An Unusual Cause of Persistent Tachycardia: Atypical Neuroleptic Malignant Syndrome.

Neuroleptic malignant syndrome (NMS) is a rare, life-threatening emergency caused more commonly by typical antipsychotics. However, unusual presentations of NMS are intermittently reported with the use of atypical antipsychotics. We present the case of a 42-year-old gentleman with schizoaffective and bipolar disorder who was admitted for change in mentation and lithium toxicity. His mentation did not improve despite being dialyzed and the resolution of lithium level to baseline. He developed persistent tachycardia and hyperthermia, initially attributed to  infection. But despite appropriate antibiotic therapy, his clinical symptoms did not improve. An extensive workup for his neurological symptoms, including lumbar puncture, 5-hydroxy indole acetic acid urine test, and brain magnetic resonance imaging, was inconclusive of any underlying etiology. Given the suspicion of atypical NMS, bromocriptine 2.5 mg three times daily was initiated. This led to the gradual resolution of his symptoms and a return to his baseline mental status. Diagnosing atypical NMS can be challenging and must be differentiated from similar disorders. Lithium toxicity can predispose patients to develop NMS.