Previously known to be a variant or type of the Klinefelter's syndrome, this condition is an anomaly of the sex chromosome. The features usually include gynecomastia (having enlarged male breasts), ulcers of the skin, deformed craniofacial features, and being unusually tall. It is also believed to affect 1 in every 17,000 male babies that are born. XXYY is just one of the many variations of chromosomal defects which include the following: 47 xxy, xy, xxxxy, and xxxy; also the xyy. These syndromes affect males whereas female counterparts include the Turner syndrome and other varieties with added X chromosomes.




It is still not fully understood what causes the xxyy syndrome. Studies of the condition are very limited and currently, there is but little information as to the origin of this syndrome. It is still not known whether the it is the environment or merely the chromosomal activities which are factors to the development of this syndrome. It is good to note, though, that parents who have one child with xxyy syndrome are bound to have more kids with the same condition.


Karyotyping is necessary to be able to diagnose xxyy. Karyotyping is done by drawing some blood and studying the blood sample to see if xxyy is present on the boy's chromosomal structure. This is the only known test that can reveal xxyy syndrome.