GENERAL OVERGROWTH IN THE FRAGILE-X SYNDROME - VARIABILITY IN THE PHENOTYPIC-EXPRESSION OF THE FMR1 GENE MUTATION

The fragile X syndrome, which often presents in childhood with overgro wth, may in some cases show some diagnostic overlap with classical Sot os syndrome. We describe four fragile X patients with general overgrow th, all of whom are from families with other affected relatives who sh ow the classic Martin-Bell phenotype. Molecular studies of the FMR1 ge ne in all cases showed the typical full mutation as seen in males affe cted by the fragile X syndrome. Endocrine studies were unremarkable, e xcept in one case where there were raised levels of insulin-like growt h factor-I (IGF-I) and insulin-like growth factor binding protein-3 (I GFBP-3). These cases illustrate the clinical variability of the fragil e X syndrome and the necessity of performing analysis of the FMR1 gene in mentally retarded patients presenting with general overgrowth.