[A very elderly case of acute-onset autoimmune type 1 diabetes mellitus].

An 80-year-old man had systemic malaise and pollakiuria, which developed about 40 days before admission. He underwent treatment at a urology department, but his symptoms did not improve. Since dry mouth additionally developed, he visited his family doctor. As his casual blood glucose level was 629 mg/dl and HbA1c was 12.4%, the patient was referred to our department and admitted on the same day. Continuous intravenous infusion of fast-acting insulin and saline were initiated after admission, and dietary therapy at 1,520 kcal/day was initiated on the following day. Anti-GAD antibody and anti-IA-2 antibody were positive, confirming that the disease was acute-onset autoimmune type 1 diabetes mellitus. A sliding scale of fast-acting insulin followed by intensified therapy using insulin glargine and insulin aspart was performed in the early phase, but the treatment was switched to twice-daily biphasic insulin aspart 30 injection because no diabetic complication was present, although the patient was already totally blind and required assistance from his family for self-injection and to improve his quality of life (QOL). Blood glucose control was favorable, and the patient was discharged on April 2.