Atypical Neuroleptic Malignant Syndrome Without Hyperthermia: A Case Report.

Neuroleptic malignant syndrome (NMS) is a rare but potentially life-threatening complication associated with antipsychotic use. Although classically characterized by hyperthermia, rigidity, altered mental status, and autonomic instability, atypical presentations lacking key features are increasingly recognized. We present the case of a 21-year-old male admitted for psychosis and behavioral dysregulation who developed elevated creatine kinase (CK), hypertension, and tachycardia following treatment with multiple antipsychotics, including olanzapine and long-acting injectable aripiprazole. Notably, the patient remained afebrile and did not exhibit significant rigidity, complicating the diagnosis. This case highlights the diagnostic challenges of atypical NMS and emphasizes the importance of maintaining clinical suspicion in patients with autonomic instability and elevated CK in the absence of classic features. Early recognition is essential to prevent morbidity and mortality.