Friedreich’s ataxia is a hereditary disorder that leads to progressive and irreversible damage to the nervous system. The condition can eventually cause cardiac problems and diabetes.
Friedreich’s ataxia was first described by a German physician Nicholaus Friedreich in 1863, after whom the disease is named.
Initial symptoms usually include disturbances in balance, limb coordination and speech, problems that gradually worsen as the disease progresses.
Other symptoms that develop include high foot arches and curvature of the spine, which can cause an impaired sense of body position (proprioception) and eventually lead to weakness in the limbs.
Cardiac complications such as enlarged heart, arrhythmia and cardiomyopathy are other common symptoms and range in severity from mild to serious. There is also an increased risk of developing diabetes.
As the disease advances to a later stage, around 10% of sufferers start to develop hearing loss and a similar proportion develop visual disturbances. Incontinence is another common complication of the condition that eventually affects around half of sufferers.
Friedreich’s ataxia is a genetic disorder caused by a mutation in the frataxin (FXN) gene. The condition is inherited in an autosomal recessive manner, meaning both copies of the gene need to be abnormal if a person is to develop symptoms of the disease.
A person with only one abnormal copy of the gene does not develop the condition but is termed a carrier. In a carrier, the abnormal FXN gene is effectively “cancelled out” by the presence of a normal FXN gene.
However, if that carrier’s offspring inherit their one abnormal copy of the gene, along with a second abnormal copy from their other parent, then they will develop Friedreich’s ataxia.
Mutation of the FXN gene leads to low levels of frataxin, a protein that binds iron. One outcome of frataxin deficiency is mitochondrial iron overload, which leads to oxidative damage in cells.