An association of FRAXE expression with concurrent methylation of the CpG island and mild non-specific mental handicap in males has been reported by several groups.
The cytogenetic expression of the folate sensitive fragile site, FRAXE, is due to the expansion of a GCC repeat in proximal Xq28 of the human X chromosome and is associated with a mild form of mental handicap.
The cytogenetic expression of FRAXE is thought to be associated with mental handicap, but this is usually mild compared to that of the more common fragile X syndrome that is associated with the expression of the FRAXA fragile site.
A relationship between FRAXE and non-specific mental impairment is strongly suggested by the occurrence in these families of more mentally impaired male and female carriers, after removal of index cases, than could reasonably be expected by chance.
The expression of FRAXA is associated with the fragile X syndrome, the most prevalent form of inherited mental retardation whilst the expression of FRAXE is associated with a rarer and comparatively milder form of mental handicap.