著明な高クレアチンキナーゼ（CK）血症と無言症を呈した抗N-メチル-D-アスパラギン酸受容体抗体脳炎（抗NMDAR抗体脳炎）の1例

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

抗N-メチル-D-アスパラギン酸受容体（抗NMDAR）抗体脳炎では痙攣や不随意運動が見られ，免疫療法以外に抗てんかん薬や抗精神病薬を要することがある。本症例は抗精神病薬の使用で，悪性症候群や横紋筋融解をきたし，ショック状態や著明な高クレアチンキナーゼ血症が生じた。リツキシマブ投与を含めた免疫療法を行い不随意運動期を脱したが，約7カ月後に独歩で退院した後も無言症は長期に後遺した。この脳炎に無言症が出現することはあるが，一時的である。本例で遷延したのは蘇生時に生じた小脳梗塞が関与しているかもしれないが，原因は明らかでない。

Abstract

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)