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Common causes of complex disorders.

Increasingly, mitochondrial diseases are recognized as a relatively common cause of degenerative diseases in both children and adults. While the role of mitochondria as the power plants of the cell has been understood at the biochemical level for decades, the role of mitochondrial defects in human disease has only recently been recognized. The delay in recognizing the importance of mitochondrial diseases is the result of their variable and complex signs and symptoms as well as the novel genetics and atypical inheritance of mitochondrial defects.

The mitochondria generate energy by breaking down carbohydrates and fats through a chain of chemical reactions. Since each organ in the body relies on mitochondrial energy to a different extent, the nature and severity of symptoms vary widely in patients, depending on the specific mutations in their nuclear and mitochondrial genes. Indeed, since the percentage of mutant mitochondrial DNAs (see Glossary on page 50) can differ among individuals in the same family and even among tissues of the same individual, the same mitochondrial DNA mutation can cause different symptoms even in members of the same family.

Though all tissues make and need mitochondrial energy, the areas of the body that are most reliant on mitochondrial energy are the central nervous system (brain and spinal cord), heart, skeletal muscle, endocrine systems (glands like the thyroid and pancreas) and kidneys. By their effects on these areas, mitochondrial diseases can cause certain forms of blindness, deafness, dementia, movement disorders, epilepsies, seizures, heart disease, muscle disease, diabetes and kidney problems.

Moreover, depending on the gene involved and the severity of the mutation, mitochondrial diseases can affect people of all; ages, from newborns through adulthood. Well-known mitochondrial diseases of children are Leigh's syndrome, cardiomyopathty, and medium-chain acyl CoA dehydrogenase (MCAD) deficiency Typical mitochondrial diseases of young adults include Leber's hereditary optic neuropathy and Kearns-Sayre syndrome. Mitochondrial defects have also been implicated in more common diseases such as diabetes, dystonia, and Altheimer's disease. (See TABLE 2, PG. 42). In fact, it has been suggested that mitochondrial DNA mutations accumulate with age in the different tissues of our bodies, progressively eroding energy production, and playing an important role in the progression of degenerative diseases and in aging.

[TABULAR DATA 2 NOT REPRODUCIBLE IN ASCII]

Mitochondrial diseases, while only lately identified, are not rare. They may be an important component of some of the most common degenerative problems which plague our society. It is vital that this important new mechanism for disease be actively investigated and understood so that mitochondrial disorders can be routinely considered when diagnosing acute diseases of the newborn as well as the progressive disorders of aging.
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Title Annotation:Mitochondrial/Metabolic Disorders, part 1; Mitochondrial Diseases; includes glossary, directory of support organizations, questions to ask your doctor
Author:Wallace, Douglas C.
Publication:The Exceptional Parent
Date:Jun 1, 1997
Words:436
Previous Article:Time for us.
Next Article:The spectrum of mitochondrial disease.
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