Case of autoimmune polyendocrine syndrome type 3 complicated with anti‐N‐methyl‐D‐aspartic acid‐receptor encephalitis

Anti‐N‐methyl‐D‐aspartate receptor (NMDA‐R) encephalitis is an autoimmune disorder in which autoantibodies in the limbic system bind to GluN1 subunits of NMDA‐Rs in the brain. We report a rare case of autoimmune polyendocrine syndrome type 3 complicated by anti‐NMDA‐R encephalitis. After hospitalization for type 1 diabetes, the 39‐year‐old patient developed various schizophreniform symptoms and seizures after cold‐like symptoms. These findings are consistent with the diagnosis of anti‐NMDA‐R encephalitis. Immune‐related encephalitis was suspected at the early phase of the disease, and cerebrospinal fluid was positive for anti‐NMDA‐R antibody. Early steroid pulse therapy was initiated during the disease course. The condition improved gradually to full recovery. Early detection and treatment of anti‐NMDA‐R encephalitis should enhance a positive outcome, considering that besides thyroid diseases and type 1 diabetes, various autoimmune diseases are associated with autoimmune polyendocrine syndrome type 3.