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Diagnosis Return to Index

Diagnosing FA
Who/Why/Where/How/What

Where did FA come from?
What is FA?
Who has FA?
Where does one do the DNA test(s) for FA?
Asymptomatic Testing


Your son or daughter has symptoms of ataxia (incoordination) or scoliosis or hypertrophic cardiomyopathy and your doctors have been trying to "name the blame", what is it they have? Could it be FA?

The search that leads to FA is not an easy one. Look at this shortened 2007 presentation from the wonderful UCLA Dr. Susan Perlman, 2007 Dr. Perlman Diagnosis Only Presentation that covers many of the alternative diagnoses and FA DNA diagnosing. Also in the FARA "Clinical Care Guidelines", http://www.curefa.org/clinical-care-guidelines, section 1.5 "Differential Diagnosis" there is an excellent coverage of alternate diagnoses.

Where did FA come from?
The FA gene is European in origin and its first incidence goes back many millennia, so one would expect the greatest FA density to be in European settled areas (USA, Canada, Australia for instance) with the least density in areas such as Africa, South America, and China for instance. Take a look at the FAPG map to prove this out, http://www.faparents.org/fapg/OurFamilies/Map/.

What IS FA?
FARA has a good set of web pages at http://www.curefa.org/whatis For a layman's rendition of what is FA see "What is FA Rev 4".

The FA gene can err in one of several ways. It can have an abnormally long GAA sequence or it can have a mutation in the gene called a point mutation or axon deletion. About 96% of FA'ers have two abnormally long GAA repeats from around 60 repeats to 1700 repeats. The other 4%-ish have one or more point mutations (or axon deletions which are exceedingly rare and not covered here). So when one wants a DNA test for FA the first and least expensive test is for 2 expanded GAA repeat genes. If that comes back negative or just one expanded GAA repeat gene then do the more expensive test for point mutations. The third test for axon deletions is then even more expensive.

Who has FA?
Before 1996 FA was diagnosed by symptoms. This started in 1863 when Dr. Friedreich isolated the symptoms of FA. In 1996 the location of the gene that causes FA was identified (9q21.11) and a DNA test shortly thereafter was put in place.

The FA carrier incidence rate varies from country to country and by sub-population. If you are in the "Cajun" area of Louisiana the rate is 1/40 people, but if you live say in the middle of China the rate would be very, very low, say 1/10,000 to 1/100,000 (purely a guess on the author's part - a negligible chance). The average in European family trees is about 1/100.

The chance for two "average" FA carriers is about 1/100 times 1/100 or 1/10,000. If they have a baby the baby's chance for FA is 1/4.

So the chance for a FA birth in an average European-descended family is somewhere around 1/40,000 (FARA uses 1/50,000).

Where does one do the DNA test(s) for FA?
Once one suspects FA it is DNA test time! But where? Your doctor may know and your medical insurance may pay for the testing. That would be good. In case YOU have to pay for it or your doctor doesn't know or you want an anonymous test here is a sample list of DNA test centers.


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