Klinefelter's syndrome

n. (Genetics) XXY syndrome, disorder in males caused by the presence of an extra X chromosome (characterized by small testicles, decreased sperm production, gynecomastia, long legs and mental retardation)

Not to be confused with XYY syndrome or XXX syndrome. For the Lucía Puenzo film, see XXY (film). Klinefelter's syndrome, 47, XXY or XXY syndrome is a condition caused by a chromosome aneuploidy. Affected males have an extra X sex chromosome. The principal effect is small testes development and reduced fertility. A variety of other physical and behavioral differences and problems are common, though severity varies and many boys and men with the condition have few detectable symptoms. It is the second most common extra chromosome condition, and is named after Dr. Harry Klinefelter, an endocrinologist at Massachusetts General Hospital, Boston, Massachusetts, who first described it in 1942. The condition exists in roughly 1 out of every 500 to 1,000 males.
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Noun
1. syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced sperm production and mental retardation; a genetic defect in which an extra X chromosome (XXY) is present in the male
(synonym) Klinefelter's syndrome, XXY-syndrome
(hypernym) syndrome

Noun
1. syndrome in males that is characterized by small testes and long legs and enlarged breasts and reduced sperm production and mental retardation; a genetic defect in which an extra X chromosome (XXY) is present in the male
(synonym) Klinefelter syndrome, XXY-syndrome
(hypernym) syndrome

A genetic disorder in males caused by having an extra X chromosome. Males with this disorder may have larger than normal breasts, a lack of facial and body hair, a rounded body type, and small testicles. They may learn to speak much later than other children and may have difficulty learning to read and write. Klinefelter's syndrome increases the risk of developing testicular cancer.

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Sex=Male
Chromosome karyotype
47,XXY
(or XXYY)
There is an extra X chromosome or an extra X and Y chromosome
Incidence and risks
1:1000 births (more in sons of older mothers)
Clinical features:
*Decreased crown-pubis:pubis-heel ratio
*eunuchoid testicular atrophy
*Infertility
*Gynaecomastia
*Learning defficulties(20%;related to numbers of X chromosomes)