A Case of Type 1 Diabetes Mellitus With Endogenous Insulin Secretory Depletion Confirmed in Two Weeks.

Type 1 diabetes mellitus (T1DM) is manifested as a decrease in endogenous insulin secretion. With this report, we present a case of T1DM where a rapid decline in insulin secretion was observed in a short span of time. A 56-year-old female patient presented with cold-like symptoms with subsequent dry mouth and malaise to the hospital. Three weeks later, she was diagnosed with diabetic ketoacidosis based on the presence of hyperglycemia, metabolic acidosis, and positive ketone bodies. Her serum connecting peptide (CPR) levels substantially decreased (1.31 to 0.19 ng/mL after two weeks) and she was eventually diagnosed with T1DM. We hypothesized that a subtype T1DM with a longer beta cell loss rate than conventional fulminant type 1 diabetes was involved. This subtype showed characteristics of immune checkpoint inhibitor-associated fulminant type 1 diabetes and is suggested to exist among those diagnosed with conventional acute-onset type 1 diabetes. Finally, we recommend that diabetic ketoacidosis of unknown etiology should be investigated for the concurrent presence of T1DM.