SAN FRANCISCO — The rise in the diagnosis of type 2 diabetes among children is calling attention to certain differences in disease characteristics between children and adults, Dr. Francine Ratner Kaufman, reported at the Third World Congress on Insulin Resistance Syndrome.
In fact, some children seem to have a form of diabetes that's a hybrid between type 1 and type 2, said Dr. Kaufman of the University of Southern California, Los Angeles. Workers in the field have used a variety of designations for this, including “hybrid diabetes,” “double diabetes,” “type 1.5,” and “type 3.”
The typical child with type 1 diabetes will have a positive antibody test and low fasting C-peptide values. The situation is reversed in the typical child with type 2 diabetes-negative antibodies and high fasting C-peptide. But some children have a positive antibody test along with high fasting C-peptide levels. It's those children who have the hybrid form.
“A fair number of these children who come looking as if they have type 2 diabetes also have evidence of islet-cell autoimmunity,” Dr. Kaufman said. “Whether that represents that they have type 1 or type 2 diabetes or that this evidence of antibody is a different phenomenon than it is in the adult population, we don't know.”
Before insulin pumps and refined glucose control, children with type 1 diabetes were typically underweight. Better control means that more of these children are of normal weight, and about 20% may even be obese. That means that obesity alone cannot be used to distinguish type 1 from type 2 disease, even though at least 85% of children with type 2 diabetes are overweight or obese.
Type 2 diabetes seems to take a somewhat different course in children than in adults. In adults the disease is often indolent, preceded by a long asymptomatic period. Screening reveals many adults who have undiagnosed type 2 diabetes. In contrast, at least five studies of overweight children, who would be expected to be at high risk of type 2 diabetes, have found very low rates—6% or less—of undiagnosed type 2 diabetes. This may indicate that children progress more rapidly than do adults through progressive B-cell failure to type 2 diabetes.
A recent study found few parameters that can help distinguish children who have impaired glucose tolerance and will go on to develop type 2 diabetes from those who will revert to normal glucose tolerance (Diabetes Care 2005;28:902–9). The two groups were similar in fasting and postprandial glucose, insulin, and C-peptide levels, for example. The best predictor turned out to be rapid increases in weight and body mass index.
Similarities between the two types, along with the presence of a hybrid form, argue for the “accelerator hypothesis,” which views type 1 and type 2 diabetes as the same disorder of insulin resistance, set against different genetic backgrounds, Dr. Kaufman said.