Chromosomal abnormalities · USMLE Step 1

A newborn with micrognathia, low-set ears, and clenched fists is diagnosed with Edwards syndrome. What karyotype confirms this condition?

  1. 47,XY,+13
  2. 47,XX,+18
  3. 47,XX,+21
  4. 45,X
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Correct answer: 47,XX,+18

Edwards syndrome is trisomy 18, so the karyotype would show +18. Clinical features include clenched fists and cardiac defects. Other options represent different syndromes.

Difficulty: Medium Question 16 of 20

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