THE PREVALENCE OF THE FMR1 AND FMR2 MUTATIONS AMONG PRESCHOOL-CHILDREN WITH LANGUAGE DELAY

We examined the prevalence of the fragile X mental retardation (FMR1) full mutation and fragile X E mutation (FMR2) among preschoolers evalu ated for language delay. A total of 534 preschoolers recruited from a Developmental Pediatric or Speech and Language Disorders clinic were t ested with Southern blot and polymerase chain reaction DNA analyses; 3 were found to have the FMR1 full mutation. None of the 534 children t ested positive for the FMR2 full mutation; however, 3 children had unu sually small FMR2 alleles suggestive of FMR2 deletions. Screening for fragile X among language-delayed preschoolers is warranted, particular ly when there is a family history of mental retardation, but regardles s of sex or the presence of behavioral or physical features associated with the fragile X phenotype. The potential benefit of screening for FMR2 alterations is an unexpected implication of the study and is wort hy of continued exploration.