A 17-year-old boy is evaluated for delayed puberty and gynecomastia. He is tall with an arm span greater than height, sparse facial hair, and small firm testes. Semen analysis shows azoospermia. Which finding is expected on chromosomal analysis?
- A 47,XXY ✓
- B 45,X/46,XY mosaicism
- C 47,XYY
- D 46,XX male with SRY translocation
Correct answer: A. 47,XXY
Explanation
Klinefelter syndrome (47,XXY) is the most common cause of primary testicular failure in males. It presents after puberty with tall eunuchoid build, gynecomastia, small firm testes, azoospermia, and elevated gonadotropins with low testosterone. The extra X chromosome causes hyalinization of seminiferous tubules and Leydig cell dysfunction. 45,X occurs in phenotypic females, 47,XYY males are typically tall but fertile, and XX maleness is far rarer with normal-sized testes absent in most descriptions.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.