emain undiagnosed. Symptoms depend on the proportion of cells in the body that contain an extra X chromosome (XXY), how much testosterone is being produced and the age at diagnosis.
From early school age, boys with Klinefelter’s syndrome tend to be taller (increased leg length) and may have reduced coordination compared with other boys. This increase in height is maintained throughout life.
From the time of puberty, most affected boys fail to make as much testosterone as unaffected boys. This can lead to a taller, less muscular appearance with less facial and body hair; impaired sex drive (libido) and difficulties maintaining erections (potency); and lower energy levels. Men with Klinefelter’s syndrome may develop breast enlargement (gynaecomastia) and thinning of the bones (osteoporosis). Characteristically, they have small, firm testes with a low or absent sperm count; almost all men who are 47 XXY will be infertile. However, most men with Klinefelter’s syndrome may have a normal sex life.
A significant proportion of men with Klinefelter’s syndrome have some kind of difficulties with language (problems reading or learning to talk initially) or executive functions (problem solving, task switching, planning etc) not dissimilar to people with dyslexia. They may also have trouble with social interactions throughout life, but particularly in childhood. The majority of men with Klinefelter’s syndrome lead an independent life, forming relationships and getting a normal job and have a normal life span.
How common is Klinefelter’s syndrome?
Klinefelter’s syndrome only affects men. It is one of the most common chromosome abnormalities in men. About one of every 650 live male births has an extra X chromosome, but many do not have any symptoms. Importantly, up to 3% of infertile men have Klinefelter’s syndrome.
Is Klinefelter’s syndrome inherited?
Klinefelter’s syndrome is a genetic condition but it is not inherited from the parents. In the vast majority of boys, there are no other affected family members; it occurs sporadically. The extra X chromosome can come from either the mother or the father. It is thought that older parents may be more likely to have a child with Klinefelter’s syndrome; this is probably because the risk of chromosomal abnormalities increases with age.
How is Klinefelter’s syndrome diagnosed?
Where Klinefelter’s syndrome is suspected, blood tests will be carried out to assess levels of testosterone and gonadotrophins (luteinising hormone and follicle stimulating hormone). In patients with Klinefelter’s syndrome, blood tests characteristically show a low testosterone level, high sex hormone binding globulin (SHBG) and raised gonadotrophins.
The diagnosis of Klinefelter’s syndrome is confirmed by chromosomal analysis (karyotyping), which involves a blood test. This is usually carried out as an outpatient.
Karyotyping can also be performed during pregnancy by analysing the fluid surrounding the foetus (amniocentesis) or by obtaining placental tissue (chorionic villus sampling). Both these procedures carry some risk and are performed as an inpatient.
How is Klinefelter’s syndrome treated?
The underlying chromosomal problem (XXY) cannot be changed, so the aim of treatment is to help with symptoms and prevent complications in the long-term. Early identification of affected individuals is therefore helpful. Treatment will differ among individuals depending on their age at diagnosis and level of symptoms experienced.
Testosterone replacement therapy is important where levels are low, and may be required from the start of puberty. The dose is adjusted to maintain appropriate testosterone concentrations. Testosterone can be given in a number of ways but is usually given by gel, which is rubbed onto the skin every day, or by injection. This is done as an outpatient.
Testosterone replacement therapy helps to improve testosterone levels in order to aid muscle development, facial and body hair growth, and sex drive. It also helps to improve self-esteem, mood and maintain bone health. In addition, some men with Klinefelter