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 evaluated for language delay. A total of 534 preschoolers recruited from a Developmental Pediatric or Speech and Language Disorders clinic were tested with Southern blot and polymerase chain reaction DNA analyses; 3 were found to have the FMR1 full mutation. None of the 534 children tested positive for the FMR2 full mutation; however, 3 children had unusually small FMR2 alleles suggestive of FMR2 deletions. Screening for fragile X among language-delayed preschoolers is warranted, particularly when there is a family history of mental retardation, but regardless 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 worthy of continued exploration.
Mazzocco
M M
MM
Behavioral Neurogenetics Research Center, Kennedy Krieger Institute, Baltimore, Maryland 21205, USA.
Myers
G F
GF
Hamner
J L
JL
Panoscha
R
R
Shapiro
B K
BK
Reiss
A L
AL
D015139:Blotting, Southern; D002675:Child, Preschool; D005260:Female; D005600:Fragile X Syndrome / Q000150:complications* / Q000175:diagnosis / Q000453:epidemiology / Q000235:genetics*; D006801:Humans; D007223:Infant; D007805:Language Development Disorders / Q000209:etiology* / Q000235:genetics; D008297:Male; D009154:Mutation; D010641:Phenotype; D016133:Polymerase Chain Reaction; D015995:Prevalence; D019680:Trinucleotide Repeat Expansion