Progressive Myoclonic Epilepsies (PME) are a rare group of inherited neurodegenerative diseases characterized by myoclonus, resistance to treatment, and neurological deterioration. The cause of PME depends largely on the type of PME. Most PMEs are caused by autosomal dominant or recessive and mitochondrial mutations. The location of the mutation also affects the inheritance and treatment of PME. Diagnosing PME is difficult due to their genetic heterogeneity and the lack of a genetic mutation identified in some patients. The prognosis depends largely on the worsening symptoms and failure to respond to treatment. There is no current cure for PME and treatment focuses on managing myoclonus and seizures through antiepileptic medication (AED).The age of onset depends on the specific PME but PME can affect people of all ages. In Unverricht-Lundborg disease (ULD) the age of onset is between 6–15 years, while in Adult Neuronal ceroid lipofuscinoses (Adult NCL) the age of onset can be as late as 30.Symptoms often include action or stimuli induced myoclonus, seizures, neuropathy, cognitive decline, and spike and wave or no cerebral discharges. The prognosis of those diagnosed with PME is poor. The person often becomes reliant on a wheelchair, enters a vegetative state due to myoclonus, and has a shortened life expectancy. Signs and symptoms
The most common symptom of PME is myoclonus. The myoclonus can be fragmented or multifocal and can be triggered by posture, actions, and external stimuli such as light, sound, and touch. The type of myoclonus differs between the types of PME.
The symptoms are progressive, and individuals with MEAK often need to use a wheelchair by their late teenage years because of movement difficulties and myoclonus. Many individuals with MEAK report temporary improvement of symptoms when they have a high fever. Seizures may become less frequent in adulthood, but other neurological complications, including myoclonus, ataxia and tremor, may worsen. Myoclonic epilepsy and ataxia due to potassium (K+) channel mutation (MEAK) is caused by a specific pathogenic variant ("mutation") in KCNC1 (c. 959G>A; p.Arg320His). KCNC1-related developmental and epileptic encephalopathy is associated with other pathogenic variants in KCNC1. In most individuals with KCNC1-related disorders, the pathogenic KCNC1 variant occurred spontaneously (de novo) and was not inherited from either parent. Epidemiology
PME accounts for less than 1% of epilepsy cases at specialist centres. The incidence and prevalence of PME is unknown, but there are considerable geography and ethnic variations amongst the specific genetic disorders. One cause, Unverricht Lundborg Disease, has an incidence of at least 1:20,000 in Finland. See also
Juvenile myoclonic epilepsy
Spinal muscular atrophy with progressive myoclonic epilepsy

References
External links

GeneReview/NCBI/NIH/UW entry on Progressive Myoclonus Epilepsy with Ataxia