Friedreich's ataxia is an autosomal recessive inherited disease that causes progressive damage to the nervous system. It manifests in initial symptoms of poor coordination such as gait disturbance; it can also lead to scoliosis, heart disease and diabetes, but does not affect cognitive function. The disease progresses until a wheelchair is required for mobility. Its incidence in the general population is roughly 1 in 50,000.
The particular genetic mutation (expansion of an intronic GAA triplet repeat in the FXN gene) leads to reduced expression of the mitochondrial protein frataxin. Over time this deficiency causes the aforementioned damage, as well as frequent fatigue due to effects on cellular metabolism.
The ataxia of Friedreich's ataxia results from the degeneration of nervous tissue in the spinal cord, in particular sensory neurons essential (through connections with the cerebellum) for directing muscle movement of the arms and legs. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath (the insulating covering on some nerve cells that helps conduct nerve impulses).
The condition is named after the German physician Nikolaus Friedreich, who first described it in the 1860s.[1]
Friedreich, working as a professor of pathology at the University of Heidelberg, reported five patients with the condition in a series of three papers in 1863.[2][3][4] Further observations appeared in a subsequent paper in 1876.[5]
Symptoms typically begin sometime between the ages of 5 to 15 years, but in Late Onset FA may occur in the 20s or 30s. Symptoms include any combination, but not necessarily all, of the following:
It presents before 25 years of age with progressive staggering or stumbling gait and frequent falling. Lower extremities are more severely involved. The symptoms are slow and progressive. Long-term observation shows that many patients reach a plateau in symptoms in the patient's early adulthood. On average, after 1015 years with the disease, patients are usually wheelchair bound and require assistance with all activities of daily living.[7]
The following physical signs may be detected on physical examination:
20% of cases are found in association with diabetes mellitus.[6]
Friedreich's ataxia is an autosomal recessive disorder that occurs when the FXN gene contains amplified intronic GAA repeats. The FXN gene encodes the protein frataxin.[8] GAA repeat expansion causes frataxin levels to be reduced. Frataxin is an iron-binding protein responsible for forming ironsulphur clusters. One result of frataxin deficiency is mitochondrial iron overload which can cause damage to many proteins.[8] The exact role of frataxin in normal physiology remains unclear.[9] The gene is located on chromosome 9.
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Friedreich's ataxia - Wikipedia, the free encyclopedia
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