Chromosomal abnormalities · USMLE Step 1

A child presents with ataxia, seizures, and inappropriate laughter. Genetic testing reveals maternal imprinting defect with paternal uniparental disomy. Which syndrome is most consistent?

  1. Prader-Willi syndrome
  2. Angelman syndrome
  3. Wolf-Hirschhorn syndrome
  4. Williams syndrome
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Correct answer: Angelman syndrome

Angelman syndrome results from loss of maternal UBE3A expression, often due to paternal uniparental disomy or maternal deletion. Clinical features include ataxia and happy demeanor. Prader-Willi involves the paternal genes on the same locus.

Difficulty: Medium Question 17 of 20

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