Type 1 diabetes is considered 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 process, but evidence suggests that both a genetic predisposition and environmental factors, such as a viral infection, are involved.
Researchers have found at least 18 genetic locations, labeled IDDM1 - IDDM18, which are related to type 1 diabetes. The IDDM1 region contains the HLA genes that encode proteins called major histocompatibility complex. The genes in this region affect the immune response. Other chromosomes and genes continue to be identified.
Most people who develop type 1 diabetes, however, do not have a family history of the disease. The odds of inheriting the disease 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 twin 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 40 years, a major increase in the incidence of type 1 diabetes has been reported in certain European countries, and the incidence has tripled in the U.S.
Some research suggests that viral infections may trigger the disease in genetically susceptible individuals.
Among the viruses under scrutiny are enteric viruses, which attack the intestinal tract. Coxsackie viruses are a family of enteric viruses of particular interest. Epidemics of Coxsackie virus, as well as mumps and congenital rubella, have been associated with type 1 diabetes.
Review Date: 05/05/2011
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.