Combined checkpoint inhibitor therapy causing diabetic ketoacidosis in metastatic melanoma

BACKGROUND There has been a significant improvement in survival of advanced malignancies with the advent of checkpoint inhibitors. These newer treatment modalities come with a wide spectrum of unique side effects, termed immune related adverse events (irAE), ranging from mild skin rash to severe colitis. Included in that spectrum is the rare side effect of autoimmune diabetes mellitus. Despite a few case reports illustrating the incidence of autoimmune diabetes associated with immunotherapy, there has not been much mentioned about exacerbation or acceleration of hyperglycemia in non-autoimmune settings leading to de novo diagnosis of type 2 diabetes mellitus. CASE PRESENTATION We report the case of a 42 year old man with metastatic melanoma and no prior history of diabetes mellitus, who presented with diabetic ketoacidosis (DKA) after 3 cycles of combination checkpoint inhibitor therapy using nivolumab and ipilimumab. New onset diabetes mellitus was diagnosed on the basis of elevated hemoglobin A1c, in the absence of prior personal or family history. Autoimmune or type 1 diabetes mellitus was ruled out with normal levels of anti-glutamic acid decarboxylase 65 (GAD65) antibody, zinc transporter 8 (ZnT8) antibody, and islet antigen-2 (IA-2) antibody. CONCLUSIONS This case report highlights the importance of recognizing rare but serious adverse events related to immunotherapy and incorporation of appropriate tools for early identification and management in national cancer treatment guidelines.