Paget'sdisease is the second most common bone disease after osteoporosis. Characteristics of Paget's disease include increased bone destruction followed by abundant new bone formation. The increased growth of bone results in bone pain, arthritis, deafness and nerve problems due to the entrapment of the nerves by the new bone. The primary cell type that is abnormal in Paget's disease is the osteoclast. Osteoclasts are cells that are responsible for bone removal and the release of calcium from the bone.
Osteoclasts also aid in the healing of fractures and building new bone.
Osteoclasts in Paget's disease are markedly increased in number and size and have an enhanced capacity to remove bone, compared to normal osteoclasts. Electron microscopic studies of osteoclasts from Paget's disease patients have shown that they contain structures that resemble the measles virus or canine distemper virus genes. To try to determine if the measles virus has any role in Paget's disease, researchers introduced measles virus genes into normal osteoclast precursor cells. These changes are very similar to that seen in osteoclast precursors found in patients with Paget's disease. These studies thus suggest that the measles virus infection could play a role in the abnormal osteoclast activity that is seen in patients with Paget's disease.