Mitochondrial Diseases

Our bodies are made up of billions of small units called cells. Mitochondria (my-toe-kon-dree-uh) are tiny structures within cells that make energy for our bodies to use.  Mitochondria make more than 90 percent of the energy we need to live.  There are hundreds to thousands of mitochondria in each cell.

Mitochondrial diseases are caused by mitochondria not working properly. When mitochondria are not working well, the cell does not have enough energy and may be injured or die.  When many cells of the body do not have enough energy, whole organ systems (such as the nervous system or the digestive system) can be affected.

There are many types of mitochondrial diseases. Some mitochondrial diseases are mild and cause only a few symptoms. Others are serious and can affect many parts of the body. Many mitochondrial disorders are progressive, meaning that symptoms tend to get worse with time.

Mitochondrial diseases are caused by changes, or “mutations,” in genetic information (DNA).  DNA is like the instruction manual that tells our bodies how to grow and develop. Cells have two types of DNA.  Most DNA is found in the innermost part of the cell, called the nucleus, and is called nuclear DNA (nDNA).  A much smaller amount of DNA is found in the mitochondria and is called mitochondrial DNA (mtDNA). 

Changes in nuclear DNA and mitochondrial DNA can cause mitochondrial disease. These changes can either be passed down in a family (inherited), or they can be new in a person’s DNA.  Mutations are random; people cannot do anything to cause them or to stop them from happening.

The organs of our body use different amounts of energy. Mitochondrial diseases cause the most damage to organs that use the most energy.  The brain, heart, liver, muscles and kidneys all have large energy needs.  The endocrine (hormone-making) and respiratory (breathing) systems can also be affected. 

Symptoms of a mitochondrial disorder can show up in childhood or later in life.  Symptoms can be different for each person. These signs often overlap with many common conditions.  Different mitochondrial disorders can be hard to tell apart, and two people with the same disorder may have very different symptoms. 

Symptoms of a mitochondrial disorder can include: 

  • Muscle pain and weakness
  • Poor control over limbs
  • Poor growth
  • Heart disease
  • Liver disease
  • Diabetes
  • Seizures
  • Problems breathing and swallowing
  • Digestive issues
  • Vision and hearing problems
  • Developmental delay 

There are currently no cures for mitochondrial diseases. Treatments cannot fix organ damage already caused by the disease.  The purpose of treatment is to try to reduce symptoms and to keep the disease from becoming worse. Treatments may not work for all patients, depending on how severe the patient’s symptoms are and the specific disorder.   

Some treatments such as vitamins and cofactors (chemicals that help proteins do their job) are useful for some patients.  Therapies such as physical or occupational therapy, speech therapy or respiratory therapy may also be helpful for some people.  There are also several clinical trials in progress that may help some patients.


Last Updated 11/2012