Prenatal diagnosis of Friedreich ataxia.

Friedreich ataxia is a progressive neurodegenerative disorder affecting the peripheral and central nervous systems. One in 50,000 of the population are affected by this recessively inherited disorder, with onset usually before puberty. The recent localization of the disease locus to chromosome 9 has made it possible to provide genetic counselling to families with at least one affected child. Tight linkage of the disease mutation to an anonymous DNA marker MCT112 (D9S15) has been shown with a pairwise lod score of 36.1 at 0 = 0. We report here the first prenatal diagnosis in Friedreich ataxia. Using MCT112 and the confidence interval approach, we have calculated risks for a fully informative family with one affected sib.