What is MELAS?
MELAS is a condition that causes a rare form of dementia. It falls under the umbrella term of ‘mitochondrial disease’. MELAS stands for:
- Mitochondrial myopathy – weakness of muscles throughout the body
- Encephalopathy – disease of the central nervous system
- Lactic Acidosis – abnormal build-up of lactic acid, normally a waste product, in the body
- Stroke – occurs when the blood supply to part of the brain is cut off by disease, and brain cells die.
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 our entire 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 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?
In many patients with MELAS, presentation occurs with the first stroke-like episode, usually when an individual is aged 4-15 years. Less often, onset of disease may occur in infancy with delayed developmental milestones and learning disability. One presentation of the disorder was reported in a 4-month-old infant.
How is MELAS treated?
Unfortunately there is as yet no treatment to stop the damage done by MELAS syndrome, and the outcome for individuals with the syndrome is usually poor. MELAS is progressive and patients are managed according to what areas of the body are affected at a particular time. In other words, treatment is tailored to the symptoms.
Moderate treadmill training can help improve the endurance of individuals with myopathy. Metabolic therapies, including dietary supplements, have shown benefits for some individuals. These treatments include coenzyme Q10, phylloquinone, menadione, ascorbate, riboflavin, nicotinamide, creatine monohydrate, idebenone, succinate, and dichloroacetate. Whether these supplements will help all individuals with MELAS syndrome is still being studied.
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.