A 28-year-old male on haloperidol for schizophrenia presents with temperature 40.2°C, lead-pipe rigidity, diaphoresis, and creatine kinase of 12,000 U/L. His consciousness is clouded. Which receptor mechanism is primarily responsible for this syndrome?

• A Serotonin 5-HT2A receptor overstimulation
• B Cholinergic muscarinic receptor blockade
• C GABA-A receptor inhibition
• D Dopamine D2 receptor blockade in the hypothalamus and striatum ✓

Explanation

Neuroleptic Malignant Syndrome (NMS) results from acute central dopamine D2 receptor blockade, particularly in the hypothalamus (causing hyperthermia and autonomic instability) and striatum (causing rigidity). Serotonin syndrome involves 5-HT overstimulation, presenting with clonus and hyperreflexia rather than lead-pipe rigidity. Muscarinic blockade causes anticholinergic toxidrome. GABA-A inhibition is not the mechanism.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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