By Hidaya Aliouche, B.Sc.Reviewed by Dr. Jennifer Logan, MD, MPH Superman syndrome, also known as 47, XYY, is a condition classified as a chromosomal aneuploidy (which is an abnormality in chromosome structure and/or number) in which males have an additional Y chromosome. Image Credit: Rost9 / Shutterstock.com The normal male sex chromosomes are XY; in the case...