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

• Mental retardation is somewhat more common than in the general population, and many have learning problems

• Higher risk of osteoporosis, breast cancer, and diabetes mellitus

Diagnosis

• Low serum testosterone

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

• 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

• Intracytoplasmic sperm injection is possible using sperm obtained by testicular extraction