Mitochondria are structures that are found within the cells of your body. Their main function is to use oxygen, sugars, and ketones to make the energy that your cells need to function. Think of them as little power plants in your cells.

Sometimes, mitochondria don’t work effectively. When this happens, it means that your cells don’t have enough energy to work properly. This is called mitochondrial disease.

Below, we’ll dive deeply into mitochondrial disease, what causes it, how it’s diagnosed, and its overall outlook. Continue reading to learn more.

In mitochondrial disease, mitochondria are inefficient at generating energy or do not generate energy at all. Because of this, the organs and tissues that are impacted may not function properly.

A 2022 study notes older research which found that mitochondrial disease is estimated to impact 1 in 4,000 people in the United States and 1 in 5,000 people globally. This study found a similar prevalence in Canada as well.

Primary vs. secondary mitochondrial disease

There are two general types of mitochondrial disease: primary and secondary.

Primary mitochondrial disease

Primary mitochondrial disease happens due to DNA mutations that are inherited from one or both of your parents. These mutations impact the process through which the mitochondria make energy for your cells.

Some people with primary mitochondrial disease have defined groups of mutations and symptoms which are classified as specific syndromes. Some examples include Leigh syndrome, Kearns-Sayre syndrome, and MELAS.

Secondary mitochondrial disease

Secondary mitochondrial disease is due to mutations that don’t directly affect the energy generation pathway but still impact the function of mitochondria in some way. These types of mutations are typically inherited but can be acquired.

Mitochondrial disease can come on at any age. While many types of mitochondrial disease occur during childhood or adolescence, it’s also possible to develop symptoms as an adult.

Speaking of symptoms, there’s a huge variety of symptoms that can happen in mitochondrial disease. This is because the type of symptoms a person experiences depends on the number and type of cells that are affected.

Based on this, there are also large variations in symptom severity. Some people with mitochondrial disease may have few noticeable symptoms while others may have severe, debilitating disease.

The symptoms of mitochondrial disease are often most noticeable in parts of the body that use the most energy. These include the brain and nervous system, muscles, and heart. Symptoms can impact one or many areas of the body.

The table below shows some of the potential symptoms of mitochondrial disease based on the area of the body that’s impacted.

Potential symptoms of mitochondrial disease

Primary mitochondrial disease happens due to inherited DNA mutations that affect the energy-producing processes used by mitochondria. Two types of DNA can be involved:

  • Mitochondrial DNA (mtDNA): mtDNA is DNA that’s found within the mitochondria. Typically, a certain threshold of mtDNA needs to mutate within a cell in order for the energy production process to be affected.
  • Nuclear DNA (nDNA): nDNA is found within the nucleus of the cell. This is the type of DNA that you’re probably familiar with.

Secondary mitochondrial disease happens due to mutations in other genes that can impact the function of mitochondria. These mutations are often inherited as well.

Some inherited conditions are associated with secondary mitochondrial disease, such as:

Mutations in secondary mitochondrial disease can also happen due to other factors. These include things like:

  • the natural aging process
  • inflammation
  • exposure to toxins

Lastly, other health conditions can also result in impaired mitochondrial function. These are not caused by a genetic factor and can include:

Mitochondrial disease is very challenging to diagnose. That’s because of the large diversity in the types of mutations involved and the symptoms they may cause.

Additionally, many of the symptoms caused by mitochondrial disease may be caused by other, more common conditions. As such, a doctor must work carefully to rule out other conditions first.

A 2018 study explored the challenges associated with receiving a diagnosis of mitochondrial disease. It surveyed 210 people who had been diagnosed with mitochondrial disease and found that:

  • On average, people visited eight different medical professionals prior to receiving their diagnosis.
  • A majority of people, 54.6%, received one or more diagnoses other than mitochondrial disease before their final diagnosis.

The diagnostic process begins with a physical exam and a thorough personal and family medical history. A variety of tests are also used. Let’s explore these now.

Laboratory tests

A doctor will use a variety of tests to evaluate markers of how well the mitochondria are functioning. This can involve a variety of samples, including:

The types of markers examined by these tests are associated with the energy production processes of the cells in your body, and may include:

  • lactate and pyruvate
  • certain amino acids, such as proline and alanine
  • carnitine
  • organic acids in urine

DNA testing

Because mitochondrial disease happens due to mutations in DNA, a doctor will order DNA testing if they suspect mitochondrial disease.

DNA testing often involves looking for mutations in mtDNA. However, panels to detect mitochondrial disease-associated mutations in nDNA are also available as well.

These tests can typically be done using a blood sample. However, to help make a diagnosis, mtDNA in another type of sample may be analyzed as well.

When necessary, this is typically done using a sample of skeletal muscle. The benefit to using this tissue type is that it needs a high amount of energy to function properly and, as such, its cells contain high numbers of mitochondria.

Tissue testing

When other tests for mitochondrial disease don’t help with a diagnosis, tissue testing may be recommended. This uses a sample of tissue from one of your skeletal muscles.

