++
For further information, see CMDT Part 42-22: Klinefelter Syndrome
++
Males with 1 extra X chromosome (XXY)
Tall stature, gynecomastia, atrophic testes, infertility
++
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
++
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
++
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