SYSTEMATIC SCREENING FOR FRAGILE-X-SYNDROME IN A COHORT OF 574 MENTALLY-RETARDED CHILDREN

In this study, we evaluated the prevalence of the fragile X syndrome i n a cohort of 574 mentally retarded children. The only inclusion crite rion was the diagnosis of mental retardation according to the DSM-IIIR classification, We used a PCR-based strategy for the diagnosis of fra gile X syndrome to facilitate systematic screening, This diagnostic sc heme is based on an initial PCR to eliminate most fragile X-negative p atients followed by Southern blotting for fragile X syndrome diagnosis , Altogether, 403 boys and 171 girls were tested. The prevalence of th is genetic disorder was 1.9 % (11/574) in the whole cohort and 2.5 % ( 10/403) in boys, Only one case of fragile X syndrome was detected amon g the 171 girls tested (0.6%). Clinical examination, especially in the youngest children, was often unremarkable, and the only reason for su specting fragile X syndrome was the presence of mental retardation, Th us, a systematic screening for the fragile X syndrome in mentally reta rded children seems justified because of the importance of a precise d iagnosis in genetic counseling.