Abstract
An 80-year-old woman, who had been diagnosed with diabetes mellitus 14 years previously and treated with sulphonylurea, was admitted to the hospital because of elevated blood glucose and loss of weight of 5 Kg in several months. Laboratory data on admission showed that HbA1c was 11.4%, fasting serum C-peptide was 1.0 ng/ml and 1.9ng/ml 2 hours after breakfast, the increment of serum C-peptide 6 min after glucagon iv load of 1 mg was 0.5ng/ml, and mean urinary C-peptide was 21μg/day. ICA was 20-fold positive and GADAb was counted as 956.0U/ml. The patient had previously been admitted to our hospital one year earlier, and atthat time, ICA and GADAb were negative, fasting serum C-peptide was 1.8ng/ml and 3.9ng/ml after breakfast, and mean urinary C-peptide was 64μg/day.
The fact that islet-associated autoantibodies became positive within one year, and endocrine insulin concentrations progressively decreased, in a patient with a 14-year history of type 2 diabetes, may lead us to conclude that the patient could have two genetic susceptibilities, to type 1 and type 2 diabetes, and that type 1 diabetes overlapped type 2 diabetes within a one-year clinical course.
Even in a patient with long-term type 2 diabetes, if progressive loss of endocrine insulin is recognized, immunological markers of type 1 diabetes should be repeatedly checked.
