Diagnostic uncertainty in a case of neuroleptic malignant syndrome.

Neuroleptic malignant syndrome (NMS) is a potentially life-threatening condition that has been associated with antipsychotic use. Most diagnostic criteria include fever and muscle rigidity, although NMS may present without either. Diagnostic uncertainty in such cases may result in delays in diagnosis and management, leading to adverse consequences for these patients. The differential diagnosis of NMS is broad and includes a number of neurological, medical and psychiatric conditions as well as substance and medication-induced disorders. A case is described that illustrates an atypical presentation of NMS and demonstrates some of the challenges in its diagnosis. Limitations of current NMS criteria are also examined, and suggestions for future criteria are presented.