Symptoms include poor growth, loss of muscle coordination, muscle weakness, visual problems, hearing problems, learning disabilities, heart disease, liver disease, kidney disease, gastrointestinal disorders, respiratory disorders, neurological problems, autonomic dysfunction and dementia.
Acquired conditions in which mitochondrial dysfunction has been involved are diabetes, Huntington’s disease, cancer, Alzheimer’s disease, Parkinson’s disease, bipolar disorder, schizophrenia, aging and senescence, anxiety disorders, cardiovascular disease, sarcopenia and chronic fatigue syndrome.
- Increased risk of infection
- Thyroid and/or adrenal dysfunction
- Neuropsychological changes characterised by confusion, disorientation, and memory loss.
- Autism, autistic spectrum, autistic-like features
- Visual and/or hearing problems possibly even blindness and deafness
- Developmental delays, learning disabilities
The body, and each mutation, is modulated by other genome variants; the mutation that in one individual may cause liver disease might in another person cause a brain disorder. The severity of the specific defect may also be great or small. Some minor defects cause only “exercise intolerance”, with no serious illness or disability. Defects often affect the operation of the mitochondria and multiple tissues more severely, leading to multi-system diseases.
As a rule, mitochondrial diseases are worse when the defective mitochondria are present in the muscles, cerebrum, or nerves, because these cells use more energy than most other cells in the body.
Although mitochondrial diseases vary greatly in presentation from person to person, several major clinical categories of these conditions have been defined, based on the most common phenotypic features, symptoms, and signs associated with the particular mutations that tend to cause them.