Neuroleptic malignant syndrome (NMS) is a rare life-threatening condition associated with the use of antipsychotic medications. This case report describes a male patient in his early 30s who presented with fever, breathlessness, and lower limb weakness, ultimately diagnosed with NMS despite the absence of muscular rigidity. On examination, he was febrile, tachycardic, and tachypneic with an oxygen saturation of 88% and elevated blood pressure. On auscultation diffuse crepitations in both lungs were revealed. Neurological assessment indicated motor strength of 3/5 in both lower limbs, without rigidity, sensory loss, or cerebellar signs. It was noted that he was on irregular atypical antipsychotic medication for the past one year. Laboratory investigations revealed leukocytosis, elevated transaminases, dyselectrolytemia, elevated creatine phosphokinase (CPK), and serum creatinine. NMS was not initially considered due to the lack of muscular rigidity. However, the patient later developed autonomic dysregulation manifestations, such as paralytic ileus. Once organic causes were excluded, NMS was diagnosed. Supportive therapy included 23 cycles of hemodialysis and colonic decompression for pseudo-obstruction. He was treated with intravenous fluids and dopamine receptor agonist medications. NMS usually presents with fever, muscular rigidity, altered mental status, and autonomic instability; yet, the absence of muscular rigidity in this patient is a distinctive and unusual feature.
