Mitochondrial Myopathies

The mitochondrial myopathies are a group of neuromuscular diseases of the mitochondria. Mitochondria, which are small structures found in every cell in the body and are the "power plant" or energy-producing part of the cell, appear to cause the most damage in cells that require a great deal of energy such as nerves in the brain and muscles.

Some of the more common mitochondrial myopathies include Kearns-Sayre syndrome, oculocraniosomatic neuromuscular disease with ragged-red fibers, myoclonus epilepsy with ragged-red fibers (MERRF), and mitochondrial encephalomyopathy lactic acidosis and stroke-like episodes (MELAS).

The symptoms of mitochondrial myopathies include muscle weakness or exercise intolerance, heart failure or rhythm disturbances, dementia, movement disorders, stroke-like episodes, deafness, blindness, vomiting, and seizures.

These disorders range in severity from progressive weakness to death. The age of onset ranges from birth to adult life, with the majority of cases occurring before the age of 20. Exercise intolerance or muscle weakness usually develops by age 10. During activity, active muscles may become easily fatigued or weak. Nausea, headache and breathlessness are also sometimes associated.

There is no specific treatment for any of the mitochondrial myopathies. Occupational and physical therapies may extend the range of movement of muscles and improve dexterity. Vitamin therapies such as riboflavin, coenzyme Q, vitamins C and K, and carnitine (a specialized amino acid) may improve function in some patients.

The prognosis for mitochondrial myopathies varies greatly because progression of the disorders depends largely on the patient's metabolism, which is vastly different among individuals.

Information provided by the
National Institute of Neurological Disorders and Stroke,
National Institutes of Health

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.