NEUROPSYCHOLOGICAL PROFILES OF 3 SISTERS HOMOZYGOUS FOR THE FRAGILE-XPREMUTATION

Fragile X syndrome (fraX) is associated with an amplification of a CGG repeat within the fraX mental retardation (FMR-1) gene. We describe a n exceptional family in which 3 adult sisters are homozygous for the F MR-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, memo ry, and verbal skills. Deficiencies in the first 2 of these domains ha ve been reported among females with the full mutation. The sisters' pe rformances were compared with available normative data and with publis hed group means for females affected by fraX. These women did not appe ar to have verbal or memory difficulties. None of the women demonstrat ed a global executive function deficit, and none had global deficits i n spatial ability. The profiles of these sisters are consistent with r eports that the fragile X premutation does not affect cognitive perfor mance. (C) 1996 Wiley-Liss, Inc.