We present a case of a 69-year-old Caucasian male with type 2 diabetes suffering from non-small cell lung cancer and undergoing treatment with pembrolizumab, an anti-programmed cell death protein-1 antibody, who presented to our emergency department with complaints of nausea, vomiting, polyuria, and polydipsia. The gene discussed is PDCD1; the disease is type 2 diabetes mellitus.