Neuroleptic Malignant Syndrome with Normal Creatine Phosphokinase Levels: An Atypical Presentation

Neuroleptic malignant syndrome (NMS) was initially notified as an adverse effect of an antipsychotic agent called chlorpromazine, in 1956. In the past, several case reports of NMS have been reported, even if they did not meet the proposed diagnostic criteria for it. The diagnostic criteria for NMS include increased muscle stiffness, increased body temperature, elevated creatine phosphokinase (CPK) levels by at least four times the upper limit of normal (ULN), autonomic dysfunction, and an altered mental status. We present a case of a 25-year gentleman with schizophrenia, who arrived in the Emergency Department, with significant behavioural changes for a month, accompanied by drowsiness and high-grade fever for two weeks. CPK levels done on two occasions were 669 U/L and 710 U/L, respectively. Persistent hyperthermia and autonomic symptoms with further deterioration in mental status, led to a working diagnosis of NMS. The patient, thereafter, received bromocriptine, benzodiazepines and continuous intravenous hydration, but his clinical condition deteriorated and he expired after nine days of hospital stay. Key Words: Neuroleptic malignant syndrome, Creatine phosphokinase, Hyperthermia, Muscle stiffness.