Friedreich ataxia (FA) is caused by a GAA expansion in the first intron of the frataxin gene (FXN) in 96% of the affected individuals. The remaining patients have a GAA expansion in one allele and a point mutation in the other. Little is known about compound heterozygous patients outside Europe and North America. This group has designed a study to determine the frequency and mutational profile of these patients in Brazil. They recruited all patients with ataxia and at least one expanded GAA allele at FXN from 3 national reference centers and identified those subjects with a single expansion and completed further genetic testing. There were 143 unrelated patients (128 families), five of which had a single expanded allele. They identified point mutations in three out of these five (3/128 = 2.34%). Two patients had the c.157delC variant, whereas one individual had the novel variant c.482+1G>T. These results indicate that FXN point mutations are rare, but exist in Brazilian patients with FRDA. This has obvious implications for diagnostic testing and genetic counseling.
Read the entire article HERE