What is MELAS?
What causes MELAS?
MELAS syndrome 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, some of our DNA is in another important structure called the mitochondrion (plural: mitochondria).
The mitochondria are 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 all of our mitochondrial chromosome from our mother.
Much of the DNA in our mitochondria is used to manufacture proteins involved in the key function of mitochondria -- to produce energy and power the cells in our body.
What are the symptoms of MELAS?
As a result of the disturbed function of their cells' mitochondria, patients with MELAS develop
How is MELAS diagnosed?
The diagnosis of MELAS is usually suspected on clinical grounds. However, confirmation of the diagnosis usually requires a muscle or brain biopsy. The muscle biopsy shows characteristic ragged red fibers; a brain biopsy shows stroke-like changes.
How is MELAS treated?
There is no known treatment for the underlying disease, which is progressive and fatal. Patients are managed according to what areas of the body are affected at a particular time. antioxidants and vitamins have been used, but there have been no consistent successes reported.
Are there other mitochondrial diseases?
Yes, mutations (genetic changes) in the mitochondrial chromosome are responsible for a number of other disorders aside from MELAS such as:
- an important eye disease called Leber hereditary optic atrophy;
- a type of epilepsy called MERRF which stands for Myoclonus Epilepsy with Ragged Red Fibers; and
- a neuromuscular disease called the Kearns-Sayre syndrome.
MELAS and all other mitochondrial diseases were not well understood before it was discovered that they were due to mutations in the chromosomes of the mitochondria.
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"Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes"
National Institutes of Health