A boy aged 14 presents with tall stature, small firm testes, gynecomastia, and reduced body/facial hair. His IQ is borderline normal. Karyotype would most likely show:

• A 47, XYY
• B 46, XX (SRY-positive)
• C 45, X/46, XY mosaicism
• D 47, XXY ✓

Explanation

Klinefelter syndrome (47, XXY) is the most common sex chromosome aneuploidy in males (1:600 live male births). Key features include tall stature, small firm (hyalinized) testes post-puberty, azoospermia and infertility, gynecomastia, reduced facial/body/pubic hair, and a slightly below-average IQ with learning difficulties. FSH and LH are elevated, testosterone is low-to-normal. 47, XYY presents with tall stature but normal testicular function and fertility. 46, XX males (SRY-positive) have phenotypic male features but smaller stature compared to Klinefelter and no tall stature. 45,X/46,XY mosaicism causes mixed gonadal dysgenesis.

Reference: Ghai Essential Pediatrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.