Type 1 Diabetes Mellitus and Pernicious Anemia in an Elderly Japanese Patient: A Case Report and Literature Review.

We herein report the case of a 66-year-old Japanese man with acute-onset type 1 diabetes mellitus (T1D) accompanied by pernicious anemia. After 2 weeks of polyuria, the patient developed insulin-deficient hyperglycemia with diabetic ketoacidosis in the absence of verifiable islet-related autoantibodies and began insulin therapy in 2001. Eight years later, he developed gastric autoantibody-positive pernicious anemia and began methylcobalamin treatment. Previous studies have reported cases of slowly progressive autoimmune T1D concomitant with pernicious anemia. The present case suggests that potential associations with organ-specific autoimmune disorders should be considered during the long-term follow-up of T1D patients, even though verifiable islet-related autoantibodies are undetectable.