A 16-year-old boy is evaluated for gynaecomastia and absence of secondary sexual characteristics. He is tall with long limbs, small firm testes, and sparse facial hair. Semen analysis shows azoospermia. Which karyotype is most likely?
- A 45,X
- B 47,XXY ✓
- C 47,XYY
- D 46,XX male
Correct answer: B. 47,XXY
Explanation
Klinefelter syndrome (47,XXY) presents after puberty with tall stature, eunuchoid proportions, gynaecomastia, small firm testes, hypergonadotropic hypogonadism and azoospermia due to hyalinised seminiferous tubules. 45,X is female Turner syndrome. 47,XYY males are typically tall but fertile with normal testicular function. XX maleness arises from SRY translocation and does not produce this classic phenotype.
Reference: Nelson Textbook of Pediatrics, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.