Monostotic Paget's disease

right hip pain , incidental finding of right tibia osteolysis

A male patient, 75 years of age came to our hospital complaining of right hip pain. He had a history of an intacapsular fracture of his right hip five years ago, which had been treated with a Thompson hemiarthroplasty. The pain in the hip of the patient was attributed either to infection of the hemiarthroplasty or to protrusion of the head of the prosthesis into the acetabulum. In order to clarify the cause of the patient’s pain and proceed to the appropriate treatment, a number of laboratory and imaging tests were performed. The bone scintigraphy demonstrated only an immediate accumulation of radionuclide in a wedge-shaped pattern in his right tibia. This appearance, which has been likened to a “blade of grass” or “flame”, is typical of Paget’s disease and corresponds to an osteolytic area during the active phase of the disease (fig1). Following the finding of the bone scintigraphy, an X- ray of the tibia was performed, where a V- shaped radiolucent area clearly demarcated from the adjacent bone and typical of the disease was demonstrated (fig 2). Various X-rays were taken in different parts of the body (skull, pelvis, spine, long tubular bones) but no other part of the body showed involvement in the disease which was compatible with the scintigraphy findings as well. It was concluded that the patient suffered from monostotic Paget’s disease, which is a rare pattern of the disease and was incidentally found in this case.

Paget’s disease (osteitis deformans) is common in middle-aged and elderly persons affecting 3% of the population over the age of 40 years. The precise cause of the disease is still unknown, though many suggestions have been made including inflammatory, neoplastic and viral causes. The viral cause especially a paramyxovirus of the measles group has been strongly supported recently. Paget’s disease is a combination of osteoclastic and osteoblastic activity that accounts for marked elevation of the rate of bone turnover, with succeeding waves of bone destruction and bone formation. In many patients the disorder is diagnosed first as an incidental finding on radiographs obtained for unrelated purposes. On occasion the disease is manifested with severe symptoms and signs such as skeletal, neuromuscular and cardiovascular complications. Namely, the most important complications of Paget’s disease are fractures, neurologic deficits, articular problems or neoplasms. Paget’s disease has a predilection for the axial skeleton particularly the pelvis, sacrum, lumbar spine and skull. Abnormalities of the axial skeleton or the proximal part of the femur are present in approximately 75-80% of the cases, while monostotic Paget’s disease is a pattern evident in only 10-35% of cases. In tubular bones osteolysis begins almost invariably in the subchondral regions of the epiphysis and extend subsequently into the metaphysis and diaphysis, but only exceptionally is Paget’s disease apparent in the diaphysis without involvement of the epiphysis. When present, this latter feature typically occurs in the tibia as a V- or wedge-shaped radiolucent area that has been likened to a blade of grass or flame. In conclusion, Paget’s disease can involve any part of the human skeleton and the diagnosis is generally based on radiographic findings. Even when the disease is confined to one bone – monostotic – which is a rare condition and may be more difficult to diagnose, there are characteristic radiologic findings, which are generally observed and allow an accurate diagnosis and differentiation from other conditions.