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Klinefelter's syndrome
47, XXY karyotype
Epidemiology:
- occurs in 1/400-700 men
Pathology:
1) failure of the seminiferous tubules
2) azoospermia
3) diminished testosterone production following onset of seminiferous tubular failure
4) excessive production of estradiol by Leydig cells
5) estradiol increases serum testosterone estrone-binding globulin elevated total serum testosterone
Genetics: 47, XXY karyotype
Clinical manifestations:
- tall stature
- gynecomastia
- testicular failure
- hypogonadism
- sexual dysfunction
- decreased sexual hair
- decreased muscle mass [1]
- fatigue [1]
Laboratory:
1) elevated serum FSH
2) serum LH may be elevated
3) serum testostenone may be low or normal
4) serum free testosterone is generally low
5) semen analysis for azoospermia
6) karyotyping
Management:
- fertility may be achieved with ejaculated sperm
- some couples opt for preimplantation genetic testing & embryo biopsy to avoid transmitting the disorder to offspring
- after fertility issues resolved exogenous androgens may be considered to prevent osteoporosis
- oral testosterone undecanoate (Jatenzo) FDA-approved [3]
Related
XX male syndrome; de la Chapelle syndrome
General
genetic syndrome (multisystem disorder)
References
- Medical Knowledge Self Assessment Program (MKSAP) 11, 17, 19.
American College of Physicians, Philadelphia 1998, 2015, 2022
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 380
- FDA News Release. March 27, 2019
FDA approves new oral testosterone capsule for treatment of men
with certain forms of hypogonadism.
https://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm634585.htm