Tetrasomy X (also called XXXX syndrome, quadruple X, or 48,XXXX) is an extremely rare chromosomal disorder caused by the presence of four X chromosomes instead of two X chromosomes.This condition occurs only in females, as there are no Y chromosomes present that could trigger male development.
Tetrasomy X was first described in 1961, and since then approximately 100 cases have been reported worldwide. [Source: Wikipedia ]