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Klinefelter Syndrome

Review literature: (Lanfranco et al., 2004).

Definition of Klinefelter Syndrome

Klinefelter syndrome is the most common sex chromosome disorder and results in primary hypogonadism and infertility in men. The syndrome is caused by an additional X chromosomes resulting in a karyotype of 47,XXY.

Synonyms: XXY syndrome, 47,XXY males,

Epidemiology of Klinefelter Syndrome

Prevalence in men 1:500–1000, less than 50% of affected patients are diagnosed.

Causes (Etiology) and Pathology of Klinefelter Syndrome

The karyotype of Klinefelter syndrome is 47,XXY. Also possible karyotypes are 46,XY/47,XXY mosaic. The cause of the sex chromosome disorder is a defect of meiosis during gametogenesis, meiotic defects of the zygote cause Klinefelter syndrome with mosaic karyotype.

Klinefelter syndrome results in a sclerosis of the seminiferous tubules, missing or severely damaged spermatogenesis and hyperplasia of Leydig cells.

Signs and Symptoms

• Male phenotype
• Before puberty, small testes and disproportionately long legs are present. The verbal IQ might be reduced.
• After puberty, signs of androgen deficiency develop (infertility, decreased virilization, small penis, low muscle mass), in addition small firm testes, gynecomastia, and an increased body length (75th percentile in average).
• Untreated adults develop osteoporosis, they have an increased risk of diabetes mellitus, varicosis, breast cancer, lung disease and extragonadal germ cell tumors.

Diagnostic Workup in Klinefelter Syndrome

Klinefelter syndrome should be suspected if azoospermia, hypergonadotropic hypogonadism and the above mentioned phenotype are present.

• Laboratory tests: FSH, testosterone
• Sperm count (azoospermia) and testicular biopsy (seminiferous tubular sclerosis)
• Testicular ultrasound examination
• Barr body analysis
• Karyotyping of lymphocytes

Treatment of Klinefelter Syndrome

• Testosterone treatment with the onset of puberty promotes secondary male sex characteristics, reduction of gynecomastia and prevents osteoporosis.
• ICSI with IVF is an option in patients mosaic Klinefelter syndrome with oligospermia
• Testicular sperm extraction has been reported in nonmosaic Klinefelter syndrome

References

  Deutsche Version: Klinefelter-Syndrom