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Myoclonic Epilepsy Associated with Ragged-Red Fibe
Thursday, 05 May 2005
Thursday, 05 May 2005

What

MERRF is a genetic disorder that affects many different parts of the body and is characterized by sudden twitching of the muscles or parts of muscles (myoclonus), which is often the first symptom, and seizures. MERRF results when mitochondria do not function properly. Mitochondria are a part of all cells and function to produce energy; they are considered to be the “powerhouse” of a cell.

Who

MERRF is found in all ethnic groups and affects males and females equally. Signs and symptoms usually start in childhood, although in some cases the onset of the disease may be delayed until adolescence or adulthood. Mitochondria are only inherited from our mothers; therefore all children of an affected woman will be affected.

Signs and Symptoms

Children have normal early development and reach developmental milestones on time. Later, usually in childhood, signs and symptoms include;

  • myoclonus (sudden, involuntary jerking of muscles),
  • generalized epilepsy (seizures that are generalized, not localized to a specific area of the brain),
  • ataxia (inability to coordinate movements),
  • weakness
  • dementia Other problems may include hearing loss, eye problems, dysarthria (difficulty speaking), peripheral neuropathy (impaired sensation), short stature, exercise intolerance, lipomas (tumors of fat cells), and cardiomyopathy (heart muscle problems) with Wolf-Parkinson-White syndrome (heart conduction problems). The disease is variable in severity and features. Even within the same family, some people with the genetic change may have very few or no signs or symptoms, while others may have severe disease.

Possible Causes

Mitochondria are only inherited from our mothers. When mitochondria have a mutation, or genetic change, they do not produce enough energy for cells to function normally. If a woman has a mitochondrial disorder all of her children will be affected. Since all of a child’s mitochondria come from the mother, the disease cannot be inherited from an affected father.

Diagnosis

The diagnosis is made when a child has the following four features: myoclonus, generalized epilepsy, ataxia, and ragged-red fibers on muscle biopsy. Genetic testing is also available to look for the three most common mitochondrial DNA mutations in blood cells. These three mutations occur in 90% of affected patients. However, different parts of the body may have different amounts of DNA with a genetic change. In children with only mild symptoms, and in relatives without symptoms, the blood test may not detect the genetic change. In this case, other tissues are used such as skin, urine, cells obtained from mouthwash, hair, and most-reliably, muscle obtained by biopsy. Other tests used to make the diagnosis are elevated lactic acid in blood and spinal fluid, elevated protein in spinal fluid, abnormal electrical activity of the brain on EEG (electroencephalogram), abnormal electrical activity of the heart on ECG (electrocardiogram), abnormal electrical activity of nerves on EMG (electromyogram), and small size of the brain with abnormal calcifications on MRI (magnetic resonance imaging).

Treatment

Seizure medications are used to control the epilepsy component of the disease. However, no specific treatment for the mitochondrial gene mutation is currently available. Coenzyme Q10 and L-carnitine are often used in hopes of improving mitochondrial function, and thus improving energy level. Research is ongoing.

Prognosis

There is sometimes overlap with another syndrome, termed MELAS. In these cases, strokes can occur. In patients affected by MERRF, the disease can appear even as adults, and generally worsens with time. However, each patient is unique, and is variably affected by the disease.

Connect with other parents

In the spirit of community and support, Madisons Foundation offers the unique service of connecting parents of children with rare diseases. If you would like to be connected to other parents of children with this disease, please fill out this brief form.

Weblinks

Children’s Mitochondrial Disease Network
Copious information on mitochondrial diseases, links to related websites, a glossary of terms, and membership in the organization

CLIMB
Information, research studies, advice and support for families affected by metabolic diseases

Epilepsy Foundation
Sponsors conferences on seizure disorders and information about these illnesses

Muscular Dystrophy Association (MDA)
Contains an “Ask the Experts” section with questions from parents and answers from physicians. Also contains information on mitochondrial myopathies, summer camps, what to expect at clinic visits, and research. NIH/NINDS Brain Resources and Information

Network
Provides information on the various mitochondrial myopathies.

United Mitochondrial Disease Foundation
Provides information on mitochondrial diseases, conferences and research

Google Search for Myoclonic Epilepsy Associated with Ragged-Red Fibe

References and Sources

GeneReviews: www.geneclinics.org OMIM: www.ncbi.nlm.hih.gov National Organization for Rare Disorders (NORD): www.rarediseases.org