Abstract
A 38-year-old man with a past history of obesity was admitted for glycemic control. He had been treated for type 2 diabetes with an oral hypoglycemic agent (OHA) until the start of insulin therapy. The serum C-peptide level before and 6 minutes after glucagon administration was 0.8 and 1.1 ng/ml, respectively, and impaired. Testing for GAD antibodies and ICA was negative, but testing for IA-2 antibodies was positive, 3.6 U/ml. Slowly progressive type 1 diabetes mellitus (SPT1DM) was diagnosed, and glycemic control improved on insulin therapy. The HLA type was DR4 and DR13. Impaired insulin sensitivity (GIR 4.67 mg/kg/min) by was demonstrated the euglycemic glucose clamp method. After discharge, his glycemic control improved to an HbA1c level of 6% on 0.3 U/kg/day insulin therapy. One year later, his serum postprandial C-peptide level had decreased 0.2 ng/ml.
Recently type 1 diabetes patients have been classified in subgroups, SPT1DM, based on the presence of autoantibodies and slowly decreasing endogenous insulin secretion. Our patient had a typical history of obesity and had been treated with an OHA for type 2 diabetes before insulin therapy. We considered this case difficult to diagnose by routine serological examinations and therefore have reported it.
