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/d
l detected in a blood test. Laboratory studies showed a urinary CPR concentration of 21.9
μg/day and serum CPR of 0.2 ng/m
l before and 0.4 ng/m
l 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/m
l) , 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.
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