Klinefelter syndrome

Klinefelter syndrome
Other names	XXY syndrome, Klinefelter's syndrome, Klinefelter-Reifenstein-Albright syndrome
47,XXY karyotype
Pronunciation	/ˈklaɪnfɛltər/
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[1]
Complications	Infertility, intellectual disability,[2] autoimmune disorders, breast cancer, venous thromboembolic disease, osteoporosis
Usual onset	At fertilisation[3]
Duration	Lifelong
Causes	Nondisjunction during gametogenesis or in a zygote[4]
Risk factors	Older age of mother[5]
Diagnostic method	Genetic testing (karyotype)[6]
Prevention	None
Treatment	Physical therapy, speech and language therapy, Testosterone Supplementation, counseling[7]
Prognosis	Nearly normal life expectancy[8]
Frequency	1 in 500–1000[5][9]
Named after	Harry Klinefelter

Klinefelter syndrome (KS), also known as 47,XXY, is a chromosome anomaly where a male has an extra X chromosome.^[10] 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, along with his colleagues at Massachusetts General Hospital.^{[4][5][11][12]}

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 karyotyping.^{[4][6][13][14]}