Molecular-clinical correlations in children and adults with fragile X syndrome.
BACKGROUND
Fragile X syndrome is the most commonly known inherited form of mental retardation. The intellectual abilities range from a normal IQ with learning disabilities to severe mental retardation. In males, there is a tendency for IQ decline in childhood. The purpose of this study was to correlate variations of the molecular cytosine guanine guanine (CGG) amplification in the fragile X mental retardation-1 (FMR-1) gene with the clinical findings, including IQ and physical features.


METHODS
Full-scale IQ and cytogenetic results in 116 individuals with the FMR-1 mutation were studied. The IQ testing was performed with age-appropriate standardized tests. Physical features were summarized in a physical index score for each patient. The FMR-1 results were determined with the OX1.9 probe and the following system was used: P1 indicates premutation; P2, large premutation to small full mutation; P3, full mutation; and P4, mosaic.


CONCLUSIONS
The findings showed that those females with a small insert in the P1 range had a significantly higher IQ than other heterozygotes (P2, P3, and P4 categories). P4 males had a significantly higher IQ than P2 or P3 males. In cross-sectional age comparisons, the slope of the IQ decline was greater in P2 males than in P4 or P3 males.
Staley
L W
LW
Child Development Unit, Children's Hospital, Denver, CO 80218.
Hull
C E
CE
Mazzocco
M M
MM
Thibodeau
S N
SN
Snow
K
K
Wilson
V L
VL
Taylor
A
A
McGavran
L
L
Weiner
D
D
Riddle
J
J
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D005260:Female; D005600:Fragile X Syndrome / Q000235:genetics*; D005784:Gene Amplification; D006801:Humans; D007223:Infant; D008607:Intellectual Disability / Q000235:genetics*; D007361:Intelligence Tests; D008297:Male; D008875:Middle Aged; D008967:Molecular Biology; D010641:Phenotype; D012737:Sex Factors