DPPX antibody-mediated autoimmune encephalitis：the first case with breast cancer and review of the literature.

Dipeptidyl-peptidase-like protein 6 (DPPX) antibody-mediated encephalitis is a rare type of autoimmune encephalitis (AE), which mainly manifests as diarrhea accompanied by weight loss, cognitive decline, epileptic seizures, and even psychiatric symptoms. Remarkably, it is also reported to be associated with tumors, predominantly B-cell lymphoma. Overall, the AE remains uncharacterized clinically and its long-term prognosis remains elusive. Herein, we report the first case of DPPX antibody-mediated AE secondary to breast cancer. Importantly, it substantially improves after aggressive immunotherapy. Our case highlights DPPX antibody-mediated AE as a paraneoplastic syndrome and discusses the pearls in its diagnosis and management.