For example, Fragile XE syndrome (FRAXE), caused by a CGG repeat expansion in the FMR2 gene (Knight et al., 1993; Gu et al., 1996; Gecz et al., 1996), manifests in an X-linked intellectual disability similar to FXS (Mulley et al., 1995; Gecz, 2000). This evidence concerns the gene AFF2 and FRAXE intellectual disability.