New-onset diabetes in an obese adolescent: diagnostic dilemmas

A 14-year-old, obese, African American boy presented to his pediatrician with polyuria, polydipsia, and a significant unintentional weight loss. He was dehydrated, with high levels of blood sugar and urinary ketones. He had no history of previous illnesses and was not taking any medications. He had a family history of type 2 diabetes mellitus.

Physical examination included assessing stigmata of insulin resistance, and measuring blood pressure, pulse, and BMI. Blood samples were obtained for measurement of venous blood pH, bicarbonate, serum glucose, electrolytes, HbA(1C), aminotransferases and lipids. Urine was sampled for measurement of ketones. Subsequently, measurements of fasting C-peptide and immunoassays for insulin autoantibodies (IAA), islet-cell autoantibodies (ICA-512) and glutamic acid decarboxylase autoantibodies (GAD-65) were performed.

New-onset diabetes mellitus with diabetic ketoacidosis, initially diagnosed as type 2 diabetes mellitus, but later determined as type 1 diabetes mellitus.

After treatment of diabetic ketoacidosis with hydration and insulin infusion, the patient was discharged on subcutaneous insulin. He was diagnosed with type 2 diabetes mellitus and was transferred to oral insulin-sensitizing agents. He re-presented 18 months later with an insulin requirement during an asthma exacerbation treated with steroids. Due to the worsening of his diabetic symptoms, the patient was tested for islet autoantibodies and was found to be positive for GAD-65 and IAA, that is, diagnostic of type 1 diabetes mellitus. He has continued to require subcutaneous insulin.