Friedreich's ataxia is an inherited (genetic) disorder that causes certain nerve cells to deteriorate over time. In many cases, this disorder also affects the heart, certain bones and cells in the pancreas that produce insulin. The illness typically begins with difficulty walking. People with Friedreich's ataxia develop clumsy, shaky movements of the legs (called gait ataxia) during childhood or early adolescence. In rare cases, symptoms appear in infants and in middle-aged adults. As the disease gets worse, people may develop bony deformities of the spine and feet, loss of sensation in the limbs, speech problems, abnormal eye movements, heart disease and diabetes.
Scientists believe that many symptoms of Friedreich's ataxia are related to abnormally low levels of frataxin, a protein that helps to protect cells from "free radicals," which are toxic (poisonous) byproducts of the cells' energy production. In a person with Friedreich's ataxia, a segment of the genetic code on chromosome number 9 can have as many as 1,000 repetitions, instead of the normal range of 7 to 22. These repetitions produce an error that leads to a decreased production of frataxin. As free radicals accumulate within cells, and more and more cells are destroyed or altered, the long-term effects of Friedreich's ataxia lead to a thinner spinal cord, enlarged heart muscle, disturbances in speech and eye movement, and loss of the pancreas's ability to regulate blood sugar. Ultimately, almost everyone with Friedreich's ataxia is confined to a wheelchair, and a large percentage of people develop serious heart problems, including heart failure.
Friedreich's ataxia is a recessive disorder, which means that 2 copies of the abnormal ninth chromosome must be inherited (1 from each parent). People who inherit only one abnormal copy (approximately 1 of every 90 Americans of European ancestry) don't have the disease, but are "carriers" who can pass the abnormal chromosome to their children.
In the United States, there is a 1 in 50,000 chance that a child will inherit two copies of the abnormal ninth chromosome that produces Friedreich's ataxia. In 85% of cases, symptoms develop before age 25, but rarely before age 5. Although people from all parts of the world suffer from Friedreich's ataxia, studies show that their ancestry is almost always European, North African, Middle Eastern or Indian (Indo-European).