Although fever is considered to be a cardinal feature of neuroleptic malignant syndrome, we report on three patients who were afebrile but had all the other features of the neuroleptic malignant syndrome. This paper highlights the need to suspect neuroleptic malignant syndrome and immediately initiate investigation and appropriate management in any patient who develops rigidity and clouding of consciousness while receiving antipsychotic medication, thus averting potentially lethal sequelae such as death.

The neuroleptic malignant syndrome (NMS) is an uncommon but potentially fatal idiosyncratic reaction characterised by the development of altered consciousness, hyperthermia, autonomic dysfunction, and muscular rigidity on exposure to neuroleptic (and probably other psychotrophic) medications.1 2

According to the DSM IV criteria,3 prominence has been given to signs of increase in temperature (>39^o C) and muscular rigidity. These must be accompanied by two or more of: diaphoresis, dysphagia, tremor, incontinence, altered consciousness, tachycardia, blood pressure changes, leucocytosis and raised creatine kinase concentrations. Some researchers have also advocated that a pyrexia in excess of 38⁰C or 39⁰C is necessary for the diagnosis of NMS.4-5 However, on reviewing the literature since 1965, we found three previous case reports highly suggestive of NMS occurring without fever.6-8 We report three patients who had all the major features of NMS but were afebrile during the entire course of their illness. These cases …