<unk>  is a sex chromosome anomaly in which males have an extra X and Y chromosome. Human cells usually contain two sex chromosomes, one from the mother and one from the father. Usually, females have two X chromosomes (XX) and males have one X and one Y chromosome (XY). The appearance of at least one Y chromosome with a properly functioning SRY gene makes a male. Therefore, humans with<unk>  are genotypically male. Males with<unk>  have 48 chromosomes instead of the typical 46. This is why<unk>  is sometimes written as 48,XXYY syndrome or 48,XXYY. It affects an estimated one in every 18,000–40,000 male births.
XXYY syndrome
XYYY syndrome
XXXXY syndrome
XYYYY syndrome
XX male syndrome
XXXY syndrome
Ring chromosome 20 syndrome
Joubert syndrome