Onset of fulminant type 1 diabetes mellitus following hypophysitis after discontinuation of combined immunotherapy. A case report

Diabetes is a rare, but potentially life‐threatening, adverse event of immune checkpoint inhibitors that requires prompt recognition and treatment. It usually occurs in the first 3 months of treatment and is typically related to programmed cell death‐1 antibodies, alone or in combined therapy. It has rarely been described developing after immunotherapy cessation. We present a 51‐year‐old man with metastatic melanoma, who developed acute‐onset diabetes 52 days after combined immunotherapy cessation with nivolumab and ipilimumab, and 25.6 months after receiving the first dose. He presented with acute hyperglycemic symptoms, ketosis, complete insulin depletion and negative autoimmunity, fulfilling the criteria of fulminant type 1 diabetes. The patient had previously developed hypophysitis with isolated adrenocorticotropic hormone deficiency during immunotherapy. We describe a case of late‐onset fulminant type 1 diabetes developing after immunotherapy cessation. Patient education and active follow up after immunotherapy discontinuation are crucial to warrant a timely intervention.