Direct mutation analysis of 495 patients for fragile X carrier status/proband diagnosis.

With the cloning of the FMR-1 gene, direct mutation analysis is possible for fragile X syndrome. We have analyzed 495 patients using the StB12.3 probe/EcoRI/EagI system of Rousseau et al. [N Engl J Med 325:1673-1681, 1991] and 167 of these also with PCR analysis according to Brown et al. [JAMA 270:1569-1575, 1993]. For 28 patients requesting carrier status due to a family history of fragile X, 10 were shown to have either premutations or full mutations; for the remainder with varied backgrounds, 1 in 182 was shown to carry a premutation. For proband diagnosis, 7 of 14 with a fragile X family history carried a full mutation; 11 of 271 with other family histories carried the full mutation.