Neuroleptic malignant syndrome (NMS) is a life-threatening condition associated with the use of neuroleptic drugs and is characterized by a clinical syndrome of mental status change, muscle rigidity, fever, and autonomic instability. The incidence of NMS seems to has been decreasing, possibly due to increased awareness, changes in drug prescribing practices, the use of lower doses of dopamine blocking agents and atypical antipsychotics. The risk factors most consistently identified with precipitating NMS are prominent psychomotor agitation and incrementally higher doses of one or more parenterally administered neuroleptics. The use of atypical antipsychotics may be associated with: a decreased risk, decreased mortality, and atypical features of NMS.

To alert clinicians for atypical presentations of NM.

To report and discuss, based on online pubmed database, a case of a NMS with no muscle rigidity, in spite of an extremely elevated CK level, due to quetiapine.

Atypical cases of NMS without muscle rigidity and/or hyperthermia have been reported in database. With the widespread use of atypical antipsychotics, atypical presentations of NMS should be more frequent. While not yet proven, it has been hypothesized that such atypical cases are a prodrome of the disease and represent impending NMS with typical presentation.

Clinicians must be aware for this atypical presentation of the NSM since adherence to strict diagnostic criteria may lead to alternate and/or delayed diagnosis, with eventually poor outcomes. For this reason, a strong clinical suspicion based on clinical history is crucial for early diagnosis and treatment.