Limbic encephalitis associated with AMPA receptor and CRMP5 antibodies: A case report and literature review

AIMS: AMPA receptor (AMPAR) and CRMP5 antibodies are relatively uncommon in limbic encephalitis, and patients with both antibodies are rare. We recently treated such a patient, but the patient died after active treatment. To further understand this disease, we conducted a case report and literature review. DISCUSSIONS: To date, five encephalitis patients, including our patient, have been found to be positive for AMPAR and CRMP5 antibodies. The male‐to‐female ratio of the reported cases is 4:1, and the age range is 26 and 62 years old. All five patients presented with various neuropsychiatric symptoms, including insomnia, abnormal behavior, seizures, extrapyramidal symptoms, and autonomic dysfunction. Four patients had tumors (three invasive thymomas and one suspected lymphoma), and three cases died within a short period of time. No tumor was detected in one of the patients during the follow‐up period; however, after active treatment, the outcome was poor, and the patient developed cachexia. One patient had good response to immunotherapy and tumor therapy and successfully returned to work. CONCLUSIONS: The prognosis of encephalitis associated with AMPAR and CRMP5 antibodies is worse than that of the encephalitis associated with AMPAR antibodies alone. The most likely cause is that this encephalitis is more likely to be accompanied by malignant tumors, leading to a poor prognosis. In addition, it may also be due to some synergistic mechanisms between the two antibodies. Further studies aimed at the prognosis of this type of encephalitis are warranted.