An Unusual Case of Type 1 Diabetes -- or Is It Type 2?

Anne L. Peters, MD, CDE


March 07, 2013

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The Case Patient -- Misdiagnosed?

Hi. I am Dr. Anne Peters from the University of Southern California. Today I want to talk about a case that I saw recently so you can understand how I approached it and what happened next.

The patient was a 70-year-old Korean man who came to see me about 2 years ago. He was on a multiple daily insulin regimen with long-acting insulin plus premium rapid-acting insulin. He had been told that he had type 1 diabetes. His blood sugar levels were up and down -- all over the place. He didn't "carb count" or correct; he more or less tested his blood glucose 3 times daily but inconsistently. He had been diagnosed with type 1 diabetes at about age 60, because he was lean, with a body mass index (BMI) of 25 kg/m2. He was started on pills but shortly thereafter switched to insulin.

Along the way he had coronary artery bypass graft surgery, and he still has significant coronary artery disease. When I saw him, my biggest concern was that his blood sugars were still highly variable on insulin. His A1c was 6.8%, and he was very concerned about that number because he was bright and he knew that the A1c was important. From my perspective, however, a man with known cardiovascular disease who was that brittle needed to be temporized. I needed to get his blood sugar under better control.

Even though he was lean, I thought that perhaps he had type 2 diabetes. Asian individuals develop type 2 diabetes at lower BMIs, so I measured simultaneous fasting C-peptide and glucose levels. The glucose was 90 mg/dL and his fasting C-peptide was 1.2 ng/mL. That told me that he probably had type 2 diabetes that had been misdiagnosed as type 1 because he was relatively lean. The first thing that I did was to prescribe metformin. I prefer to use metformin because it is a great drug for treating type 2 diabetes, and I wanted to gradually reduce his blood sugar levels without causing hypoglycemia.