Neuroleptic malignant syndrome is a life-threatening reaction that may occur as a result of taking certain antipsychotic medications. The exact cause of this syndrome is not known, but it may occur when the medication causes a malfunction in the system that regulates the body's temperature.

The first signs of neuroleptic malignant syndrome include high fever and changes in a person's heart and breathing patterns. People who take antipsychotic medications and develop these symptoms need to be seen immediately by a health professional.