Klinefelter syndrome

Signs and Symptoms

Males are often infertile and tend to have less muscular growth. Through puberty they tend to have less muscles through their life.


The extra X chromosome is retained because of a nondisjunction event during meiosis . Nondisjunction occurs when homologous chromosomes, in this case the X and Y sex chromosomes, fail to separate, producing a sperm with an X and a Y chromosome. Fertilizing a normal (X) egg produces an XXY offspring. The XXY chromosome arrangement is one of the most common genetic variations from the XY, occurring in about 1 in 500 live male births.


Long term effects include muscular growth and development as well as reading and motor development.


This genetic disorder is irreversible.

Additional info

Children with XXY differ little from other children. Although they can face problems during adolescence, often emotional and behavioural, and difficulties at school, most of them can achieve full independence from their families in adulthood. Most can lead a normal, healthy life.

The results of a study carried out on 87 Australian adults with the syndrome shows that those who have had a diagnosis and appropriate treatment from a very young age had a significant benefit with respect to those who had been diagnosed in adulthood.