Atypical Neuroleptic Malignant Syndrome Presenting as Rhabdomyolysis, Altered Consciousness, and Leukocytosis

Objective: To provide a clinically accurate description of an atypical form of neuroleptic malignant syndrome (NMS) induced by perphenazine, to underline the importance of early diagnosis of this atypical form of NMS, and to stimulate discussion of possible mechanisms of this adverse drug event. Case Summary: A 61-year-old man had received perphenazine for 5 years for treatment of schizophrenia. He presented with progressive muscle rigidity, difficulty walking, and lower back pain. He was found to be disoriented and confused with tardive dyskinesia and muscle weakness. The patient was afebrile and normotensive. Clinical workup and laboratory test results were consistent with a diagnosis of rhabdomyolysis. The patient was treated with rehydration and sodium bicarbonate. Perphenazine therapy was discontinued and the symptoms resolved within 3 days. Discussion: Rhabdomyolysis has been reported in patients receiving psychotropic drugs, but the frequency of the occurrence is not known. The most frequent cause of rhabdomyolysis in psychiatric patients is NMS; however, this patient had only part of the classical picture of NMS. Other cases of atypical presentation are reviewed. Conclusions: Muscle injury in the presence of psychotropic drugs can manifest in many different ways. This suggests a complex mechanism of injury, involving central mechanisms as well as direct injury to the muscle.