Mitochondrial Q & A
- What are mitochondria?
- What is a mitochondrial disease?
- What are some symptoms of a mitochondrial disease?
- How common are mitochondrial diseases?
- When do doctors suspect that a person may have a mitochondrial disorder?
- Is there a cure for mitochondrial diseases?
- How is a mitochondrial disease inherited?
- What is Alpers?
Mitochondria (plural for mitochondrion) are sometimes described as cellular “power plants” because among other things, mitochondria are responsible for creating more than 90% of the energy needed by the body to sustain life and support growth. In addition to making energy, mitochondria are also deeply involved in a variety of other activities, such as making steroid hormones and manufacturing the building blocks of DNA.
Mitochondrial diseases result when your body’s mitochondria fail to function properly. Your body’s organ systems are severely affected when your mitochondria can’t provide the energy needed to keep them running. Some parts of the body that require the most energy to function are: the brain, heart, liver, skeletal muscles, kidneys, endocrine and respiratory systems.
Given the fact that mitochondria are responsible for fueling nearly all of the body’s energy needs, there is a long list of symptoms depending on which organ or tissue is having the “energy crisis.” When symptoms arise from three or more organ systems a mitochondrial disease should definitely be considered.
- poor growth (failure to thrive)
- muscle weakness, poor coordination
- sensory (vision, hearing) problems
- reduced mental functions
- disease of the organ (heart, liver)
- respiratory problems
- lactic acidosis
- gastro-intestinal disorders and swallowing difficulties
- developmental delays
- movement disorders (dystonia, muscle spasms, tremors, chorea)
- brain atrophy
It is now said that mitochondrial diseases are nearly as common as childhood cancer! One in 4,000 children born in the United States every year will develop a mitochondrial disorder by age 10. In adults, many diseases of aging have been found to have defects of mitochondrial function. These include, but are not limited to, type 2 diabetes, Parkinson’s disease, atherosclerotic heart disease, stroke, Alzheimer’s disease, and cancer. In addition, many medicines can injure the mitochondria.
Different symptoms indicative of mitochondrial diseases may present over time. As patients begin to present with multiple catastrophic symptoms it can be hard for physicians to pinpoint the main cause. It is crucial that they never remove or set aside a symptom to try and diagnose the problem. All symptoms must be given consideration.
Mitochondrial disease should be suspected when:
- A “common disease” has atypical features that set it apart from the pack
- Three or more organ systems are involved
- Recurrent setbacks or flare ups in a chronic disease occur with infections
There is not a cure for mitochondrial diseases. Doctors must look at each patient on a case-by-case basis and try to develop a treatment plan. Treatment may involve special diets and/or a combination of vitamins, and reducing any stress on the body.
The types of mitochondrial disease inheritance include:
- Nuclear DNA (DNA contained in the nucleus of the cell) inheritance. Also called autosomal inheritance.
— If this gene trait is recessive (one gene from each parent), often no other family members appear to be affected. There is a 25 percent chance of the trait occurring in other siblings.
— If this gene trait is dominant (a gene from either parent), the disease often occurs in other family members. There is a 50 percent chance of the trait occurring in other siblings.
- MtDNA (DNA contained in the mitochondria) inheritance.
— There is a 100 percent chance of the trait occurring in other siblings, since all mitochondria are inherited from the mother, although symptoms might be either more or less severe.
- Combination of mtDNA and nDNA defects:
— Relationship between nDNA and mtDNA and their correlation in mitochondrial formation is unknown
- Random occurrences
— Diseases specifically from deletions of large parts of the mitochondrial DNA molecule are usually sporadic without affecting other family members disease
Alpers’ Syndrome is a disease of the brain and liver. There are 3 classical symptoms of Alpers’ Syndrome. These are: 1) seizures that are very difficult to treat and have a focal component, 2) episodic psychomotor regression or dementia (loss of developmental milestones, often associated with common childhood infections),
3) liver disease. The children are born and develop normally for a period of time in virtually every case. Symptoms begin between the first few weeks of life and about 25 years of age. Two-thirds of the cases begin to show symptoms of seizures, or episodic loss of developmental milestones, within the first 2 years of life. The liver disease is often subclinical in the early stages of disease, but can appear at any time as acute liver failure.
Alpers’ Syndrome is a recessive genetic disease with a frequency of about 1:250,000 live births. Many cases die before an accurate diagnosis is made, so the true frequency is still an estimate. Alpers is caused by inheriting two copies of the POLG gene that are dysfunctional. These are called mutant copies. The function of the POLG gene is to copy mitochondrial DNA. In Alpers’ Syndrome, POLG is defective, so after a period of time, the amount of mitochondrial DNA in the cell falls below a critical threshold of about 35% of normal. When this happens, the mitochondria become sick, and begin to misfire. This leads to the brain and liver disease of classical Alpers’ Syndrome.
Information provided is intended for educational purposes only and should not be construed as advising or diagnosing or treatment of this or any other medical condition.