skip to main content

Prader-Willi methylation abnormality — MRCPCH TAS MCQ

Instant feedback + full explanation. One question, done properly.

HardGeneticsPrader-Willi methylation abnormalityMRCPCH TAS

A 2-year-old boy had severe neonatal hypotonia and poor feeding. He now has rapid weight gain, developmental delay and small hands. What is the most likely genetic mechanism?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Loss of paternal expression at 15q11-q13

Prader-Willi syndrome is caused by absent paternal expression of genes in 15q11-q13, commonly through paternal deletion, maternal uniparental disomy or imprinting defect. Loss of maternal expression in the same region causes Angelman syndrome, typically with severe speech impairment and ataxia. The pearl is that methylation testing can detect the parent-of-origin imprinting abnormality.

Reference: Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi; The Science of Paediatrics MRCPCH Mastercourse