephalopathies (DEE). Here, we describe the first patient with a DEE who developed an encephalopathy related to status epilepticus during sleep (ESES) and cerebellar signs, harbouring a variant in the Kv-specific PVP motif of the KCNA1 gene. Interestingly, he showed a remarkable long-term electroclinical response to IM ACTH therapy. This report extends the range of phenotypes associated with KCNA1 variants to include that of ESES, and suggests that ACTH therapy is likely to have a positive effect in patients with these variants.