精神科的レンズを超えて：精神科的プレゼンテーションを伴う抗N-メチル-D-アスパラギン酸受容体脳炎の診断における困難

Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder that predominantly affects young women and is often associated with ovarian teratomas. We describe a 21-year-old woman with a history of anxiety who initially presented with agitation, abnormal movements, and headaches. Her symptoms were first attributed to psychiatric causes, leading to multiple emergency department visits and eventual psychiatric admission. Despite escalating antipsychotic treatment, her condition rapidly worsened, marked by severe agitation, hypersexuality, and nihilistic delusions. Two weeks into her hospitalization, positive serum anti-NMDAR antibodies and pelvic imaging revealing a right ovarian teratoma prompted a shift in management to immunotherapy and surgical resection. She subsequently experienced significant cognitive recovery. This case highlights how the predominance of psychiatric symptoms in women with anti-NMDAR encephalitis can obscure timely recognition of the underlying neurologic disease. Early consideration of autoimmune encephalitis in young women with abrupt, treatment-resistant psychiatric symptoms is critical to avoid delays in diagnosis and improve outcomes.