A 70-year-old man develops fluctuating cognition, recurrent visual hallucinations of small animals, mild parkinsonism, and REM sleep behaviour disorder. His symptoms are exacerbated by low-dose haloperidol given for the hallucinations, causing severe rigidity. The most likely diagnosis is:
- A Dementia with Lewy Bodies (DLB) ✓
- B Alzheimer's Disease with Psychosis
- C Vascular Dementia
- D Parkinson's Disease Dementia
Explanation
The clinical triad of Dementia with Lewy Bodies comprises: fluctuating cognition, recurrent well-formed visual hallucinations, and spontaneous features of parkinsonism. REM sleep behaviour disorder (RBD) is a core clinical feature in DSM-5 and an early biomarker. The critical diagnostic and management point is severe neuroleptic sensitivity — DLB patients develop marked rigidity, autonomic instability, and even fatal neuroleptic malignant syndrome-like reactions with conventional antipsychotics (haloperidol). This sensitivity is attributed to severe striatal dopaminergic depletion. Clozapine or quetiapine in low doses are preferred if antipsychotics are absolutely necessary.
Reference: Kaplan & Sadock's Synopsis of Psychiatry, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.