BACKGROUND: Progressive Myoclonic Epilepsy (PME) is a group of rare diseases that are difficult to differentiate from one another based on phenotypical characteristics.
METHODS: We report a case of PME type 7 due to a pathogenic variant in KCNC1 with myoclonus improvement after epileptic seizures.
CONCLUSIONS: Myoclonus improvement after seizures may be a clue to the diagnosis of Progressive Myoclonic Epilepsy type 7.

Progressive myoclonic epilepsy (PME) is characterized by prominent myoclonus and generalized or focal seizures. A recently described novel KCNC1 mutation is associated with a specific phenotype of progressive myoclonic epilepsy, which has been defined as myoclonic epilepsy and ataxia due to potassium channel mutation (MEAK). Our case illustrates a typical presentation of this disease and the potential for misdiagnosis as idiopathic generalized epilepsy during the early phase of the disease. Unique findings that may suggest an alternative diagnosis are a progressive myoclonus, prominent ataxia/dysmetria on examination, and abnormally high amplitude in the sensory evoked potential recording. We also report a brief review of the existing literature on MEAK. Early and accurate diagnosis with genetic testing may significantly help in counseling patients and families.