MELAS: a hereditary condition

MELAS is a rare condition in which organs in the body have difficulty functioning due to an energy shortage in the mitochondria. MELAS is one of the metabolic diseases. The disease is congenital and the first symptoms usually manifest between the ages of two and ten. The complaints occur equally in both sexes. The prevalence of this condition is one in 6250 in Europe.

  • What is MELAS?
  • Heredity
  • Symptoms of MELAS
  • Diagnosis
  • Treatment of MELAS
  • Prognosis for MELAS patients

What is MELAS?

The abbreviation MELAS means ‘Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-like Episodes’. MELAS is an inherited metabolic disorder. In this condition, the error is in the hereditary material in the mitochondria. Mitochondria are bean- or spherical cell organelles that function as the cells’ power plant. For that reason we can also call MELAS a mitochondrial disorder.

Mitochondrial dysfunction

Our body consists of many cells that have an important function in metabolism. A cell consists of a cell nucleus and various cell organelles. This includes the mitochondria. Metabolic processes take place in the mitochondria themselves. One of the most important functions of mitochondria is that it acts as a power plant of the cell. In MELAS patients, the function of mitochondria as a power plant is defective. The main cause of this dysfunction in MELAS patients is caused by a mutation in the mitochondrial mtDNA. Due to this error in the mitochondria, an important protein is not produced. This usually involves replacing one adenine molecule with a guanine molecule. This exchange causes the protein to malfunction and the mitochondria to function poorly, causing it to provide insufficient energy for the cell to function properly. This means that cells can die. The extent to which the disease progresses will also be more severe if more mitochondria are affected. In addition, the mitochondria in MELAS patients are much larger than normal, resulting in the wall of the small blood vessels in the body becoming thickened. This can cause cerebral infarctions. But MELAS affects many functions of the body.

Heredity

MELAS can only be inherited through the mother. The reason for this is that a fertilized egg cell only contains mitochondria from the cytoplasm of an egg cell. So children only inherit mitochondria from the mother. With MELAS, the abnormality is in the mitochondrial mtDNA of the egg cell. If the mother is a carrier of the error in the hereditary material, the mtDNA is randomly distributed among the cells of the fetus after fertilization. The mutation can therefore only come from the mother and can occur in both boys and girls. But since not all mitochondria contain the error and are randomly distributed among the different eggs, the chance of having a sick child can range from 0 to almost 100%. If the abnormality is prevented, again only girls can pass it on to their offspring.

Symptoms of MELAS

The symptoms are, on the one hand, the result of energy deficiency due to poor functioning of the mitochondria and, on the other hand, lactic acid is also formed. This means that the blood and tissues can become acidic. This can cause various organs to function poorly. The most common symptoms are the following:

  • Children have a short height
  • The children have little appetite
  • Epileptic seizures often occur
  • Headache attacks may occur
  • Vomiting attacks may occur
  • Children get tired more quickly
  • Muscle disease: staggering walking, double vision
  • Stroke-like episodes: Sudden onset of semi-paralysis with regular epileptic seizures. Difficulty speaking and seeing. After such an episode there is almost 100% recovery, but there are always residual symptoms that do not fully recover.
  • Developmental decline: children learn things they previously mastered.
  • Depression and psychoses during puberty
  • Hearing impairment and visual impairment
  • Problems with the nerves
  • Type II diabetes
  • Cardiac arrhythmias
  • Kidney problems
  • Gastrointestinal problems
  • Spots on the skin and increased hair

Diagnosis

Since the condition usually develops in childhood, the diagnosis will most often be made by a pediatrician or pediatric neurologist. A good diagnosis is very important here. Since the disease is rare, many doctors are not yet familiar with MELAS and it can lead to confusion in some cases. Many symptoms of MELAS also occur in other diseases. To arrive at a proper diagnosis, the following tests will need to be performed:

  • Stroke-like episodes are characteristic of MELAS patients.
  • Blood test: detection of increased lactate (lactic acid) in the blood and/or increased creatine kinase.
  • MRI scan: examination for the presence of cerebral infarctions.
  • Liquor examination: examination for increased lactate and protein content in the fluid.
  • Muscle biopsy: larger mitochondria and respond positively to staining with cytochrome c oxidase (COX).
  • ECG (ECG): detection of cardiac arrhythmias.
  • Genetic research: detecting errors in mitochondria.

Treatment of MELAS

MELAS cannot yet be cured. The treatment aims to relieve symptoms and guarantee patients a better quality of life. The treatment mainly consists of administering medication and follow-up by specialists.

  • Administering medication against epilepsy, migraine and diabetes.
  • Administering vitamin preparations, including coenzyme Q10, riboflavin, levocarnitine or idebedone.
  • Following a diet: it is important that the child gets all the healthy nutrients.
  • Physiotherapy, occupational therapy and rehabilitation: this can be very useful in the child’s muscle development.
  • Speech therapy: stimulating language is important in MELAS patients
  • Follow-up by an ENT doctor and ophthalmologist: Most MELAS patients have problems with hearing and vision.
  • Follow-up by a pediatric cardiologist and nephrologist: The heart and kidneys should be closely monitored.

Prognosis for MELAS patients

MELAS is a progressive condition in which symptoms will continue to increase. This means that patients suffer a gradual deterioration on both a physical and psychological level. Most patients with MELAS also eventually become demented. Children often die due to complications or secondary consequences. This is usually due to the disappearance of more and more vital functions. Most patients reach the age of between ten and forty years. Life expectancy has therefore been shortened, but reaching an older age is also possible.

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