What are mitochondria?

Mitochondria are the “energy factory” of our body. Several thousand mitochondria are in nearly every cell in the body. Their job is to process oxygen and convert substances from the foods we eat into energy. Mitochondria produce 90 percent of the energy our body needs to function.

Cell Diagram

What are mitochondrial diseases?

Mitochondrial diseases are chronic, genetic, often inherited disorders that occur when mitochondria fail to produce enough energy for the body to function properly. (Inherited means the disorder was passed on from parents to children.) Mitochondrial diseases can be present at birth, but can also occur at any age.

Mitochondrial diseases can affect almost any part of the body including the cells of the brain, nerves, muscles, kidneys, heart, liver, eyes, ears or pancreas.

Mitochondrial dysfunction occurs when the mitochondria do not work as well as they should due to another disease or condition. Many conditions can lead to secondary mitochondrial dysfunction including autism, Parkinson’s disease, Alzheimer’s disease, muscular dystrophy, Lou Gehrig’s disease, diabetes, and cancer. Individuals with secondary mitochondrial dysfunction do not have primary genetic mitochondrial disease and do not need to be concerned about the ongoing development or worsening of symptoms.

What are the symptoms of mitochondrial diseases?

Symptoms of mitochondrial diseases depend on which cells of the body are affected. Patients’ symptoms can range from mild to severe, involve one or more organs, and can occur at any age. Even patients within the same family who have the same mitochondrial disease can have different symptoms, vastly different severity of symptoms, and different ages of onset.

Symptoms can include:

How common are mitochondrial diseases?

One in 5,000 individuals has a mitochondrial disease. Each year, about 1,000 to 4,000 children in the United States are born with a mitochondrial disease. With the number and type of symptoms and organ systems involved, mitochondrial diseases are often mistaken for other, more common, diseases.

What causes mitochondrial disease?

In most people, primary mitochondrial disease is a genetic condition that can be inherited (passed from parents to their children).

Mitochondrial diseases can be inherited in several ways. To understand inheritance types, it’s helpful to learn more about genes and DNA. Genes are substances that give us our traits, such as brown eyes or blue eyes. Genes contain DNA, which is the ‘blueprint’ that gives each person their unique makeup.

Under normal circumstances, a child inherits genes in pairs -- one gene from the mother and one from the father. A child with a mitochondrial disease does NOT receive a normal pair of genes from their parents. The gene has mutated – meaning it has become defective (changed). Learning the way a mitochondrial disease has been inherited helps predict the chance of passing on the disease(s) to future children.

Inheritance types are:

Autosomal recessive inheritance. This child receives one mutated copy of a gene from each parent. There is a 25% chance that each child in the family will inherit a mitochondrial disease.

Autosomal dominant inheritance. This child receives one mutated copy of a gene from either parent. There is a 50% chance that each child in the family will inherit a mitochondrial disease.

Mitochondrial inheritance. This is a unique type of inheritance. In this type, the mitochondria contain their own DNA. Only mitochondrial disorders caused by mutations in the mitochondrial DNA are exclusively inherited from mothers. If this is the way a mitochondrial disease was inherited, there is a 100% chance that each child in the family will inherit a mitochondrial diseases(s).

Random mutations. Sometimes genes develop a mutation of their own that is not inherited from a parent.

How are mitochondrial diseases diagnosed?

Because mitochondrial diseases affect so many different organs and tissues of the body and patients have so many different symptoms, mitochondrial diseases can be difficult to diagnose. There is no single laboratory or diagnostic test that can confirm the diagnosis of a mitochondrial disease. This is why referral to a medical facility with physicians who specialize in these diseases is critical to making the diagnosis.

The first steps toward diagnosis start with a series of examinations and tests that may include:

Other tests, depending on the patient’s symptoms and the areas of the body that are affected, might include:

  • Magnetic resonance imaging (MRI) or spectroscopy (MRS) for neurological symptoms
  • Retinal exam or electroretinogram (ERG) for vision symptoms
  • Electrocardiogram (EKG) or echocardiogram for symptoms of heart disease
  • Audiogram or auditory-brainstem evoked responses (ABER) for hearing symptoms
  • Blood test to detect thyroid dysfunction if the patient has thyroid problems
  • Blood test to perform genetic DNA testing

More advanced testing could include biochemical testing, which looks for changes in body chemicals involved in energy making. Biopsies of skin and muscle tissue may also be performed.

How are mitochondrial diseases treated?

There are no cures for mitochondrial diseases, but treatment can help reduce symptoms or slow the decline in health.

Treatment varies from patient to patient and depends on the specific mitochondrial disease diagnosed and its severity. However, there is no way to predict patients’ response to treatment or predict how the disease will affect a person in the long run. No two people will respond to the same treatment in the same way, even if they have the same disease.

Treatments for mitochondrial disease may include:

--Vitamins and supplements including:

  • Coenzyme Q10
  • B complex vitamins, especially thiamine (B1) and riboflavin (B2),
  • Alpha lipoic acid
  • L-carnitine (Carnitor)
  • Creatine
  • L-Arginine

--Exercises. Both endurance exercises and resistance/strength training. These are done to increase muscle size and strength. Endurance exercises include walking, running, swimming, dancing, cycling and others. Resistance/strength training include such exercises such as sit-ups, arm curls, knee extensions, weight lifting and others.

--Conserve energy. Don’t try to do too much in a short period of time. Pace yourself.

--Other treatments may include speech therapy, physical therapy, respiratory therapy, and occupational therapy.

Avoid situations that can ‘trigger’ a worsening of your medical condition. Some triggers include: exposure to cold and/or heat; starvation; lack of sleep; stressful situations; and use of alcohol, cigarettes and monosodium glutamate. (MSG is a flavor enhancer commonly added to Chinese food, canned vegetables, soups and processed meats.)

What is the outlook (prognosis)?

That’s a difficult question to answer. The outlook depends on how many organ systems and tissues are affected and the severity of disease. Some affected children and adults live near normal lives. Others might experience drastic changes in their health over a very short amount of time. Some patients may experience flare-ups of their disease, then a return to a more stable state for years. Although there is no cure for mitochondrial diseases at the moment, research is ongoing.

Parents with mitochondrial disease(s) who are considering having other children may want to see a genetic counselor to discuss their concerns.

References

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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 10/9/2014...#15612