An 80-year-old woman with Parkinson's disease develops visual hallucinations of small animals and children in her room. Her cognition fluctuates significantly day-to-day. She is unusually sensitive to haloperidol. What is the MOST likely diagnosis?

• A Vascular dementia
• B Alzheimer's disease with psychosis
• C Dementia with Lewy bodies (DLB) ✓
• D Delirium due to urinary tract infection

Explanation

Dementia with Lewy bodies (DLB) is characterised by the triad of: (1) fluctuating cognition with pronounced variation in attention and alertness, (2) recurrent vivid visual hallucinations (typically of people or animals), and (3) spontaneous parkinsonism. Severe neuroleptic sensitivity (marked rigidity, sedation, accelerated cognitive decline with haloperidol or other D2-blocking antipsychotics) is a core feature that can be life-threatening. Quetiapine or clozapine at low doses are the preferred antipsychotics if necessary. Rivastigmine has evidence for cognitive symptoms in DLB.

Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.

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Written and medically reviewed by the StethoPrep medical team.