Mitochondrial Disease - What it is and How it is Inherited

Mitochondrial disease is a disorder related to the mitochondria. The mitochondria are organelles which are also known as the power houses of the cells. They convert the energy of food molecules into the ATP (ATP or Adenosine triphosphate transports chemical energy within cells for metabolism that powers most cell functions). So basically the mitochondria provide energy to the cells which allows the cells to grow and do their work in our body. If the mitochondria are damaged or malfunctioning, then the cells do not work as they should. Since mitochondria are present in every cell of our body their failure can result in many problems. Mitochondrial disease may cause various disorders that vary from person to person. It may cause brain disorder for one person while for another person it may cause liver disorder.

Mitochondrial disease is inherited differently from other diseases. For all other cases and cells (except for sperm and egg), the nuclear DNA has two copies per cell, one is inherited from the father while the other is inherited from the mother. But Mitochondria contain their own DNA and typically have five to ten copies; all of which are inherited from the mother. Now when the mitochondrion divides, the copies of DNA present are divided randomly between the two new mitochondria, these two mitochondria further divide into more mitochondria and so on. So if only some of the original DNA copies inherited from the mother were defective, then after this division there is a high probability that most of the defective copies end up in just one of the new mitochondria. The symptoms of mitochondrial disease become apparent once the number of affected mitochondria reaches a certain threshold level. That is why mitochondrial disease is a rare disease.

The types of mitochondrial diseases are categorized according to the organ systems affected and symptoms present. In some patients, only one organ is affected, while in other patients all the organs are involved. Depending on which cells of the body are affected, symptoms might include:

• Poor growth.
• Loss of muscle coordination, muscle weakness.
• Visual and/or hearing problems.
• Developmental delays, learning disabilities.
• Mental retardation.
• Heart, liver, or kidney disease.
• Gastrointestinal disorders, severe constipation.
• Respiratory disorders.
• Diabetes.
• Increased risk of infection.
• Neurological problems, seizures.
• Thyroid dysfunction.
• Dementia (mental disorder characterized by confusion, disorientation, and memory loss). 

Mitochondrial disease is a rare disease and appears in about one in every 4,000 children in the United States alone. One thousand to 4,000 children per year in the United Sates are born with a type of mitochondrial disease. 

Sadly, there is no cure for mitochondrial diseases. But treatment can help reduce symptoms, or delay or prevent the progression of the disease. Treatment is individualized for each patient since every child and adult is "biochemically different". Hence the same treatment cannot be applied on two different persons even if they have the same disease.

Some helpful treatments include vitamins such as thiamine (B1), riboflavin (B12), vitamin C, and vitamin E. Lipoic acid and coenzyme Q-10 are also useful supplements. Also Pyruvate or Pyruvic acid which plays an important role in biochemical processes, is being considered as a treatment option by researchers.