The cause of Paget’s disease is not known, but doctors have identified a number of risk factors that make someone more likely to develop the disease. These include: Genetics. Paget’s disease tends to run in families. In as many as 25 to 40 percent of cases, another relative will also have the disease; Age – Paget’s disease occurs only rarely in people under 40 years of age. It is more common as people age; Environmental factors – Some studies suggest that certain environmental exposures may play a role in the development of Paget’s disease.