XXY

Klinefelter syndrome, also called 47,XXY, is a chromosomal condition which results from the presence of an extra X chromosome in cells affecting development in people who are assigned male at birth. The signs and symptoms of Klinefelter syndrome vary. In some cases, the features are so mild that the condition is not diagnosed until puberty or adulthood. Researchers believe that up to 65 percent of people with Klinefelter syndrome are never diagnosed.

“Klinefelter syndrome (47,XXY or KS), is a chromosomal condition which results from the presence of an extra X chromosome in cells.”

Individuals with Klinefelter syndrome typically have small testes that produce a reduced amount of testosterone (primary testicular insufficiency).