At least seven genes may account for the development of a type of arthritis which affects up to one million people in the UK, scientists have discovered.
The team of international researchers hope the discovery will bring genetic screening to identify those at risk of developing Paget's disease a step closer.
The condition impacts the way bone develops and renews itself and can lead to enlarged and malformed bones.
It affects more people in the UK than anywhere else in the world.
Scientists, led by the University of Edinburgh, believe the genes are involved in regulating the rate at which bone is renewed and repaired, providing an explanation of why the disease occurs.
Professor Stuart Ralston, Arthritis Research UK professor of rheumatology, headed the the study and said the results could be a "major advance" in dealing with the bone disease.
He said: "We have now identified seven genes that predispose people to Paget's. The effect of these is large, and together they considerably increase the risk of developing the condition.
"Our work shows that these genes together very strongly predict the development of Paget's disease.
"Their effects are so powerful that they could be of real value in screening for risk of the disease. This is important since we know that if treatment is left too late, then irreversible damage to the bones can occur.
"If we were able to intervene at an early stage with preventative therapy, guided by genetic profiling, this would be a major advance."
The study, published in the journal Nature Genetics, confirms how genes play a crucial role in the development of Paget's disease, explaining why many patients have a family history of the condition.
Researchers funded by Arthritis Research UK and the Paget's Association studied 2,215 patients with the disease to find the genes that could cause the condition.
The team, including scientists from the UK, Australia, Spain, Italy, Holland, and Belgium, found four genes that were faulty more frequently in patients with the bone disease than in healthy people.
Previously, they used a similar approach to identify three genes that caused the condition.
Professor Ralston is now setting up a clinical trial to identify people at risk of Paget's and to offer them preventative treatment.