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For further information, see CMDT Part 42-22: Klinefelter Syndrome

KEY FEATURES

  • Males with 1 extra X chromosome (XXY)

  • Tall stature, gynecomastia, atrophic testes, infertility

CLINICAL FINDINGS

  • Boys are normal in appearance before puberty; after puberty, they have disproportionately long legs and arms, sparse body hair, a female escutcheon, gynecomastia, and small testes

  • Infertility resulting from azoospermia; the seminiferous tubules are hyalinized

  • Intellectual disability is somewhat more common than in the general population, and many have language-based learning problems

  • Higher risk of osteoporosis, breast cancer, deep venous thrombosis, and diabetes mellitus

DIAGNOSIS

  • Low serum testosterone

  • Karyotype is typically 47, XXY but other sex chromosome anomalies cause variations of Klinefelter syndrome

  • Diagnosis often not made until a man is evaluated for inability to conceive

  • Screening for cancer (especially of the breast), deep venous thrombosis, and glucose intolerance is indicated

TREATMENT

  • Testosterone administration is advisable after puberty but will not restore fertility

  • Mature sperm can be aspirated from the testes and injected into oocytes, resulting in fertilization; there is an increased risk for aneuploidy in sperm, however, and genomic analysis of a blastocyst should be considered before implantation

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