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A mitochondrion (singular of mitochondria) is part of every cell in the body that contains genetic material, other than nucleus. Mitochondria are responsible for processing oxygen and converting substances from the foods we eat into energy in the form of adenosine triphosphate (ATP) for essential cell functions.

Mitochondrial disorders

The process of converting food and oxygen (fuel) into energy requires hundreds of chemical reactions, and each chemical reaction must run almost perfectly in order to have a continuous supply of energy. When one or more components of these chemical reactions do not run perfectly, there is an energy crisis, and the cells cannot function normally. As a result, the incompletely burned food might accumulate as poison inside the body.

This poison can stop other chemical reactions that are important for the cells to survive, making the energy crisis even worse. In addition, these poisons can act as free radicals (reactive substances that readily form harmful compounds with other molecules) that can damage the mitochondria over time, causing the mitochondrial disorders. There are about 40 mitochondrial disorders, which affect multiple organs of our body.

Symptoms of mitochondrial disorders

The types of mitochondrial diseases are categorized according to the organ systems affected and symptoms present. Mitochondrial diseases might affect the cells of the brain, nerves (including the nerves to the stomach and intestines), muscles, kidneys, heart, liver, eyes, ears, or pancreas. In some patients, only one organ is affected, while in other patients all the organs are involved. Depending on how severe the mitochondrial disorder is, the illness can range in severity from mild to fatal.

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)

Prevalence of mitochondrial disorders

Current estimates place the incidence of mitochondrial disorder at about 1 in 2000 to 1 in 5000 live births. 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.

Diagnosis of mitochondrial disorders

Diagnosis of mitochondrial disease can be invasive, expensive, time-consuming, and labor-intensive. Therefore, evaluation is not taken lightly. Doctors experienced in diagnosing and treating these diseases will take either a step-wise approach to diagnosis or, in some centers, the evaluation takes place over a few days. The evaluation includes a combination of clinical observations and laboratory tests.

Under ideal circumstances, the evaluation will produce an answer. However, even after a multiple evaluations, the doctor might not be able to confirm a specific diagnosis or put a name to the disorder. In many cases, however, the physician will be able to identify which patient does and doesn't have mitochondrial disease.

Mitochondrial disease is diagnosed by

  • Evaluating the patient's family history
  • Performing a complete physical examination
  • Performing a neurological examination
  • Performing a metabolic examination that includes blood, urine, and optional cerebral spinal fluid tests
  • Performing other tests, depending on the patient's specific condition and needs. These tests might include:
  • Magnetic resonance imaging (MRI) or scan (MRS) if neurological symptoms are present
  • Retinal exam or electroretinogram if vision symptoms are present
  • Electrocardiogram (EKG) or echocardiogram if heart disease symptoms are present
  • Audiogram or BAEP if hearing symptoms are present
  • Blood test to detect thyroid dysfunction if thyroid problems are present.
  • Blood test to perform genetic DNA testing

More invasive tests, such as a skin or muscle biopsy, might be performed as needed and recommended by your doctor.

  • Defined mitochondrial disorders
  • Some of the defined mitochondrial diseases and the disorders where mitochondrial defect is confirmed include
  • Chronic Progressive External Ophthalmoplegia (CPEO)
  • Diabetes Mellitus
  • Kearns Sayre Syndrome
  • Leber Hereditary Optic Neuropathy (LHON)
  • Mitochondrial Cardiomypathy
  • Mitochondrial myopathy
  • Mitochondrial Encephalomyopathy
  • Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS)
  • Myoclonic Epilepsy and Ragged Red Muscle Fibers (MERRF)
  • Maternally Inherited Leigh Syndrome (MILS)
  • Neuropathy, Ataxia, and Retinitis Pigmentosa(NARP)
  • Sensorineural Hearing Loss
  • Alzheimer's Disease

Treatment of mitochondrial disorders

There are no cures for mitochondrial diseases, but treatment can help reduce symptoms, or delay or prevent the progression of the disease. Treatment is individualized for each patient, as doctors specializing in metabolic diseases have found that every child and adult is "biochemically different." That means that no two people will respond to a particular treatment in a specific way, even if they have the same disease.

Certain vitamin and enzyme therapies, along with occupational and physical therapy, might be helpful for some patients. Vitamins and supplements prescribed might include: