[Diazepam-responsive malignant catatonia in a patient with an initial clinical diagnosis of neuroleptic malignant syndrome: a case report].

We report a case of malignant catatonia initially diagnosed as neuroleptic malignant syndrome (NMS) that responded successfully to diazepam administration. A 29-year-old man with mental retardation was admitted to our hospital because of high fever, muscle pain, and consciousness disturbance. Fifteen days before admission, he had developed muscle pain and weakness in his legs. He presented with fever, tachycardia, tachypnea, elevated blood pressure, excessive sweating, and neurological findings of lethargy and severe muscle rigidity in the neck and extremities. Laboratory findings included elevated serum creatine phosphokinase (CPK) level. His clinical features and the laboratory test results fulfilled the diagnostic criteria for NMS. He was treated for NMS with dantrolene sodium and bromocriptine mesylate for 2 weeks; however, there was no improvement. Therefore, treatment was changed to diazepam administration because of suspected malignant catatonia. One week after initiation of diazepam administration, his symptoms gradually improved, and the serum CPK level normalized. The diagnosis of malignant catatonia was confirmed because treatment with diazepam was dramatically effective, whereas the initial treatment for NMS was not beneficial. The clinical presentation of malignant catatonia is similar to that of NMS. Indeed, some authors have described NMS as a variant of malignant catatonia. If treatment is refractory in cases of NMS, malignant catatonia may be suspected, and changing treatment to diazepam administration may be useful.