Autoimmune encephalitis in a woman with lung adenocarcinoma undergoing treatment with an immune checkpoint inhibitor (Pembrolizumab). What was the trigger: The neoplasm or the treatment?

Autoimmune encephalitis is a condition where patients typically present with short-term memory deficits, psychiatric symptoms, and seizures, all with rapid progression. Recently, cases of limbic encephalitis associated with the use of new antibodies for cancer treatment have been reported, such as the monoclonal antibodies (mAb) IgG4 nivolumab and pembrolizumab, which block the binding of PD-1 to PD-L1 and PD-L2 ligands in the tumor microenvironment. We present the first case of limbic encephalitis related to the use of Pembrolizumab in Mexico.