The studies show that, as suspected, the immune system is going haywire in lupus. But it also points to some previously unsuspected causes of the once-mysterious disease.

And the findings may not only help scientists find better treatments for the disease - but may help in diagnosing it in the first place, as it is easily confused with other conditions.

Systemic lupus erythematosus, lupus for short, affects at least 1.4 million people in the United States and 50,000 in Britain, advocacy groups say.

It can damage the joints, kidneys, heart, lungs, brain and blood and is marked sometimes by a characteristic butterfly-shaped rash on the face.

Three studies in the journal Nature Genetics and a fourth in the New England Journal of Medicine identify several areas of DNA that carry mutations in people with lupus and their relatives.

"These results suggest biologic pathways that help us understand the condition better and suggest additional genetic and non-genetic triggers," Carl Langefeld, director of the Center for Public Health Genomics at Wake Forest University in North Carolina and one of the study coordinators, said in a statement.

"In addition, they will help delineate the genetic distinctions between rheumatoid arthritis, lupus and other autoimmune diseases, which could lead to earlier, more accurate diagnoses."

One international team of researchers studied the DNA of more than 6,700 women, including people with lupus, their relatives, and unrelated people with no evidence of the disease. Among the four studies, about 10,000 people were tested and 13 different genes were implicated.

"Overall, these papers confirm what investigators have been finding over the past decades," said Dr. Mary Kuntz Crow of the Hospital for Special Surgery in New York.

"They show that many aspects of the immune system are involved in the development of the disease, but they also provide a new level of detail regarding the specific molecular pathways that contribute."

Some of the genes also apparently contribute to blood vessel function and some have unknown roles, the researchers said.

In a commentary in the New England Journal of Medicine, Crow noted that the studies all miss the biggest group of people affected by lupus.

"In the major studies, all of the subjects were of European descent, but lupus is most severe in people with African, Asian and Hispanic backgrounds," Crow said in a statement.

"We need to confirm that these same genes are involved in all of our patient populations and identify any distinct genes that might be involved in those populations at greatest risk for poor outcomes."

Timothy Vyse of Imperial College London said the studies might help researchers develop better treatment.

"Lupus is a complex disease, which is hard to diagnose, and it can cause many different and unpredictable problems for patients. Living with lupus can be really tough," Vyse said in a statement.

"We currently can treat the disease by suppressing the immune system, but we urgently need to understand in much more detail what goes wrong with the immune system so that we can design better treatments."

© Reuters