Zonisamide-responsive myoclonus in SEMA6B-associated progressive myoclonic epilepsy

We present a female patient in her early twenties with global development delay, progressive ataxia, epilepsy, and myoclonus caused by a stop mutation in the SEMA6B gene. Truncating DNA variants located in the last exon of SEMA6B have recently been identified as a cause of autosomal dominant progressive myoclonus epilepsy. In many cases, myoclonus in the context of progressive myoclonic epilepsy is refractory to medical treatment. In the present case, treatment with zonisamide caused clinical improvement, particularly of positive and negative truncal myoclonus, considerably improving patient's gait and thus mobility.

Automated summary

A female patient in her early twenties presented with global development delay, progressive ataxia, epilepsy, and myoclonus caused by a stop mutation in the SEMA6B gene. Treatment with zonisamide resulted in significant clinical improvement, particularly in truncal myoclonus, improving the patient's gait and mobility.