[Fulminant blood sugar increase - a rare but life-threatening course].

A 71-year-old patient with known metastatic melanoma undergoing treatment with the immune checkpoint inhibitors Ipilimumab/Nivolumab presented with a rapid deterioration in general condition over the past 24 hours. Approximately three weeks after starting ICI-the-rapy, thyroiditis was diagnosed, which progressed to a substitution-requiring hypothyroidism. Currently, laboratory tests revealed severe keto-acidosis with acute blood sugar derangement (51 mmol/l) despite only a mildly elevated HbA1c (6.3 %). We hereby diagnosed fulminant ICI- associated type 1 diabetes mellitus. Symptoms improved under insulin therapy.