Down Syndrome and Dementia — MRCPsych Paper B MCQ

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ModerateIntellectual DisabilityDown Syndrome and DementiaMRCPsych Paper B

A 48-year-old man with Down syndrome has developed progressive memory impairment, apathy and loss of previously established self-care skills over 3 years. He has recently developed generalised myoclonic and tonic-clonic seizures. There are no focal neurological signs, and the decline has not been stepwise. What is the most likely underlying neurodegenerative diagnosis?

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Correct answer: D — Early-onset Alzheimer's disease

The diagnosis is **early-onset Alzheimer's disease**. Adults with Down syndrome have a particularly high risk of Alzheimer's dementia, often developing symptomatic disease decades earlier than the general population. The progressive decline from established cognitive and adaptive functioning, together with new late-onset myoclonic or generalised seizures, is characteristic of Down syndrome-associated Alzheimer's disease. Vascular dementia is less likely without a stepwise course or focal neurological findings. Frontotemporal dementia may cause early behavioural change but is less strongly associated with Down syndrome and does not best explain this combined pattern. Creutzfeldt-Jakob disease typically progresses rapidly over weeks or months rather than 3 years. Normal ageing does not cause progressive loss of established self-care skills or new seizures.

Reference: Altuna M, Giménez S, Fortea J. Epilepsy in Down Syndrome: A Highly Prevalent Comorbidity. Journal of Clinical Medicine. 2021;10(13):2776. https://pubmed.ncbi.nlm.nih.gov/34202784/