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.