What are the sexual characteristics in Klinefelter syndrome?

Updated: Mar 23, 2020
  • Author: Germaine L Defendi, MD, MS, FAAP; Chief Editor: Luis O Rohena, MD, MS, FAAP, FACMG  more...
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Genital abnormalities are not commonly observed in 47,XXY males. This is an important observation because Klinefelter syndrome is considered a cause of genital abnormality or ambiguity. [26]  The genital phenotype can include complete sex reversal, true hermaphroditism (eg, ovotestes), testicular feminization, and ambiguous genitalia/undervirilization (eg, hypospadiasmicropenis, epispadias, female external genitalia).

Pubertal changes with lack of secondary sexual characteristics are due to decreased androgen production. This results in sparse facial, body, or sexual hair; a high-pitched voice; and body fat distribution as is observed in females. By late puberty, 30-50% of boys with Klinefelter syndrome present with gynecomastia, which is due to elevated estradiol levels and an increased estradiol:testosterone ratio. The risk of developing breast carcinoma in Klinefelter syndrome is at least 20 times higher than in healthy individuals. There is also an increased risk of extragonadal germ cell tumors such as embryonal carcinoma, teratoma, and primary mediastinal germ cell tumor.

Postpubertal males may have testicular dysgenesis (small firm testis; testis size < 10 mL). Infertility, azoospermia, or both may result from atrophy of the seminiferous tubules. Most males with a 47,XXY karyotype are infertile, but patients with Klinefelter syndrome mosaicism (46,XY/47,XXY) can be fertile. Guidelines for the assessment and treatment of people with fertility problems have been established. [27]

A literature review by Deebel et al indicated that, while azoospermia is a characteristic of Klinefelter syndrome, patients are frequently positive for spermatogonia. Indeed, spermatogonial cells were found in 100% of fetal/infantile patients and in 83%, 42.7%, and 48.5% of prepubertal, peripubertal, and adult patients. In addition, positive spermatogonia results were found in 46.4% of peripubertal/adolescent patients and 24.3% of adult patients, who were negative for spermatozoa. [28]

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