What is Mitochondrial Disease?
Mitochondrial diseases are not one disease, but a group of metabolic diseases. These diseases result from failures of the mitochondria, specialized organelles present in almost every cell of the body. Mitochondria are responsible for providing more than 90% of the energy needed by the body to sustain life and support growth. Food is converted into ATP (stored energy) by means of enzymes in the electron transport chain (or respiratory chain) inside the mitochondria. The process itself is called oxidative phosphorylation. Defects in either the mitochondrial DNA or the DNA of the nucleus can impair this process and cause mitochondrial failure.
When mitochondria fail, less and less energy is generated within the cell. When this happens, cell injury and even cell death follow. If this process is repeated on a large scale throughout the body, whole systems begin to fail. The life of the affected person is compromised, changed or even ended.
Hallmark of Mitochondrial Disease
1. A “common disease” has atypical features that set it apart from the pack.
2. More than one organ systems are involved.
3. Recurrent setbacks or flare-ups in a chronic disease occur with infection.
How many individuals are affected?
Every 15 minutes a child is born who will develop mitochondrial disease by the age of 10. We now know that this group of diseases is approaching the frequency of childhood cancers. The exact numbers of children and adults with mitochondrial disease are hard to determine because of people who suffer from a mitochondrial disease are misdiagnosed. Some are misdiagnosed with such conditions as: atypical cerebral palsy, various seizure disorders, other childhood diseases and diseases of aging, chronic fatigue or fibromyalgia.
What are the causes?
Mitochondrial diseases can be due to inherited mutations or acquired mutations. There are primary (something inherently wrong with mitochondrial function) and secondary (the mitochondria are injured as a bystander to another process) disorders.
Mitochondrial disorders can be inherited in different ways. In fact, nearly every inheritance “model” known has been demonstrated to occur in mitochondrial disease. However, most mitochondrial disorders known to date are inherited in either an autosomal recessive (both parents are unaffected carriers) or maternal manner.
In many cases, the patient is the only family member affected with a mitochondrial disease. These cases are called “sporadic” and make answering the questions regarding inheritance more difficult.
Signs and symptoms
Patients’ symptoms can range from extremely mild to severe, involve one or more body systems, and can emerge at any age. Most patients’ symptoms fluctuate over the course of their illness – at some time experience no or few symptoms while at other times experiencing many and/or severe symptoms. Symptoms may present unexpectedly at any age, or they may be evident from birth or infancy. Diseases of the mitochondria appear to cause the most damage to cells of organs and systems that require a great deal of energy: the brain, the heart, the skeletal muscles, the GI system, the kidneys, the liver, and the endocrine and respiratory systems. Many face numerous, severe problems and the potential for premature death. Mitochondrial diseases are extremely complex; due to this complexity, the severity of these diseases is unpredictable, and the range of symptoms is diverse.
Even though mitochondrial disorders are long term and currently incurable, treatments are available. Early treatment of symptoms can reduce their impact and limit further disability. Avoiding various medications and stressful situations that worsen symptoms is also helpful. Certain medications and supplements may improve mitochondrial disease related symptoms – just as they do for other incurable diseases such as diabetes and emphysema.
Therapeutic interventions, e.g. speech therapy, physical therapy, occupational therapy, and respiratory therapy, may be necessary for some mitochondrial disease patients. While they will not change the primary condition, they may be necessary to preserve and possibly improve current function, strength and mobility.
Things to Avoid
Stress can cause energy depletion, which may result in temporary, or sometimes permanent, worsening of the condition. Is it impossible to avoid all physiologically stressful conditions. However, recognizing what may be stressful for a patient allows one to adjust the lifestyle.
Cold stress avoidance is extremely important. Thermal regulation is not always normal in people with mitochondrial diseases and exposure to cold can result in severe heat loss and trigger an energy crisis. When going out into the cold, all exposed body parts should be covered, and exposure to extreme cold should be avoided for anything more than a short period. Over-bundling can be a problem too.
Heat stress can be a problem in some people. This is especially true of those with an inability to sweat normally. Heat exhaustion and heat stroke may occur on hot days. Light clothing is important. Patients should avoid direct sunlight on hot days and stay indoors if too warm outside. An air condition environment may be needed.
Lack of sleep may be harmful. Rest is extremely important to mitochondrial patients.
Illness – especially with fever should be treated as soon as possible.
Stressors - specific to the individual patient.
It is not possible to chart the future of a person with a mitochondrial disorder. Those with a higher number of defective mitochondria do worse, on average, than those with a lesser number, but this is only valid for populations of patients and cannot be used to predict what will occur in any one patient.