Once the sample is collected, a variety of tests are done to see how well different steps of the energy production process are working. The results can inform your doctor about which step (or steps) in this complex process is impacted.

Other tests

A doctor may also use other tests to help them make a diagnosis, such as:

  • Imaging: Imaging technology, such as MRI or CT scans, can give a doctor a better look at the structure of the brain and surrounding tissues.
  • Neurological tests: Neurological tests can provide information on what’s happening in the brain. For example, an electroencephalogram shows electrical activity in the brain, while magnetic resonance spectroscopy records biochemical changes in the brain.
  • Muscle tests: Electromyography and nerve conduction tests can help to assess muscle function and the nerve signaling involved.
  • Cardiac tests: Tests like an electrocardiogram and an echocardiogram can help look for problems with the heart.
  • Blood tests: Blood tests can detect low blood sugar and thyroid problems, which can sometimes happen in mitochondrial disease.
  • Hearing and vision tests: Mitochondrial disease can also impact hearing and vision, so you may be tested for hearing loss or vision changes as a part of your diagnosis.

Mitochondrial disease often happens due to inherited mutations. In this situation, it’s not possible to prevent it.

If you or a close relative have mitochondrial disease, it may be helpful to meet with a genetic counselor. Based on your individual situation, they can help to give you a better idea of the risk of future children having the condition as well.

Some mutations in secondary mitochondrial disease may happen due to other factors like inflammation and toxins. As such, you may try to:

It’s important to note that there’s no direct evidence to show that doing these things prevents mitochondrial disease. However, all of the tips above are vital parts of promoting a healthy lifestyle.

Many of the mutations that cause mitochondrial disease are inherited. As such, if you have a close family member that has mitochondrial disease, you may be at an increased risk. Close family members include parents, siblings, and children.

Additionally, some mutations that contribute to mitochondrial disease may be acquired during a person’s lifetime. While research is scarce, risk factors for these types of mutations may include:

  • older age
  • certain health conditions
  • exposure to toxins in the environment

There’s currently no cure for mitochondrial disease. Doctors and scientists continue to do research to find effective ways to treat this condition.

Currently, the treatment of mitochondrial disease focuses on relieving symptoms and improving quality of life. This is called supportive care. Potential supportive care options include things like:

  • taking supplements like coenzyme Q10, thiamine, and riboflavin
  • eating a special diet developed in cooperation with your care team
  • engaging in moderate levels of exercise
  • using assistive devices, if necessary
  • participating in physical, occupational, or speech/language therapy, if needed

In some cases, mitochondrial disease can be a progressive condition. That means that it gets worse as time passes.

However, every person with mitochondrial disease is different and outlook can depend on which parts of the body are affected. Your care team can help to give you a better idea of what your individual outlook is like.

Now let’s look at some answers to other questions you may have about mitochondrial disease.

How is mitochondrial disease inherited?

The answer to this question depends on where the mutations are present. Mutations in nDNA can be inherited from one or both of your parents.

Mutations in mtDNA are inherited from your mother. This is because at fertilization, the egg contains more mitochondria than the sperm, which also breaks down after it has fertilized the egg.

Are there any medications people with mitochondrial disease should avoid?

Yes, some medications can affect mitochondrial disease. A few examples include, but aren’t limited to:

If you have mitochondrial disease and need to take a new medication, ask your doctor about how it may affect your condition. It’s possible that you may need additional monitoring while you’re on the medication.

How does COVID-19 affect mitochondrial disease?

Infections stress your body’s metabolic system as your body works hard to cope with them. Because of this, they may worsen mitochondrial disease or cause it to progress.

A 2022 study of 79 people with primary mitochondrial disease and COVID-19 found that:

  • Out of all of the participants, 32% were hospitalized. Having respiratory problems due to mitochondrial disease was associated with an increased risk of COVID-19 hospitalization.
  • Most people (61%) recovered completely from COVID-19.
  • Another 35% recovered with persistent problems like worsening neurologic symptoms and lasting fatigue.
  • Only a small percentage of people (4%) died due to COVID-19.

Do vaccines worsen mitochondrial disease?

According to the Centers for Disease Control and Prevention (CDC), there’s currently no evidence that vaccines worsen mitochondrial disease. However, vaccines can prevent infections that can make mitochondrial disease worse.

Mitochondria supply your cells with vital energy. In mitochondrial disease, the mitochondria don’t work well or don’t work at all.

Mitochondrial disease is caused by mutations that directly or indirectly affect how mitochondria work. While many of these mutations are inherited, some can be acquired.

Because mitochondrial disease can happen due to a wide variety of mutations and can lead to a variety of symptoms, it can be difficult to diagnose. You may need to meet with several medical professionals before getting a diagnosis.

Mitochondrial disease has no cure yet. Outlook also varies greatly from person to person. If you have mitochondrial disease, be sure to discuss your individual outlook with your care team.