ICI-mediated endocrinopathies are among the most frequent irAEs, which occur in 4% to 30% of patients,[13] while ICI-related autoimmune diabetes mellitus (DM) is extremely rare, with an observed incidence ranging from 0.2% in randomized clinical trials[14] to 0.9% in real-world settings.[15] Herein, we report an especially rare case of an advanced small cell lung cancer (SCLC) patient who simultaneously developed CIP and DM after the eighth cycle treatment with PD-L1 inhibitor durvalumab. The gene discussed is CD274; the disease is diabetes mellitus.