Prader-Willi Syndrome — MRCPsych Paper B MCQ

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ModerateIntellectual DisabilityPrader-Willi SyndromeMRCPsych Paper B

A 25-year-old woman with Prader-Willi syndrome persistently seeks food immediately after nutritionally adequate meals. She becomes aggressive when staff prevent access to stored food. There have been no recent medication changes. Which mechanism best explains her hyperphagia?

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Correct answer: C — Impaired hypothalamic regulation of hunger and satiety

The correct answer is C. Prader-Willi syndrome results from absent expression of paternally derived genes in chromosome region 15q11–q13. Its hyperphagia reflects disrupted hypothalamic and related neural circuits regulating hunger, energy homeostasis and post-meal satiety. Persistent food-seeking despite adequate intake is therefore part of the syndrome's biological behavioural phenotype. Learning may shape how food is sought but is not the primary cause. A medication effect is unlikely given the absence of medication changes, while anxiety-related eating does not characteristically produce the pervasive lack of satiety seen here. Pica refers to persistent ingestion of non-food substances. Aggression may occur when access to food is restricted but does not itself explain the hyperphagia.

Reference: Correa-da-Silva F, Fliers E, Swaab DF, Yi CX. Hypothalamic neuropeptides and neurocircuitries in Prader Willi syndrome. Journal of Neuroendocrinology. 2021;33:e12994. https://pubmed.ncbi.nlm.nih.gov/34156126/