Atypical neuroleptic malignant syndrome in an incarcerated patient: a demographic who may be at increased risk

An incarcerated male patient with a psychiatric history of schizoaffective disorder presented to the emergency department with muscle rigidity and mutism after receiving a 150 mg haloperidol decanoate injection. At the peak of his illness, symptoms included muscular rigidity, mutism, excessive drooling, an altered level of consciousness, tachycardia, diaphoresis and tremors. Atypical neuroleptic malignant syndrome (NMS) was diagnosed after discrediting similar illnesses through clinical reasoning, laboratory and imaging studies. He was successfully treated during a 40-day hospitalisation with lorazepam, amantadine, methocarbamol and supportive care. This case represents an atypical presentation of NMS due to the patient's lack of fever development. Nonetheless, he satisfied many other criteria, most notably rapid symptom onset after receiving a first-generation antipsychotic medication. The case also provides an opportunity to discuss the prevalence of psychiatric illness among the US incarcerated population and incarceration as a risk factor for developing NMS.