Chromosomal abnormalities · USMLE Step 1

A teenager with tall stature, small testes, gynecomastia, and reduced facial hair undergoes genetic testing. The likely result is:

  1. 47,XYY
  2. 47,XXY
  3. 45,X
  4. 46,XX deletion
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Correct answer: 47,XXY

Klinefelter syndrome (47,XXY) presents with tall stature, small testes, and gynecomastia due to hypogonadism. The extra X chromosome leads to impaired sexual development. XYY males generally have normal sexual development.

Difficulty: Medium Question 5 of 20

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