Juvenile Myoclonic Epilepsy

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Juvenile myoclonic epilepsy is a condition characterized by recurrent seizures (epilepsy). This condition begins in childhood or adolescence, usually between ages 12 and 18, and lasts into adulthood. The most common type of seizure in people with this condition is myoclonic seizures, which cause rapid, uncontrolled muscle jerks. People with this condition may also have generalized tonic-clonic seizures (also known as grand mal seizures), which cause muscle rigidity, convulsions, and loss of consciousness. Sometimes, affected individuals have absence seizures, which cause loss of consciousness for a short period that appears as a staring spell. Typically, people with juvenile myoclonic epilepsy develop the characteristic myoclonic seizures in adolescence, then develop generalized tonic-clonic seizures a few years later. Although seizures can happen at any time, they occur most commonly in the morning, shortly after awakening. Seizures can be triggered by a lack of sleep, extreme tiredness, stress, or alcohol consumption.

The genetics of juvenile myoclonic epilepsy are complex and not completely understood. Mutations in one of several genes can cause or increase susceptibility to this condition. The most studied of these genes are the GABRA1 gene and the EFHC1 gene, although mutations in at least three other genes have been identified in people with this condition. Many people with juvenile myoclonic epilepsy do not have mutations in any of these genes. Changes in other, unidentified genes are likely involved in this condition.

Juvenile myoclonic epilepsy affects an estimated 1 in 1,000 people worldwide. Approximately 5 percent of people with epilepsy have juvenile myoclonic epilepsy.

The inheritance pattern of juvenile myoclonic epilepsy is not completely understood. When the condition is caused by mutations in the GABRA1 gene, it is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. The inheritance pattern of juvenile myoclonic epilepsy caused by mutations in the EFHC1 gene is not known.

Published Date: September 01, 2015
Published By: National Institutes of Health