The symptoms of malignant (lethal) catatonia has been reported similar to initial symptoms of anti-NMDAR encephalitis. Subsequently, this autoimmune limbic encephalitis has been noticed in many psychiatrists. We have experienced several cases with malignant catatonia having anti-NMDAR antibody without clinical signs of encephalitis. Thereafter, we have also found anti-NMDAR antibody positive patients of young females with acute florid psychiatric symptoms without clinical signs of encephalitis. The features of these patients mirror-those of "Atypical psychosis" proposed by Mitsuda in Japan, a notion derived from "Cycloid psychosis" conceptualized by German psychiatrist, Leonhard. Both cycloid and atypical psychosis have coinciding features of acute onset, emotional disturbances, psychomotor disturbances, alternations of consciousness, high prevalence in women and oriented premorbid personality. Both malignant catatonia and atypical psychosis have been known to be effectively treated with modified electro convulsion therapy (m-ECT). Our 5 cases with anti-NMDAR antibody, m-ECT treatments were effective. Infectious encephalitis is contra indication of m-ECT, but this autoimmune encephalitis would be careful indication. Schizophrenia is a common, heterogeneous, and complex disorder with unknown etiology. There is established evidence of NMDAR hypofunction as a central component of the functional disconnectivity; this is one of the most accepted models for schizophrenia. Moreover, autoimmune mechanisms have been proposed to be involved, at least in subgroups of schizophrenia patients. Further research of anti-NMDAR antibody and encephalitis would be important clues for the investigation of schizophrenia, catatonia and atypical psychosis.