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Thursday, April 24, 2014
Inherited Disorders and Birth Defects
Could you tell me anything about Frederich's Ataxia. Am working with a 17 year old woman who has this diagnosis and have never heard of this condition.
Friedreich ataxia is a rare inherited disorder that affects the nervous system. It is seen in about 1 to 2 per 100,000 people. It is named after a German neurologist, Nikolaus Friedreich, who first described it in the mid 1800's.
Friedreich ataxia is an abnormality of the motor and sensory nerve conduction system and involves the spinal cord mainly, with degeneration of the spinal cord tracts. The major symptoms include progressive ataxia (incoordination of limb movements which becomes worse over time), dysarthria (problems with speaking), nystagmus (jerky movements of the eye muscles), a decrease in reflexes ( particularly there is a decrease in knee and ankle jerks), heart muscle disease and scoliosis (curvature of the spine). These findings begin in middle childhood, often with trouble walking. Most patients are wheelchair bound by their mid 40's. Some patients have lived into their 70's if there are no complications from heart disease or diabetes. There is no proven therapy that changes the neurological problems.
Friedreich ataxia is inherited as an autosomal recessive disorder. It is due to an abnormality in a gene called, frataxin mitochondrial protein, which is located on chromosome 9. It is inherited in the same way that cystic fibrosis or sickle cell anemia is inherited. A person with Friedreich ataxia has TWO abnormal genes and cannot produce the normal protein. One abnormal gene is inherited from their father; the other abnormal gene is inherited from their mother. The parents of a person with the disease are carriers for the gene, but do NOT have the disease themselves because the have one normal gene that overshadows the affect of the abnormal gene. Any couple that has had a child with Friedreich ataxia would have a 25% risk or 1 out of 4 chances of having another affected child with any future pregnancy.
Families who have someone with Friedreich ataxia in their family may benefit from talking to a geneticist or genetic counselor in their area about the inheritance of the disease and genetic testing.
Rimoin DL, Connor JM, Pyeritz RE (1997). Emery and Rimoin's Principles and Practice of Medical Genetics. 3rd ed. New York: Churchill Livingstone.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University