A Case of Elderly-Onset Type 1 Diabetes with First-Degree Family History with Negative GAD Antibody and Positive IA-2 Antibody

Abstract

A 50-year-old man, whose second of two daughters was treated for type 1 diabetes, seen for polyuria and weight loss in August 2008 had been found to have HbA_1C of 6.2% in an annual physical cheakup in April 2008. He was hospitalized for markedly elevated HbA_1C of 10.3% and plasma glucose of 463 mg/dl detected in a blood test. Laboratory studies showed a urinary CPR concentration of 21.9 μg/day and serum CPR of 0.2 ng/ml before and 0.4 ng/ml 6 minutes after glucagon administration, indicating decreased insulin secretion. Intensive insulin therapy was initiated. Although GAD antibody was negative, IA-2 antibody was positive (9.1 U/ml) , leading to a diagnosis of type 1 diabetes mellitus. HLA typing was DRB1^*010101 and 090102, type 1 diabetes-susceptibility gene, identical to the typing of his second daughter. This case of elderly-onset of type 1 diabetes is interesting, manifesting negative GAD antibody and positive IA-2 antibody, especially with a family history of type 1 diabetes.