Type-1 diabetes and celiac disease, also known as gluten intolerance, share at least some genetic roots, researchers reported on Wednesday.
The findings may lead to new treatments for such autoimmune diseases, which are caused when the body's immune system mistakenly destroys healthy tissue.
The results of the study, published in the New England Journal of Medicine, also point to some of the same environmental triggers causing both conditions.
"These findings suggest common mechanisms causing both celiac and type-1 diabetes. We did not expect to see this very high degree of shared genetic risk factors," David van Heel of St. Barts Hospital and The London School of Medicine and Dentistry said in a statement.
The international team studied 9,339 healthy people, 8,064 people with type-1 diabetes and 2,560 people with celiac disease.
They found four celiac disease genetic mutations that also appeared often in people with type-1 diabetes and two diabetes mutations that also appeared to raise the risk of celiac disease.
Type-1 diabetes, also known as juvenile diabetes, is caused by the destruction of beta cells of the pancreas that produce the insulin necessary to regulate blood sugar levels. It is different from the far more common type-2 diabetes, strongly linked with poor diet and a lack of exercise.
Celiac disease, also an autoimmune disorder, attacks the small intestine and makes patients intolerant of gluten, a protein found in wheat, barley and rye. Symptoms include bloating, abdominal pain, nausea, skin problems, depression, joint or bone pain and nerve problems.
"The next step is to understand how these susceptibility genes affect the immune system, and to keep exploring environmental factors that might alter the risk of type-1 diabetes, which results from an incredibly complex interaction between nature and nurture," said John Todd of Britain's University of Cambridge.
The findings, Dr. Robert Plenge of Brigham and Women's Hospital in Boston wrote in a commentary in the journal, "have implications beyond the shared genetic causes of type-1 diabetes and celiac disease."
Lupus and rheumatoid arthritis, two other autoimmune diseases, have also been linked in studies, Plenge wrote. He said the findings are likely to lead to new treatments for the conditions.
According to the World Health Organization, at least 171 million people worldwide suffer from diabetes, with about 5 to 10 percent of them having type-1.
Celiac disease is estimated to affect about 1 percent of people of European descent.
Reuters