A 19-year-old man is evaluated for infertility and gynecomastia. He is tall, with long limbs and small, firm testes. Semen analysis shows azoospermia. Hormone profile shows low testosterone with markedly elevated FSH and LH. Which karyotype is expected?
- A 45,X
- B 47,XXY ✓
- C 47,XYY
- D 46,XX male phenotype
Correct answer: B. 47,XXY
Explanation
The combination of hypergonadotropic hypogonadism, azoospermia, small firm testes, gynecomastia and eunuchoid proportions defines Klinefelter syndrome, classically 47,XXY. The presence of an X chromosome means sex chromatin (a Barr body) is detectable, unlike in 46,XY males. Testicular atrophy results from hyalinization of seminiferous tubules, which explains the high FSH and LH with azoospermia.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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