MOLECULAR-CLINICAL CORRELATIONS IN CHILDREN AND ADULTS WITH FRAGILE X-SYNDROME

Introduction.-Fragile X syndrome is the most commonly known inherited form of mental retardation. The intellectual abilities range from a no rmal IQ with learning disabilities to severe mental retardation. In ma les, there is a tendency for IQ decline in childhood. The purpose of t his study was to correlate variations of the molecular cytosine guanin e guanine (CGG) amplification in the fragile X mental retardation-1 (F MR-1) gene with the clinical findings, including IQ and physical featu res. Methods.-Full-scale IQ and cytogenetic results in 116 individuals with the FMR-1 mutation were studied. The IQ testing was performed wi th age-appropriate standardized tests. Physical features were summariz ed in a physical index score for each patient. The FMR-1 results were determined with the OXI.9 probe and the following system was used: P1 indicates premutation; P2, large premutation to small full mutation; P 3, full mutation; and P4, mosaic. Results/Conclusions.-The findings sh owed that those females with a small insert in the P1 range had a sign ificantly higher IQ than other heterozygotes (P2, P3, and P4 categorie s). P4 males had a significantly higher IQ than P2 or P3 males. In cro ss-sectional age comparisons, the slope of the IQ decline was greater in P2 males than