Type 1 diabetes usually is diagnosed in children and teenagers. For this reason, it used to be called juvenile diabetes. It also is often diagnosed in people in their 20s. Diagnosis after age 30 is much less common.
In the United States, 1 out of every 400 to 600 children and teenagers has type 1 diabetes. The International Diabetes Federation estimates that around the world, close to 430,000 children have this condition. Both genes and environment seem to be involved in causing this disease. Environment includes what you are exposed to and what happens to you in your life.
No specific "diabetes gene" has been found. But many genes have been linked to type 1 diabetes. The best-studied is a cluster of genes known as the HLA complex. Genes contain the blueprints for making proteins. Proteins from the HLA group affect how the immune system responds to foreign substances.
Certain combinations of HLA gene types are more common in people with type 1 diabetes. We still don't know why this is the case. And HLA gene types are clearly not the whole story. Many people who have HLA patterns associated with type 1 diabetes never develop the disease.
The patterns of this disease in families show that more than genes must be involved. Most people with type 1 diabetes don't have a first-degree relative with the disease. Also, when one identical twin has type 1 diabetes, the other twin, with identical genes, has less than a 50% chance of developing the disease.
One trigger for type 1 diabetes may be a virus. Perhaps it could be a common childhood virus such as a cold, flu or diarrhea. One or more particular viruses may be able to activate the immune system. But instead of just fighting the infection, the body attacks the pancreas with the same antibodies or immune cells. Most people with type 1 diabetes have antibodies that could be blamed for this type of autoimmune response.
The most common antibodies formed in people who go on to develop type 1 diabetes are islet cell antibodies. They damage cells in the pancreas that make insulin. Some children with diabetes make a second type of antibodies, which can damage cells in the thyroid gland. Children who are newly diagnosed with diabetes should have a blood test to check for thyroid problems, too.