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CAR: Anomalies - Chromosome
Klinefelter Syndrome

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    Triple X
    YY syndrome


Introduction Antenatal Postnatal West Midlands Data


Klinefelter syndrome occurs in males as a result of one or more additional X chromosomes. Instead of the usual (diploid) male karyotype 46XY, the karyotype for Klinefelter syndrome can be 47XXY, 48XXXY, or 49XXXXY.

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There are no distinguishing features of Klinefelter syndrome on ultrasound although cystic hygroma have been reported in some cases.

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Affected males are usually tall with relatively long limbs and poor muscle development. Pubertal development is normal but testicular size decreases after puberty (hypogonadism) and many cases remain undiagnosed until this time. Males suffer from azoospermia and are therefore infertile. The development of secondary sexual characteristics is also affected. Boys can exhibit gynaecomastia (male breasts resembling female) and the risk of breast cancer is the same as for females. Although sexual function is normal libido and sexual activity are reduced and beard growth is minimal. Testosterone levels may be reduced and levels of follicle stimulating hormone gonadotrophin and are increased. Children can be treated with testosterone before school age.

Life span is not reduced and IQs are within normal range. However, there is some evidence to suggest that intellectual development is delayed and individuals have some educational difficulties and behavioural problems.

Those with the rarer karyotypes 48XXXY, or 49XXXXY are more severely affected. Growth deficiency, hypogenitalism, and mental retardation are more pronounced. With karyotype 49XXXXY, infants are severely mentally retarded. Facial features include hypertelorism, epicanthic folds, a broad nose, and a large open mouth. Other associated skeletal anomalies include radio-ulnar synostosis at the elbow and clinodactyly.

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To be added

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© Perinatal Institute 2011