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

Abstract

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.