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seizure","onset_id":null,"reference":"OMIM:254780","source_release":"2026-06-23"},"sourceGroups":["omim"]}],"referenceLabels":{},"references":{"causeHtml":"<ul><li><a href=\"https://medlineplus.gov/genetics/condition/lafora-progressive-myoclonus-epilepsy\">Lafora progressive myoclonus epilepsy</a></li></ul>","identityNote":"MONDO cross-references identify native condition entries. Ancestor membership does not transfer phenotype values between groups.","importantHtml":""},"sections":[{"bodyHtml":"<p>Lafora progressive myoclonus epilepsy can be caused by mutations in either the EPM2A gene or the NHLRC1 gene. These genes provide instructions for making proteins called laforin and malin, respectively. Laforin and malin play a critical role in the survival of nerve cells (neurons) in the brain.</p><p>Studies suggest that laforin and malin work together and may have several functions. One of these is to help regulate the production of a complex sugar called glycogen, which is a major source of stored energy in the body. The body stores this sugar in the liver and muscles, breaking it down when it is needed for fuel. Laforin and malin may prevent a potentially damaging buildup of glycogen in tissues that do not normally store this molecule, such as those of the nervous system.</p><p>Researchers have discovered that people with Lafora progressive myoclonus epilepsy have distinctive clumps called Lafora bodies within their cells. Lafora bodies are made up of an abnormal form of glycogen that cannot be broken down and used for fuel. Instead, it builds up to form clumps that can damage cells. Neurons appear to be particularly vulnerable to this type of damage. Although Lafora bodies are found in many of the body&#x27;s tissues, the signs and symptoms of Lafora progressive myoclonus epilepsy are limited to the nervous system.</p><p>Mutations in the EPM2A gene prevent cells from making functional laforin, while NHLRC1 gene mutations prevent the production of functional malin. It is unclear how a loss of either of these proteins leads to the formation of Lafora bodies. However, a loss of laforin or malin ultimately results in the death of neurons, which interferes with the brain&#x27;s normal functions. The condition tends to progress more slowly in some people with NHLRC1 gene mutations than in those with EPM2A gene mutations.</p><p>Mutations in the EPM2A and NHLRC1 genes account for 80 percent to 90 percent of all cases of Lafora progressive myoclonus epilepsy. In the remaining cases, the cause of the condition is unknown. Researchers are searching for other genetic changes that may underlie this disease.</p><p class=\"section-source\"><a href=\"https://medlineplus.gov/genetics/condition/lafora-progressive-myoclonus-epilepsy/#causes\">MedlinePlus Genetics: Causes</a></p>","key":"forms","title":"What causes Lafora progressive myoclonus epilepsy?"},{"bodyHtml":"<p>Myoclonus is a term used to describe episodes of sudden, involuntary muscle jerking or twitching that can affect part of the body or the entire body. Myoclonus can occur when an affected person is at rest, and it is made worse by motion, excitement, or flashing light (photic stimulation). In the later stages of Lafora progressive myoclonus epilepsy, myoclonus often occurs continuously and affects the entire body.</p><p>Several types of seizures commonly occur in people with Lafora progressive myoclonus epilepsy. Generalized tonic-clonic seizures (also known as grand mal seizures) affect the entire body, causing muscle rigidity, convulsions, and loss of consciousness. Affected individuals may also experience occipital seizures, which can cause temporary blindness and visual hallucinations. Over time, the seizures worsen and become more difficult to treat. A life-threatening seizure condition called status epilepticus may also develop. Status epilepticus is a continuous state of seizure activity lasting longer than several minutes.</p><p>About the same time seizures begin, intellectual function starts to decline. Behavioral changes, depression, confusion, and speech difficulties (dysarthria) are among the early signs and symptoms of this disorder. As the condition worsens, a continued loss of intellectual function (dementia) impairs memory, judgment, and thought. Affected people lose the ability to perform the activities of daily living by their mid-twenties, and they ultimately require comprehensive care. People with Lafora progressive myoclonus epilepsy generally survive up to 10 years after symptoms first appear.</p><p class=\"section-source\">Source: <a href=\"https://medlineplus.gov/genetics/condition/lafora-progressive-myoclonus-epilepsy\">MedlinePlus Genetics</a></p>","key":"overview","title":"Condition overview"}],"sharedSources":[],"slug":"lafora-progressive-myoclonus-epilepsy","sourceDocuments":[{"name":"Lafora progressive myoclonus epilepsy","reviewed":"2009-07","sections":{"causes":{"fetchedAt":"2026-10-20T20:22:47.295774+00:00","label":"Causes","pageSha256":"64226b5d6c5d186d4655d08b2aab9dcfea036b27240b9e863fa356f7f1ba1b53","sourceUrl":"https://medlineplus.gov/genetics/condition/lafora-progressive-myoclonus-epilepsy/#causes","status":"available"}},"source_release":"2026-10-01","url":"https://medlineplus.gov/genetics/condition/lafora-progressive-myoclonus-epilepsy"}],"sourceNote":"MedlinePlus descriptions and Causes; original HPO annotations.","takeawayHtml":"Cause explanations are from MedlinePlus Genetics. Feature values below retain their original sources and patient groups.","title":"Lafora progressive myoclonus epilepsy"},"schemaVersion":1}