Untreated Paget disease of bone studied by scintigraphy.

We determined that the concentration of radioactivity in a lesion of Paget disease correlates with the grade of radiological deformation and the frequency of pain; the total skeletal uptake correlates with the severity of the biochemical abnormalities. We suggest that the major determinant of uptake in untreated lesions is abnormal metabolic activity, and in lesions in remission it is structural deformation of mineralized tissue. It is likely that the metabolic activity, and possibly also the rate of progression of the individual lesions, will differ in the individual patient, and that metabolic activity determines the amount of deformation and the chance of pain. Lesions not visible on the radiograph usually show only low uptake of Tc-99m-Sn-EHDP; the majority of these lesions are asymptomatic and reflect low activity of the disease. Radiological differentiation between sclerotic and osteolytic lesions does not reflect differences in either scintigraphic uptake, metabolic activity, or pain.