Cognitive and visual processing skills and their relationship to mutation size in full and premutation female fragile X carriers.

BACKGROUND The fragile X gene contains an unstable trinucleotide (CGG) repeat that expands as it is passed from female carriers to the affected offspring. Obligate female carriers may have a premutation or full mutation genotype. METHODS In this study, fragile X premutation and full mutation female carriers were compared on three tasks of visual processing and cognitive skills. RESULTS In each case, there were significant differences between premutation and full mutation carriers on a number of the subtests or the full test scores. Specifically, full mutation female carriers performed more poorly in visual-motor processing and analysis-synthesis on the Woodcock-Johnson Psycho-Educational Battery-Revised, The Developmental Test of Visual Motor Integration, and on five of the seven subtests of the Test of Visual-Perceptual Skills. Regression analyses revealed significant negative correlations between mutation size and cognitive ability. CONCLUSIONS These findings have implications in educational planning decisions for full mutation carriers who may present with specific cognitive deficits.