[Neuroleptic Intolerance and Residual Mutism in a Young Woman with Anti-N-Methyl-D-Aspartate Receptor (NMDAR) Encephalitis].

We report a case of anti-NMDAR encephalitis and residual mutism in a 23-year-old woman who presented with neuroleptic intolerance. Admission to our department for investigation of her abnormal behavior revealed cerebrospinal fluid (CSF) positivity for anti-NMDAR antibodies, and the patient underwent immunotherapy. However, generalized tonic seizures developed, requiring mechanical ventilation in the intensive care unit. Antipsychotic drugs were also administered for involuntary movements and insomnia. Thereafter, a malignant syndrome of severe hyperCKemia (Max: 191,120 IU/L) and shock developed, requiring resuscitation and three sessions of hemodialysis. Subsequent rituximab therapy led to improvement, except for mutism, which had newly developed during resuscitation. Seven months after initial admission, the patient was discharged with independent gait. However, her mutism still persists. Temporary mutism has been reported to occur in this type of encephalitis, albeit rarely. The fact that remission was not observed in this case may have been due to cerebellar infarction occurring during resuscitation, but the true cause remains unclear. Malignant syndrome or rhabdomyolysis, as seen in this patient, has also sometimes been reported in this form of encephalitis when antipsychotic agents, especially dopamine receptor blockers, have been administered. Therefore, such agents should be administered with caution in patients with anti-NMDAR encephalitis. (Received August 17, 2023; Accepted October 24, 2023; Published March 1, 2024).