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Delirium due to infection — MCCQE Part 1 MCQ

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EasyDeliriumDelirium due to infectionMCCQE Part 1

A 72-year-old man is admitted with pneumonia and becomes acutely inattentive overnight. He fluctuates between agitation and somnolence, sees insects on the wall, and cannot recite months backward. His daughter says he was independent last week. What is the most likely diagnosis?

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Correct answer: C — Delirium

Acute fluctuating inattention with altered arousal and perceptual disturbance in the context of infection is delirium. Alzheimer disease is typically insidious and progressive rather than overnight. Depression can impair concentration but does not usually cause fluctuating consciousness. Normal ageing does not cause acute hallucinations and inattention.

Reference: CCSMH delirium guidelines