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 (long-term), 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 and affect other diseases, including 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.

How common are mitochondrial diseases?

One in 5,000 individuals has a genetic 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) 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 his or her 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 the 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: In this unique type of inheritance, 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 disease.
  • Random mutations: Sometimes genes develop a mutation of their own that is not inherited from a parent.

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 differences in symptoms, severity, and age of onset (start of symptoms).

Symptoms of mitochondrial diseases can include:

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