Prader-Willi syndrome — RACP Paediatrics MCQ

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HardGeneticsPrader-Willi syndromeRACP Paediatrics

A 4-year-old presents with hypotonia, obesity, short stature, hypogonadism, and insatiable appetite. He had severe neonatal hypotonia and feeding difficulties. What is the most appropriate genetic investigation?

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Correct answer: E — Methylation studies

The presentation of neonatal hypotonia followed by hyperphagia, obesity, short stature, and hypogonadism is classic Prader-Willi syndrome. DNA methylation analysis at chromosome 15q11.2 is the first-line diagnostic test, detecting >99% of cases regardless of the underlying mechanism (deletion, UPD, or imprinting defect). Standard karyotype and CMA may miss some mechanisms.

Reference: RACP Paediatric Curriculum – Genetics; RCH Melbourne – 2023 – Prader-Willi Syndrome CPG