A modern perspective on the differential diagnosis between encephalitis lethargica or anti-NMDA-receptor encephalitis.

Two cases initially diagnosed as "encephalitis lethargica" are discussed. Both cases satisfied the published diagnostic criteria for encephalitis lethargica, with neuropsychiatric features including complex movement disorder, hypoventilation and altered conscious state. On later investigation N-methyl-D-aspartate receptor antibodies were detected in both cases. With the recent descriptions of tumour related antibodies to neuronal surface antigens in NMDA-receptor encephalitis, we highlight the importance of revisiting a diagnosis which may have prognostic significance. Copyright 2010 Elsevier Ltd. All rights reserved.