PDCD1 and aseptic meningitis: Taken together, we should bear in mind the possibility of a variety of irAEs, including destructive thyroiditis, aseptic meningitis, and isolated ACTH deficiency, when immune checkpoint inhibitors such as an anti-PD-1 antibody and/or an anti-CTLA-4 antibody are used in subjects with malignant melanoma or other malignant tumors.