Definition of MELAS syndrome
MELAS syndrome: MELAS is
the acronym for Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like episodes.
MELAS is a rare form of dementia.
It is caused by mutations in the genetic material (DNA) in the mitochondria. While most of
our DNA is in the chromosomes in the cell nucleus, another important cell structure that carries
DNA is the mitochondrion. Much of the DNA within the mitochondrion is used to manufacture proteins
that help in the mitochondrion's energy-producing function.
As a result of the disturbed function of their cells'
mitochondria, patients with MELAS develop brain dysfunction
(encephalopathy) with seizures and headaches, as well as muscle
disease with a buildup of lactic acid in the blood (lactic acidosis), temporary local paralysis
(stroke-like episodes), and abnormal thinking (dementia).
MELAS is diagnosed by muscle biopsy showing characteristic ragged red fibers. Brain biopsy shows
stroke-like changes.
MELAS affects persons at different times of life, from 4 to 40s. Most patients show symptoms before
20 years old.
Patients are managed according to which areas of the body are affected at a particular time. There
is no known treatment for MELAS which is progressive and fatal.
Mutations (changes) in the mitochondrial chromosome are responsible for a number of disorders
including not only MELAS but also for examples:
- An eye disease called Leber's hereditary optic atrophy; and
- A type of epilepsy called MERRF which
stands for Myoclonus Epilepsy with Ragged Red Fibers.
The mitochondria, as mentioned, are normal structures located outside the nucleus in the cell's cytoplasm. Each mitochondrion has a chromosome made of DNA that is quite different from the better known chromosomes in the nucleus. The mitochondrial chromosome is much smaller; it is round (whereas the chromosomes in the nucleus are normally shaped like rods); there are many copies of the mitochondrial chromosome in every cell; and no matter whether we
are male or female, we inherit our mitochondrial chromosome from our mother.
MELAS and all other mitochondrial diseases were entirely enigmatic before it was discovered
that they were due to mutations not in regular chromosomes but in the chromosome of mitochondria.
Last Editorial Review: 3/26/1999 3:10:00 PMCommon Misspellings: melas syndrone
- Stroke - Learn about strokes symtoms like sudden numbness or weakness in the face, arms, or legs, confusion, vision problems, problems with walking or coordination, or severe headache.
- Dementia - Learn about the types of dementia, and what causes it, the symptoms, diagnosis, treatment and prevention of this progressive disease.
- Seizure (Epilepsy) - Learn about epilepsy, or seizure disorder. Causes include head injury, trauma, prenatal injury, poisoning, medications, stroke, heart attacks, alcoholism, infection, and more. Symptoms, diagnosis, and treatment information is included in the information.
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