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Disease Profile

Juvenile myoclonic epilepsy

Prevalence
Prevalence estimates on Rare Medical Network websites are calculated based on data available from numerous sources, including US and European government statistics, the NIH, Orphanet, and published epidemiologic studies. Rare disease population data is recognized to be highly variable, and based on a wide variety of source data and methodologies, so the prevalence data on this site should be assumed to be estimated and cannot be considered to be absolutely correct.

Unknown

Age of onset

Adolescent

ICD-10

G40.3

Inheritance

Autosomal dominant A pathogenic variant in only one gene copy in each cell is sufficient to cause an autosomal dominant disease

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Autosomal recessive Pathogenic variants in both copies of each gene of the chromosome are needed to cause an autosomal recessive disease and observe the mutant phenotype

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X-linked
dominant X-linked dominant inheritance, sometimes referred to as X-linked dominance, is a mode of genetic inheritance by which a dominant gene is carried on the X chromosome.

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X-linked
recessive Pathogenic variants in both copies of a gene on the X chromosome cause an X-linked recessive disorder

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Mitochondrial or multigenic Mitochondrial genetic disorders can be caused by changes (mutations) in either the mitochondrial DNA or nuclear DNA that lead to dysfunction of the mitochondria and inadequate production of energy.

Multigenic or multifactor Inheritance involving many factors, of which at least one is genetic but none is of overwhelming importance, as in the causation of a disease by multiple genetic and environmental factors.

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Not applicable

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Other names (AKA)

Petit mal, impulsive; JME; EJM;

Summary

Juvenile myoclonic epilepsy is an epilepsy syndrome characterized by myoclonic jerks (quick jerks of the arms or legs), generalized tonic-clonic seizures (GTCSs), and sometimes, absence seizures. The seizures of juvenile myoclonic epilepsy often occur when people first awaken in the morning. Seizures can be triggered by lack of sleep, extreme fatigue, stress, or alcohol consumption. Onset typically occurs around adolesence in otherwise healthy children.[1][2][3] The causes of juvenile myoclonic epilepsy are very complex and not completely understood. Mutations in one of several genes, including the GABRA1 and the EFHC1 genes, can cause or increase susceptibility to this condition. Although patients usually require lifelong treatment with anticonvulsants, their overall prognosis is generally good.[1][2]

Symptoms

The signs and symptoms of juvenile myoclonic epilepsy are:[1][2]

  • Myoclonic jerks or seizures, which are described as quick jerks of the arms and legs, and are the hallmark feature of the disease; they may be the only symptom in about 17% of the cases; in about 20% of the cases, the seizures occur in clusters, affecting only one side (unilateral) of the body, and start before a tonic-clonic seizure
  • Generalized tonic-clonic seizures, appear a few months after onset of myoclonic jerks
  • Absence seizures, usually the first symptom to present around 5 and 16 years of age
  • Myoclonic status epilepticus is considered to be the most concerning problem of juvenile myoclonic epilepsy. It occurs when multiple myoclonic seizures do not readily stop and after sleep deprivation or missing medications.

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

Medical Terms Other Names
Learn More:
HPO ID
Percent of people who have these symptoms is not available through HPO
Autosomal dominant inheritance
0000006
Bilateral tonic-clonic seizure
Grand mal seizures
0002069
EEG with generalized polyspikes
0012001
Generalized non-motor (absence) seizure
Brief seizures with staring spells
0002121
Morning myoclonic jerks
0007000
Status epilepticus
Repeated seizures without recovery between them
0002133

Cause

The exact cause of juvenile myoclonic epilepsy remains unknown. It is not associated with conditions such as head trauma, brain tumor, or encephalitis.

Family history and genetic factors play a strong role in the risk for juvenile myoclonic epilepsy. About one third of affected people have a relative with epileptic seizures, and in several families, specific genetic mutations have been found.[1] Mutations in the GABRA1 and EFHC1 genes, and other genes, not yet identified, can cause or may increase susceptibility to juvenile myoclonic epilepsy.[3]

The GABRA1 gene provides instructions for making a protein involved with the influx of chloride ions crossing the cell membrane. The influx of chloride ions creates an environment in the cell that inhibits signaling between nerve cells (neurons) and prevents the brain from being overloaded with too many signals. Mutations in the GABRA1 gene lead to overstimulation of neurons in the brain, and triggers the abnormal brain activity associated with seizures.[3]

Mutations in the EFHC1 gene have been associated with juvenile myoclonic epilepsy in a small number of people. The EFHC1 gene provides instructions for making a protein that also plays a role in neuron activity, although its function is not completely understood, but that may also lead to overstimulation of neurons and trigger seizures.[3]

In people with juvenile myoclonic epilepsy, symptoms can be brought on by:[1][4]

  • Sleep deprivation
  • Psychological stress
  • Alcohol and drug use
  • Noncompliance of medication
  • Flickering lights such as strobe lights 
  • Menses
  • Time of day usually mornings

Diagnosis

Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.

Testing Resources

  • The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

    Treatment

    Avoiding precipitating events such as alcohol use and sleep deprivation may be useful. However, medical therapy with anti-convulsants is typically needed and well tolerated. The majority of patients can be well-controlled on a single drug, most commonly valproic acid. Other medications that might be used separately or in combination include lamotrigine, levetiracetam, clonazepam, and topiramate.[1][2] 

    More details about the medications used to treat juvenile myoclonic epilepsy are available through Medscape Reference and the Epilepsy Foundation

    Organizations

    Support and advocacy groups can help you connect with other patients and families, and they can provide valuable services. Many develop patient-centered information and are the driving force behind research for better treatments and possible cures. They can direct you to research, resources, and services. Many organizations also have experts who serve as medical advisors or provide lists of doctors/clinics. Visit the group’s website or contact them to learn about the services they offer. Inclusion on this list is not an endorsement by GARD.

    Organizations Providing General Support

      Learn more

      These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

      Where to Start

        In-Depth Information

        • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
        • The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
        • Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine. 
        • PubMed is a searchable database of medical literature and lists journal articles that discuss Juvenile myoclonic epilepsy. Click on the link to view a sample search on this topic.

          References

          1. James Selph. Juvenile Myoclonic Epilepsy. Medscape Reference. June 24, 2016; https://emedicine.medscape.com/article/1185061-overview.
          2. Sirven J, Fisher R. Juvenile Myoclonic Epilepsy. Epilepsy Foundation. September 2013; https://www.epilepsy.com/learn/types-epilepsy-syndromes/juvenile-myoclonic-epilepsy.
          3. Juvenile Myoclonic Epilepsy. Genetics Home Reference (GHR). September 2015; https://ghr.nlm.nih.gov/condition/juvenile-myoclonic-epilepsy.
          4. Juvenile Myoclonic Epilepsy. Epilepsy Foundation. 9/2013; https://www.epilepsy.com/learn/types-epilepsy-syndromes/juvenile-myoclonic-epilepsy.

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