Structural abnormalities can be caused by partial chromosome deletions such as in Wolf–Hirschhorn and Cri-du-chat syndromes caused by partial deletions of the short arm of chromosome 4 and 5, respectively,7 or other chromosome alterations such as in Angelman syndrome (deletions or variants in UBE3A on chromosome 158) and Fragile X syndrome (FXS) (expansion of FMR1 on chromosome X).9 FXS is associated with cognitive deficits and behavioral problems, yet, females are most often compensated by the normal X chromosome and their phenotypes vary substantially.10 This evidence concerns the gene FMR1 and fragile X syndrome.