All mitochondrial diseases are known by acronym abbreviations (e.g., MELAS, MERRF, NARP, LHON).
Acronyms were commonly used when these disorders were first described. Today, the naming of mitochondrial disorders is evolving. Mitochondrial disorders are currently named by any of the following methods:
- By acronym descriptions (still in use although most people with a mitochondrial disorder do not have an "acronymic-named" disorder)
- By a name based on a person who described the disease
- By a name based on a specific genetic mutation
- By a name based on a microscopic description of tissue, or
- By a name based on the deficient enzyme
It is important to note that the labels given this disorder do not, in and of themselves, predict the long-term outcome or alter treatment.
Mitochondrial diseases are inherited only from your mother.
The current thinking is that most mitochondrial diseases are the result of one or more complex inheritance patterns. Most mitochondrial diseases are the result of mutations (changes) in DNA located in the nucleus of the cell. Only mitochondrial disorders caused by mutations in the mitochondrial DNA (a specific structure in living cells, located outside the nucleus) are inherited exclusively from mothers.
Another source of mitochondrial disorders that affects a large percentage of patients is poorly functioning mitochondria that become that way because of:
- another disease process (including other chromosomal disorders)
- exposure to toxins or viruses
- other inherited genetic mutations that are not disease-causing until "triggered" by some other genetic factor
Mitochondrial disease is a childhood disease.
Although mitochondrial disorders are commonly seen in infants and children, they can occur at any age.
An individual with mitochondrial disease has mental retardation, growth problems, and/or seizures.
Only some individuals have these developmental problems. Patients' symptoms can range from extremely mild to severe, can involve one or more body systems, and can emerge at any age. The brain, muscles, heart, liver, nerves, eyes, ears, and kidneys are the organs and tissues most affected. Most patients' symptoms fluctuate over the course of their illness -- patients at some times experience no or few symptoms, and at other times have many and/or severe symptoms. Even family members with the same disorder can experience vastly different symptoms.
Since mitochondrial diseases are incurable, no treatments can be given to these patients.
Even though these disorders are long term and incurable, treatments are available. Early treatment of symptoms can reduce their impact and limit further disability. Avoiding certain medications and stressful situations that worsen symptoms is also helpful. Certain medications and supplements may improve mitochondrial disease-related symptoms -- just as they do for other incurable diseases -- such as diabetes and emphysema.
Patients with mitochondrial disease all have elevated lactic acid levels in their blood.
An elevated lactic acid level, along with other symptoms, typically does indicate a mitochondrial problem and requires further investigation. However, elevated lactic acid levels are not seen in all types of mitochondrial diseases. In making the diagnosis, your doctor will look for other signs of mitochondrial disorders in blood, urine, and spinal fluid samples.
A muscle biopsy is the "gold standard" for diagnosis of mitochondrial disease.
Although the muscle biopsy is a powerful diagnostic tool, it should not be considered a "gold standard." Examination of a biopsy includes microscopic evaluation, enzyme testing, and genetic testing. Although all U.S. labs that offer muscle biopsy meet strict laboratory guidelines, there is no agreed-upon standard approach for enzyme testing. Furthermore, a muscle biopsy with full analysis costs well over $10,000 and poses both surgical and anesthetic risks. In some patients, the diagnosis can be made based on clinical symptoms and a positive blood test (identifying a genetic mutation) or a combination of clinical findings and other non-invasive testing -- in either case, a muscle biopsy is not necessary. Finally, since biopsy results usually do not alter the long-term outcome or treatment considerations, some specialists and patients choose to treat without the need for a muscle biopsy.
A muscle biopsy is a muscle biopsy no matter where and how it is done.
Muscle removed for biopsy can be tested in many ways. For example, enzyme testing can be done on either ground-up muscle or on mitochondria extracted from muscle. Testing on extracted mitochondria is performed in only a few medical center laboratories and must be performed immediately. This procedure is known as a "fresh biopsy." In an alternative procedure, called a "frozen biopsy," the muscle is quickly cooled and stored at -80 degrees Celsius for testing at an outside facility. The scientific community is currently debating the advantages of testing "fresh vs. frozen" mitochondria. Some evidence indicates that the "fresh biopsy" may be the superior method. Other types of mitochondrial testing of the muscle biopsy may need to be conducted; a limited number of laboratories offer such testing.
For additional information on mitochondrial diseases, contact:
The United Mitochondrial Disease Foundation
8085 Saltsburg Road, Suite 201
Pittsburgh, PA 15239
The Mitochondrial Medicine Society
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 2/12/2010...#13143