Klinefelter syndrome
Klinefelter syndrome (KS), also known as 47,XXY, is a chromosome anomaly where a boy or man has an extra X chromosome. As the presence of a Y chromosome denotes male sex, people with Klinefelter syndrome are genetically male. These complications commonly include infertility and small, poorly functioning testicles (if present). These symptoms are often noticed only at puberty, although this is one of the most common chromosomal disorders, occurring in one to two per 1,000 live births. It is named after American endocrinologist Harry Klinefelter, who identified the condition in the 1940s.
| Klinefelter syndrome | |
|---|---|
| Other names | XXY syndrome, Klinefelter's syndrome, Klinefelter-Reifenstein-Albright syndrome |
| 47,XXY karyotype | |
| Pronunciation |
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| Specialty | Medical genetics |
| Symptoms | Varied; include above average height, weaker muscles, poor coordination, less body hair, breast growth, small testicle size, less interest in sex, infertility |
| Complications | Infertility, intellectual disability, autoimmune disorders, breast cancer, venous thromboembolic disease, osteoporosis |
| Usual onset | At fertilisation |
| Duration | Lifelong |
| Causes | Two X chromosomes in men |
| Risk factors | Older age of mother |
| Diagnostic method | Genetic testing (karyotype) |
| Prevention | None |
| Treatment | Physical therapy, speech and language therapy, Testosterone Supplementation, counseling |
| Prognosis | Nearly normal life expectancy |
| Frequency | 1 in 500–1000 |
| Named after | Harry Klinefelter |
The syndrome is defined by the presence of at least one extra X chromosome in addition to a Y chromosome yielding a total of 47 or more chromosomes rather than the usual 46. Klinefelter syndrome occurs randomly. The extra X chromosome comes from the father and mother nearly equally. An older mother may have a slightly increased risk of a child with KS. The syndrome is diagnosed by the genetic test known as a karyotype.