Topic Overview

What are mitochondrial diseases?

Mitochondria (say "my-tuh-KAWN-dree-uh") are tiny parts of the cells in your body. Mitochondria are often called the powerhouse of a cell, because one of their jobs is to make energy.

Mitochondrial diseases are a group of rare diseases that can be passed down from mothers to their children. The diseases happen when mitochondria don't work the way they should.

These diseases can appear at any age. And they can affect many different areas of the body.

Examples of these diseases include:

• Kearnes-Sayre syndrome. Symptoms usually appear before the age of 20 and affect the eyes and ears.
• Leigh syndrome. It affects a baby's nervous system. It usually begins in the first year of life.
• MERRF syndrome. MERRF affects the nervous system, muscles, and other areas of the body.
• MELAS syndrome. MELAS affects many areas of the body, including the brain, nervous system, and muscles.

What are the symptoms?

The symptoms depend on the type of cells that have damaged mitochondria. Symptoms can vary from person to person.

Mitochondrial disease in brain cells can cause symptoms such as:

• Dementia.
• Seizures.
• Strokes.

When the disease is in muscle cells, the symptoms can include:

• Weakness.
• Cramps.
• Problems with movement.

In the cells of the ears or eyes, mitochondrial diseases can cause:

• Deafness.
• Blindness.
• Droopy eyelids.
• Problems with eye movement.

Other parts of the body that may be affected include the kidneys, nerves, or liver.

How are mitochondrial diseases diagnosed?

If you or your doctor thinks that you have a mitochondrial disease, your doctor will do a physical examination and medical tests. Your doctor will ask questions about you and your health. He or she will also ask about your family's health to find out if anyone else in your family has similar symptoms.

The kind of medical tests you get will depend on your symptoms and on which parts of your body are affected. Tests that may be done include a muscle biopsy and imaging tests like an MRI. Your doctor may also want you to have a genetic test.

Your doctor may suggest that you see a genetic counsellor. These counsellors are trained to explain the genetic test and its results, but you make the decision about whether to have the test. They also provide education and support to families with members who have birth defects or genetic conditions like mitochondrial diseases. Genetic counselling can help you understand your risk of having a child with mitochondrial disease.

How are they treated?

Treatment usually focuses on relieving your symptoms and helping you feel better. You and your doctor will work together to find the treatment that works best for you. Treatment may include:

• Getting physiotherapy.
• Eating healthy foods.
• Getting enough rest.
• Avoiding people who are sick.
• Staying at a comfortable temperature.

Your doctor also may recommend taking certain vitamins and natural health products.

Surgery or other procedures may be recommended for physical symptoms like drooping eyelids, cataracts, or hearing loss.