Neuropsychological profiles of three sisters homozygous for the fragile X premutation.

Fragile X syndrome (fraX) is associated with an amplification of a CGG repeat within the fraX mental retardation (FMR-1) gene. We describe an exceptional family in which 3 adult sisters are homozygous for the FMR-1 premutation. Each sister inherited 2 premutation alleles (ca. 80 CGG repeats) from their biologically unrelated parents. The 3 sisters were administered measures of executive function, visual spatial, memory, and verbal skills. Deficiencies in the first 2 of these domains have been reported among females with the full mutation. The sisters' performances were compared with available normative data and with published group means for females affected by fraX. These women did not appear to have verbal or memory difficulties. None of the women demonstrated a global executive function deficit, and none had global deficits in spatial ability. The profiles of these sisters are consistent with reports that the fragile X premutation does not affect cognitive performance.