Mitochondria are responsible for producing and providing energy to our bodies, especially in organs such as the heart, brain, and muscles, which require high-energy production. These organs consequently, require more mitochondria than other body areas to function properly.
Unfortunately, sometimes, the mitochondria in our bodies fail to produce enough energy for our bodies to function properly. Mitochondrial diseases are long-term (i.e., chronic) diseases usually inherited from our parents. While these diseases can manifest at birth, sometimes, they don’t develop until later in our life.
What Are Mitochondria?
Thousands upon thousands of mitochondria exist inside each cell in our body. Essentially, these mitochondria function as an energy factory, supplying our body with 90% of the energy we require to operate. To do this, the mitochondria work to process oxygen and change material from the food we eat into energy.
Where Are Mitochondria Found?
Mitochondria accompany other organelles and can be found in the cytoplasm: the liquid filling of a cell. Only a few cells in the body do not possess mitochondria. Most of our cells house these organelles. However, the number of mitochondria found in a cell depends on the function of that cell. For example, high-energy organs such as the heart will require more mitochondria than other organs.
Mitochondria Parts
Mitochondria are oblong organelles and can vary in length between 1 micrometer and 10 micrometers. Each mitochondrion has five primary parts:
- Outer Mitochondrial Membrane
- Inner Mitochondrial Membrane
- Intermembrane Space
- Cristae: Folds of the inner membrane
- Mitochondrial Matrix: The central cavity. It houses enzymes, as well as ribosomes, which help facilitate protein synthesis.
Mitochondrial Diseases
Mitochondrial diseases are chronic, meaning that once manifested, they are present for the rest of your life. In addition to being chronic, mitochondrial diseases are also usually passed from parent to child.
These diseases can occur in many areas of the body—in fact, most body parts can be affected by mitochondrial diseases, including the brain, kidneys, liver, heart, and other body parts.
Mitochondria diseases often occur when the mitochondria don’t function as they should. Sometimes these diseases are due to an underlying disease or condition such as Alzheimer’s, muscular dystrophy, Lou Gehrig’s disease, diabetes, and cancer.
Are Mitochondrial Diseases Common?
Genetic mitochondrial disease accounts for most cases. In fact, an estimated one in 5,000 people have genetic mitochondrial disease, and an estimated 1,000 to 4,000 children in the United States are born with a mitochondrial disease yearly.
Sometimes, though, mitochondrial diseases are mistaken for other more common diseases, especially since a wide variety of types and organs are involved. This makes the exact number of cases unknown.
What Causes Mitochondrial Disease?
Genetics are a huge factor in mitochondrial diseases. In most cases, a child inherits a mitochondrial disease from their parents. This can happen in several different ways:
- Autosomal recessive inheritance: A child obtains a single mutated gene from each parent. This results in a 25% chance of each child born in the family inheriting the mitochondrial disease.
- Autosomal dominant inheritance: A child obtains a single mutated gene from one parent. In cases of autosomal dominant inheritance, there is a 50% chance that each child in the family will develop the mitochondrial disease.
- Mitochondrial inheritance: In cases of mitochondrial inheritance, there is a 100% chance that all children in the family will inherit a mitochondrial disease. This is a rare type of inheritance where familial mitochondria possess unique DNA.
- Random mutations: In rare cases, genes may develop mutations on their own, unrelated to the parents. This means that a child may develop a mitochondrial disease that is not inherited.
Mitochondrial Diseases Symptoms
Symptoms will vary depending on the organs and cells affected. Additionally, symptoms can range from mild to severe and can occur at any age.
Some symptoms of mitochondrial disease include:
- Stunted growth
- Weak muscles and exercise intolerance
- Problems with vision and/or hearing
- Developmental delays and learning disabilities
- Autism spectrum disorder (ASD)
- Diseases of the heart, liver, or kidney
- Disorders of the gastrointestinal tract
- Difficulty swallowing, diarrhea, constipation, vomiting, cramping, and/or reflux
- Diabetes
- Frequent infections
- Neurological problems such as migraines, strokes, and seizures
- Movement disorders
- Problems with the thyroid
- Problems with breathing
- Buildup of lactate
- Dementia
Diagnosing Mitochondrial Diseases
Mitochondrial diseases are sometimes difficult to diagnose. This is because these diseases occur in many different organs and tissues, and the symptoms vary. No single test, laboratory or diagnostic, can confirm the presence of mitochondrial diseases. Instead, referral to a specialized facility that treats these diseases is vital in diagnosing them.
A doctor will perform various examinations and tests to diagnose a patient with a mitochondrial disease, including:
- Reviewing a patient’s family history
- A thorough physical examination
- A neurological examination
- A metabolic exam, including blood and urine tests
- A spinal tap
Other tests may be needed depending on the symptoms and affected areas. These tests could include:
- An MRI used to diagnose neurological disorders
- A retinal exam or electroretinogram used to diagnose vision problems
- An electrocardiogram or echocardiogram used to diagnose heart disease
- Audiogram responses used to diagnose hearing issues
- Blood tests to diagnose thyroid problems
- Blood tests to perform genetic DNA testing
- Biochemical testing to look for chemical changes
- Biopsies of the skin and muscle tissue
Mitochondrial Diseases Treatment
There are no cures for mitochondrial diseases, but research is ongoing, and there are treatments that can reduce symptoms and slow the progression of the disease.
The treatment a patient receives will depend on the disease, the organs affected, and the severity of the illness. Even if the same disease is present in two individuals, they may not respond to treatment in the same way.
Some treatments for mitochondrial disease include:
- Vitamins and supplements
- Various exercises to increase muscle size and strength
- Energy conservation
- Speech therapy
- Physical therapy
- Occupational therapy
Individuals with mitochondrial diseases are also advised to avoid situations that could cause their medical condition to worsen, such as exposure to excessive cold or heat, starvation, insufficient sleep, stress, and the use of cigarettes and alcohol. You may also want to avoid monosodium glutamate (MSG), which can commonly be found in Chinese food, canned vegetables, soups, and processed meats.
Mitochondrial Diseases Prognosis
Since mitochondrial diseases can affect different areas of the body and can range in severity, the outlook for each individual affected by mitochondrial diseases can vary. Some children and adults live normal lives with normal life expectancies. Others may experience an extreme decline in health within a short period of time. Flareups may affect some patients—these flareups can go into remission, though, and stabilize for years after.
If you or your significant other have a mitochondrial disease, you may want to consider consulting a genetic counselor before having children. That way, you can discuss your concerns and weigh your risks.