Mitochondrial diseases are a group of progressive metabolic, often neurological, disorders that result from defects in the mitochondria, which are in almost every type of cell in the body. Mitochondria are responsible for creating more than 90% of the energy needed to sustain life and support growth. Mitochondrial failure results in energy deprivation within the cells. Cell injury and even cell death follow. If this process is repeated throughout the body, whole systems begin to fail, and the affected person's life is severely compromised. The disease primarily affects children, but adult onset is becoming increasingly common.
Diseases of the mitochondria appear to cause the most damage to organs requiring high energy levels including: brain, heart, liver, skeletal muscles, kidney, eyes, and the endocrine and respiratory systems.
Mitochondrial disorders are notorious for not following a set pattern. It is not uncommon for patients to first be misdiagnosed with another disorder. Symptoms can begin at any age. Depending on which cells are affected, symptoms may include: loss of motor control, muscle weakness and pain, gastro-intestinal disorders and swallowing difficulties, poor growth, cardiac disease, liver disease, diabetes, respiratory complications, seizures, visual/hearing problems, lactic acidosis, developmental delays, autism, and susceptibility to infection.
Mitochondrial disorders are not always physiologically obvious. Intelligence can range from gifted to profoundly retarded. Children with fewer affected mitochondria may be mislabeled as lazy, uncooperative, or underachievers. At the beginning of the school day, for example, they may appear energetic and focused. But as the day progresses, their small reserve of energy evaporates and they are unable to complete the same tasks as their classmates. These children may also be labeled as mildly retarded because of their slowness, when in reality they may be merely fatigued.