A psychiatric patient receiving haloperidol develops severe 'lead-pipe' muscle rigidity, fever of 40 C, autonomic instability, and serum creatine kinase of 45000 U/L. What is the diagnosis?

Answer and explanation

Correct answer: A. Neuroleptic malignant syndrome

  1. Step 1: Potent dopamine D2-receptor antagonism in the basal ganglia and hypothalamus precipitates neuroleptic malignant syndrome (NMS).
  2. Step 2: The diagnostic tetrad of NMS comprises severe generalized lead-pipe rigidity, hyperthermia, altered mental status, and autonomic instability with massive creatine kinase elevation following antipsychotic exposure.
Answer
Neuroleptic malignant syndrome.
Why not the others: Serotonin syndrome features hyperreflexia and spontaneous neuromuscular clonus rather than lead-pipe rigidity. Malignant hyperthermia is triggered by volatile inhaled anesthetics (such as halothane) or succinylcholine in genetically susceptible individuals with ryanodine receptor mutations. Catatonia presents with waxy flexibility without hyperthermia or massive rhabdomyolysis.

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