Hyperosmolar hyperglycemic state secondary to neuroleptic malignant syndrome

Neuroleptic malignant syndrome (NMS) is often considered to be a precipitating factor for diabetic coma, such as a hyperosmolar hyperglycemic state (HHS). The combination of NMS and a systemic illness such as HHS can be difficult to diagnose because NMS may mask the coexisting condition. Although this coexistence is rare, it may be fatal if not detected early. We report a case of HHS in a 47-year-old male patient that developed after the distinguishing features of NMS had subsided. After the diagnosis of HHS, his recovery was a result of intravenous administration of soluble human insulin and fluid supplementation. Physicians caring for patients with diabetes who are also treated with neuroleptic agents should be aware that NMS may precipitate the development of secondary hyperglycemia despite a history of well-controlled blood glucose levels.