Diabetes: Type 1
DescriptionAn in-depth report on the causes, diagnosis, and treatment of type 1 diabetes.
Alternative NamesInsulin-dependent Diabetes Mellitus; Juvenile Diabetes
Type 1 diabetes is usually a progressive autoimmune disease, in which the beta cells that produce insulin are slowly destroyed by the body's own immune system. It is unknown what first starts this cascade of immune events, but evidence suggests that both a genetic predisposition and environmental factors, such as a viral infection, are involved.
Certain factors are thought to be important in this process:
Progression from the first stage, known as insulitis, to full-blown diabetes can take seven years or longer. Unfortunately, by the time a person is aware that something is wrong and goes to the doctor with symptoms of type 1 diabetes, about 80% to 90% of the beta cells have been destroyed.
It should be noted that more than half of those with insulitis does not develop diabetes. Researchers are greatly interested in discovering any factors that prevent the disease.
Researchers have found at least 18 genetic locations that are related to type 1 diabetes. They appear to involve abnormal interactions among normal genes, mostly those known as I and II major histocompatibility genes, which affect the immune response.
The odds of inheriting the disease, however, are only 10% if a first-degree relative has diabetes, and even in identical twins, one twin has only a 33% chance of having type 1 diabetes if the other has it. Children are more likely to inherit the disease from a father with type 1 diabetes than from a mother with the disorder.
Genetic factors cannot fully explain the development of diabetes. Over the past 30 years, a major increase in the incidence of type 1 diabetes has been reported in certain European countries, and the incidence has nearly tripled in the Northeastern U.S. If genetic factors were the only cause of type 1 diabetes, such an increase in cases would take at least 400 years.
Some researchers believe one or more viral infections may trigger the disease in genetically susceptible individuals. Researchers suggest the following scenario:
Among the viruses under scrutiny are enteric viruses, which attack the intestinal tract. Coxsackieviruses are an enteric virus of particular interest. (One study has suggested that respiratory infection in a child's first year, and not later, may be protective against diabetes, perhaps by priming the immune response so that it is better able to respond later on to other organisms.)