Mitochondrial disease is a hereditary condition that occurs due to damage of mitochondria and its subsequent dysfunction. It is marked by problems of the muscle, cardiac, and brain systems; the accompanying symptoms may vary in severity levels. The disease may be congenital or occur later in life.
The mitochondria are elongated structures that occur in all cells of the body other than RBCs. They are enclosed by the outer and inner membranes of the cells. Known as ‘the powerhouse of cells,’ mitochondria help in making energy and also contain many enzymes and proteins needed by the body for breaking down carbohydrates and fats, etc. Hence, damage and malfunction of mitochondria can result in widespread abnormalities of varied body systems.
The ailments caused due to mitochondrial disease are many and occur in several forms; a few neuromuscular conditions in adults include Kearns-Sayre syndrome and mitochondrial encephalomyopathy with stroke-like bouts and lactic acidosis, while children may suffer from Pearson syndrome or MDS/mitochondrial DNA depletion syndrome. The incidence rate of mitochondrial disease in the US is 1 in every 3000 to 4000 people; 1 in every 4000 children may develop the condition by the time they turn 10 years old.
Mitochondrial disease has no known cure. Treatment is aimed at managing the symptoms with medications and diet therapies to boost energy as well as preventing the onset of health complications.
Symptoms of Mitochondrial Disease
The occurrence of the many signs and symptoms of mitochondrial disease is dependent on the body system that gets affected. Listed below are some common symptoms classified according to the affected body systems.
- The central nervous system: Affected individuals may experience delays in development, dementia, learning disabilities, seizures, mental retardation, and other neurological issues. Developmental delays tend to be more visible in children with brain defects as it can hamper central nervous system operations.
- The musculoskeletal system: Affected people may experience lack of growth; easy fatigue and lethargy; low muscle tone; stunted growth; low or absent muscle coordination; and muscle cramping, weakness, and pain. Deficient endurance capabilities, speaking and swallowing difficulties, and imbalance may also be evident.
- The cardiovascular system: Mitochondrial disease severely affects the energy levels. The cardiac muscle is dependent on energy for efficient function. Hence, patients experience problems of the heart muscles. Arrhythmia, cardiac diseases, and heart failure may also occur.
- The respiratory system: Mitochondrial disease may also directly affect the energy-dependent pulmonary muscles which can then affect the breathing process and cause varied respiratory problems such as shortness of breath, etc.
- Eye and ear problems: Patients may suffer from restricted eye movements, eye twitching, cataracts, ptosis or droopy eyelids, loss of vision/blindness, and other ocular conditions. Deafness and hearing problems may also occur.
- Other body system defects: Patients may also experience kidney and liver diseases, gastrointestinal problems, increased infections, diabetes, extreme constipation, thyroid malfunction, vomiting, intolerance to exercising, and nausea.
- Associated conditions: Symptoms of associated disorders are:
- Mitochondrial encephalomyopathy with stroke-like bouts and lactic acidosis may be marked by diabetes, hearing loss, migraines, and strokes.
- MDS may be marked by feeding problems, muscle weakness, brain irregularities, liver dysfunction, and delays in achieving developmental milestones like crawling walking, etc. Muscle fatigue is common in adults, while affected children may elicit full-blown symptoms before age 20 years.
- Pearson syndrome may be marked by anemia and pancreas dysfunction. Affected children may suffer from lethargy, episodes of total fatigue, and concentration problems which may result in oscillating productivity at school.
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Causes
Mitochondrial disease is caused due to mutations, changes, or errors in the nDNA or mtDNA genes, which in turn affect the functioning of RNA molecules or proteins occurring in mitochondria, leading to mitochondrial dysfunction.
Mitochondria occurs in all cells of the body with the exception of red blood cells. They play a vital role in the production of energy which is critical to growth and sustenance of life. Their dysfunction or failure can result in progressively lowered production of energy within each cell, cell damage, and even death of the cells. Repetition of this process across the body can eventually result in failure of varied body systems, especially the heart, skeletal muscles, brain, kidneys, liver, and the respiratory and endocrine systems. Thus, mitochondrial disease can prove to be life-threatening.
It is possible for mitochondrial disease to affect only certain tissues. This may occur due to unknown factors at the time of growth and development. Also, the causes of variance in the severity levels of the associated tissue defects are not known.
It is possible for the genetic mutations to be passed down from the parents, or it may occur spontaneously. The causes are not known, though children with a family history of the condition are at greater risk to developing mitochondrial disease. It is more common in children, but incidences of adult-onset mitochondrial disease is currently on the rise.
There are 4 known types of mitochondrial disease, namely, Leigh’s disease, Lhon, creatine deficiency syndrome, and (PDCD/PDH) pyruvate dehydrogenase complex deficiency.
Treatment
Currently, there is no way to cure genetic defects and hence mitochondrial disease has no known cure. Early treatment is more effective and helps stop the migration of the condition to other body systems. Treatment options are usually dependent on the body systems that are affected and the severity of the associated symptoms.
- Doctors may opt for physical therapy and varied medications.
- Intake of vitamins like E, C, K, lipoic acids, riboflavin, carnitine, idebenone, and coenzyme Q in addition to antioxidants can boost energy, stop the transmission of free radicals, and decrease fatigue.
- Lifestyle changes like quitting smoking and alcohol intake.
- Dietary changes such as intake of a healthy and balanced diet full of fresh fruits, vegetables, and whole grains; drinking lots of water to keep the cells hydrated; and avoiding sugar rich foods.
Mitochondrial disease life expectancy
The life expectancy of mitochondrial disease patients is dependent on varied factors, including early diagnosis, number of body systems that are affected, severity levels of associated symptoms, and whether or not it is an adult-onset or congenital form of the disease.
The average life expectancy of adult patients is about 49 years. The low life expectancy can be attributed to the progressive weakening of the affected body systems. In some cases, children with mitochondrial disease may die in the first year of life.
