melas syndrome
MELAS Syndrome
Medical Author: |William C. Shiel, Jr., MD, FACP, FACR|
Medical Editor: |Frederick Hecht, M.D., F.A.A.P., F.A.C.M.G.|
- |What is MELAS?|
- |What causes MELAS?|
- |What are the symptoms of MELAS?|
- |How is MELAS diagnosed?|
- |When do people with MELAS develop symptoms?|
- |How is MELAS treated?|
- |Are there other mitochondrial diseases?|
|What is MELAS?|
|MELAS| is a rare form of |dementia|. MELAS is an abbreviation that stands for |Mitochondrial Encephalopathy|, Lactic Acidosis, and Stroke-like episodes.
|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.
In this Article
- |What is MELAS?|
- |What causes MELAS?|
- What are the symptoms of MELAS?
- How is MELAS diagnosed?
- When do people with MELAS develop symptoms?
- How is MELAS treated?
- Are there other mitochondrial diseases?
- |MELAS Syndrome Glossary|
- |MELAS Syndrome Index|
|What are the symptoms of MELAS?|
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 build-up of lactic acid in the |blood| (a condition called |lactic acidosis|), temporary local paralysis (stroke-like episodes), and abnormal thinking (dementia).
|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.
|When do people with MELAS develop symptoms?|
MELAS can affect people at very different times in life, ranging from age 4 to age 40 or more. However, most patients with MELAS syndrome show symptoms before they are 20 years old.
|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 entirely enigmatic before it was discovered that they were due to mutations not in regular chromosomes but in the chromosome of the mitochondria.
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