SCN1A and progressive myoclonus epilepsy: In addition, there are 2 further individuals reported with the Thr226Met mutation.2,8 One is a child described as having progressive myoclonus epilepsy; however, the limited available clinical information suggests that the phenotype of this child could be consistent with early infantile SCN1A encephalopathy.8 Overlap between the movement disorder and a progressive myoclonus epilepsy could be challenging to distinguish, especially given that the patient was middle-aged at the time of review.