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MELAS syndrome

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Definition

noun

A multisystemic disorder characterized by mitochondrial myopathy, encephalopathy, lactacidosis, and stroke; an inherited disorder of the respiratory chain, either a deficiency of NADH:ubiquinone oxidoreductase (complex I of the chain) or of cytochrome c oxidase


Supplement

MELAS (i.e. an acronym for mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes) syndrome is a form of mitochondrial myopathy. A mitochondrial myopathy is a type of myopathy associated with mitochondrial dysfunction. One of the major distinctions of this condition is the inability of the muscle to perform properly. In mitochondrial myopathies, the underlying cause is a dysfunctional mitochondrion due to a pathological mutation in the mitochondrial DNA. In MELAS syndrome, the disorder is caused by either a deficiency of NADH:ubiquinone oxidoreductase (complex I of the chain) or of cytochrome c oxidase. The deficiency is caused by mutations in the mitochondrial DNA. In particular, mutations in the genes MT-ND1 and MT-ND5 may negatively affect the coding of proteins that make up NADH dehydrogenase (or complex I) in the mitochondria. This enzyme plays a part in the conversion of oxygen and simple carbohydrates to energy. Another possible genetic cause is mutation in the genes MT-TH, MT-TL1, and MT-TV. These genes normally code for transfer RNAs in the mitochondria. The most common genetic cause of MELAS syndrome is the mutation in the MT-TL1.

MELAS syndrome is typically inherited in a mitochondrial pattern. This means that the individual with this condition inherited the disorder from their carrier mother. This form of inheritance is referred to as maternal inheritance. This is because the egg cell is the source of the mitochondrial DNA.

MELAS syndrome is characterized by the following symptoms: encephalomyopathy, lactic acidosis, stroke-like episodes, endocrinopathy, diabetes, hearing loss, cardiovascular disease, short stature, and neurological manifestations.


Synonym(s):

  • mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS)
  • mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome

See also: