Development and Symptoms

There is no one identifying feature of mitochondrial disease. Patients can have combinations of problems whose onset may occur from before birth to late adult life. Typically, the earlier the onset of symptoms, the more severe the disease. Symptoms can be progressive and may include, but are not limited to, combinations of the following: seizures, developmental delay, regression, movement disorders, migraines, strokes, cardiac problems, hearing deficit, eye muscle dysfunction and visual loss, diabetes, GI problems, temperature irregularities, fatigue, failure to gain weight, mental retardation, autism, behavior problems, and dementia. Siblings with the same defect can have differing levels and types of symptoms.

Three "rules of thumb" generally characterize mitochondrial disorders:

•  A "common disease" (such as diabetes) has atypical features

•  Three or more organ systems are involved

•  Recurrent setbacks or flare-ups of the disease occur with acute infections