Mitochondrial Disorders

Mitochondrial Disorders

Mitochondrial Disorders - inherited mutations in mitochondrial genes that result in functional disturbances in various body systems. Mitochondria are structures within the cell that generate the energy, in the form of adenosine triphosphate (ATP), the cell requires to function. A cell may contain dozens of mitochondria. Each mitochondrion contains the specific genetic material (MITOCHONDRIAL DNA [MTDNA]) to encode the enzymes (specialized proteins) that regulate the biochemical reactions within the mitochondrion that generate ATP. The only function of mtDNA is to regulate these processes of energy production.

Each mitochondrion contains multiple copies of its DNA. Mutations typically affect some but not all DNA copies, so mitochondrial function continues though may be impaired whenever the mutated mitochondrial GENE sends incorrect code. Only the ovum contains mitochondria that pass on to the ZYGOTE at CONCEPTION. SPERM cells contain few mitochondria, and these are in the sperm cell’s tail, which breaks away as soon as the sperm penetrates the ovum. As the zygote continues to divide, it may perpetuate errors in mtDNA that are widespread or pervasive.

Mitochondrial disorders include myositis, some types of CARDIOMYOPATHY, some types of MYOPATHY, and carnitine deficiency syndrome. Often, symptoms are multisystem and inconsistent with the conventional presentations of the health conditions they suggest. MUSCLE and NERVE cells have particularly high energy needs, so mitochondrial disorders often manifest symptoms such as weakness and poor muscle tone (hypotonia).

Because mitochondrial disorders are rare and their symptoms are confusing, the diagnostic path may lead to numerous dead ends. Though this process rules out other diagnoses, it is a frustrating experience for those patients looking for answers for their symptoms. There are no definitive diagnostic tests for mitochondrial disorders, though muscle biopsy often can provide strong evidence supporting diagnosis once doctors rule out other conditions and disorders. Treatment targets managing symptoms and preventing common complications such as DEHYDRATION. Some doctors advocate COENZYME Q10 supplementation for people who have mitochondrial disorders, which appears to improve the efficiency of cellular METABOLISM as well as protect cells from oxidative damage. People who have mitochondrial disorders should include GENETIC COUNSELING in their FAMILY PLANNING efforts.

See also CELL STRUCTURE AND FUNCTION; CHROMOSOME DISORDERS; GENETIC DISORDERS; MUTATION; REPLICATION ERROR.

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Genetics and Molecular Medicine

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