Rapid deterioration of a case of anti–N-methyl-D-aspartate receptor encephalitis with an ovarian teratoma, mimicking viral encephalitis

Anti–N-methyl-D-aspartate receptor (NMDAR) encephalitis has recently emerged as an autoimmune encephalitis syndrome. Younger females are more likely to develop this condition which usually presents as a multistage illness with predominant neuropsychiatric manifestations. It is associated with the neuroglial surface antibodies developing against NMDAR. The association of ovarian teratoma has been well recognised in this condition and tumour resection will intensify the recovery of the illness along with immunotherapy. We present a case of 19-year-old female who presented with acute onset of fever, encephalopathy and facial myorhythmia mimicking acute viral encephalitis. Her clinical status deteriorated within a short period. Later, her CSF became positive for NMDAR antibody and a right ovarian teratoma was detected. Her clinical status markedly improved with immunotherapy and excision of the teratoma following a diagnosis of Anti-NMDAR encephalitis. As a potentially treatable neurological condition, clinicians should be aware of this autoimmune encephalitis syndrome causing encephalitis.