Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-Like Episodes

What else is it called?

  • MELAS syndrome

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What causes it?

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes [MELAS syndrome] are mitochondrial pattern inherited disorders. In most cases, individuals diagnosed with this condition inherit a mutated gene from their mother, this is referred to as maternal inheritance. It is thought that this condition can be inherited from a number of genes, these genes are; MT-ND1, MT-ND5, MT-TH, MT-TL1, and MT-TV. These are found in the DNA of the mitochondria. The mitochondria are the energy producing centre of cells in the body. Although DNA is mostly packed in the chromosomes throughout the body, there is some DNA produced within the mitochondria, this is called mtDNA. mtDNA genes are usually lost in sperm cells during fertilisation, this is why this condition is mainly inherited by a maternal figure. The genes that are involved in MELAS syndrome usually provide instructions to make the proteins which break down fat and sugar within regions of the mitochondria. A mutation to these genes impairs the proteins functions and they cannot produce energy and oxygen as they usually would without one of the gene mutations. Research is still ongoing into how this condition impacts areas of the brain, also, current research does not explain how this condition is caused by these gene mutations.


How common is it?

The prevalence of MELAS syndrome is currently unknown, this is due to how rare it is. It is thought that this condition occurs in around 1 in 4000 individuals worldwide. It can be not said whether this condition is more common amongst males or females or within specific ethnicities.

What are the signs and symptoms?

MELAS symptoms mostly presents in childhood following a brief spell of normal childhood development. However, signs and symptoms can appear at any stage of life, but most commonly between the age of 2 and 15. Symptoms can vary per individual, some of the more common signs and symptoms which your child may experience are:

  • Seizures
  • Muscle weakness on one side of the body [hemiparesis]
  • Severe headaches resembling migraines
  • Repeated stroke like symptoms [occur before 40]
  • Problems with vision
  • Loss of intellectual function [Dementia]
  • Involuntary muscle spasms
  • Diabetes
  • Hormonal imbalances
  • Depression

Most people with this condition also have a build-up of lactic acid in the body, this is caused by a build-up of metabolites from the inability to break down fats and other products into energy and oxygen. This can lead to bouts of vomiting and sickness. Lactic acid can also accumulate within the spinal fluid which may cause damage to regions of the brain.


How is it diagnosed?

MELAS syndrome is usually diagnosed based upon genetic testing and physical and clinical symptoms of this condition. The mtDNA which is mutated with this condition can be found mostly in white blood cells, this can also be found in other tissues such as skin and hair follicles.

Muscle biopsy’s may be carried out to assert wastage of muscle tissue caused by MELAS syndrome. This involves taking a small piece of tissue from an area of muscle in your body to be tested.  Electrocardiograms can be carried out to look into heart abnormalities that may be apparent with this condition. An MRI may be carried out to look at areas of the brain that are impacted with this condition.

Can it be treated?

Treatment is mostly aimed at managing the symptoms as they present. Research persists into supplementing individuals with carnitine, ascorbic acid, riboflavin, creatine monohydrate and other medications. Coenzyme q10 and L-carnitine have been beneficial in some patients. Drugs can be prescribed to prevent episodes of seizures which may be experienced with this condition. Physical activity has shown to increase an individual’s aerobic capacity and has shown to reduce levels of lactate which can build up with this condition.

Do my family need to be tested?

MELAS syndrome is inherited by defects in the genome of the mitochondria, these genes found in the mitochondria are collectively known as mitochondrial DNA [mtDNA]. Mitochondrial DNA are structures which provide instructions to break down or convert molecules into energy. Because only the female egg contributes to the development of these mitochondria DNA’s, these can only be passed on by the female to their offspring, this is otherwise known as maternal inheritance. This type of inheritance pattern will never be passed on by males.

Relevant Organisations


References are available on request. Please contact Helen Morris by phoning 0845 241 2173 or emailing [Resource Library No: AAP002].

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