(47 XXY Syndrome; KS)
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Klinefelter syndrome (KS) occurs in some men who have more than one X chromosome (XXY).
Males usually inherit a single X chromosome from their mother and a single Y chromosome from their father. Males with KS get at least one extra X chromosome.
A risk factor is something that increases your chance of KS. Women over age 35 may have a slightly increased chance of having a child with KS. There are no other known risk factors for this disorder.
XXY occurs in approximately 1 out of 580 live male births, but many men with it do not develop KS. When KS does develop, it usually goes undetected until puberty or sometimes much later.
Characteristics may include:
- For babies: Smaller birth weight and slower muscle and motor development
For children and adults:
- Small firm testes, small penis
- Abnormal body proportions (long legs, short trunk)
- Tallness with extra long arms and legs
- Social and learning disabilities (common)
- Personality impairment
- Attention deficit hyperactivity disorder (ADHD)
- Speech and language problems—Children with KS often learn to speak later than other children do. They may have a difficult time reading and writing.
- Normal to borderline IQ
- Lack of ability to produce sperm (common)
- Lack of facial and body hair
- Enlarged breasts (common)
- Diminished sex drive, sexual dysfunction
Men with KS have an increased risk of:
A test called a karyotype is used to diagnose KS. In the case of KS, there are usually 47 chromosomes rather than the normal 46.
Many men with XXY do not know they have the condition. The diagnosis may be found: