Klinefelter's syndrome Dr Trisha Macnair Tall stature is a typical feature of this genetic condition affecting men.

In this article

What is Klinefelter’s syndrome? Symptoms

Causes and risk factors Treatment and recovery

Klinefelter's syndrome is a chromosomal abnormality that affects males who carry an extra one or more X chromosomes. Females have XX chromosomes and males have XY chromosomes. A male with Klinefelter’s would have XXY or XXXY. It can lead to a variety of physical and physiological characteristics.

Features vary from person to person and are not usually apparent until puberty. Some males may not have any symptoms at all. Typical features include tall stature (with disproportionately long legs and arms), pear-shaped fat distribution and delayed puberty.

There may be signs of feminisation such as small or undescended testes, scant body hair and breast development. Infertility and lack of libido are also common.

Mild developmental and behavioural problems are common. There are also links to thyroid problems, diabetes and osteoporosis and there is an increased risk of breast cancer.

The condition is thought to affect between one in 600 newborn males in the UK. Cases are sporadic but there's an increased risk in the children of older mothers. Older mothers at risk may be offered pre-natal tests.

There's currently no cure, but testosterone replacement therapy may induce a more male appearance and reduce the risk of osteoporosis in many cases. Fertility can often be accomplished with fertility treatment.

This article was last medically reviewed by Dr Trisha Macnair in November 2009.