Type 1 diabetes developed in a type 2 diabetic patient with severe insulin resistance

We report a 38-year-old female with severe insulin resistance who developed type 1 diabetes after being diagnosed with type 2 diabetes. At the initial examination, BMI was 31.8 kg/m2 and HbA1c 10.8%. Her insulin secretion was sufficient (urinary CPR 80 μg/day) and the GAD antibody was negative. Following treatment with insulin and glimepiride, HbA1c decreased to 6.3%, though diabetic control deteriorated after 1 year (HbA1c, 11.0%) and her body weight was reduced in a short period, from 78 to 67 kg. Re-examination revealed that the GAD antibody was high (1870 U/mL, normal <1.5) and the anti-islet cell antibody positive, and insulin secretion decreased (urinary CPR 18 μg/day). Further, a hyperinsulinemic-euglycemic cramp study using an artificial pancreas showed that the patient had severe insulin resistance [glucose infusion rate 1.8 mg/(min kg); normal, 7.4 ± 2.4 (mean ± S.D.)]. An HLA-analysis showed that she was a homozygote of haplotype DRB1*0901-DQB1*0303. In spite of strict insulin therapy, glucose control was not improved. Pioglitazone could not be used because of side effects, however, metformin was effective for glucose control. The accumulation of case reports of patients with type 1 diabetes and insulin resistance is important for studying the relationship between the onset of the disease and insulin resistance, and for developing an effective treatment strategy.