Effect of intravenous pamidronate on bone markers and local bone mineral density in fibrous dysplasia

Bisphosphonates have proven to be effective in patients with fibrous dysplasia of the bone (FD) as shown by their effect on bone pain, markers of bone turnover, or radiological changes. The aim of this study was to evaluate the usefulness of measuring bone mineral density (BMD) of affected bones to assess the efficacy of bisphosphonate treatment. Seven patients (mean age 26 years) received courses of 180 mg intravenous infusion of pamidronate every 6 months (60 mg/day during 3 days). Clinical symptoms, serum alkaline phosphatase, and urinary C-terminal cross-linking telopeptide of type I collagen were assessed every 3 months. BMD of total skeleton and X-rays of FD areas (FDa) were performed at baseline and at 12 months. BMD of FDa was compared with the contralateral side (CL) using the region of interest program on the total skeleton scan. BMD of total skeleton was normal at baseline. Average BMD of FDa was −11.4% compared with CL, a significantly greater difference than that observed between the left and right sides in healthy controls, −0.7% (P< 0.02). At 12 months bone pain diminished in all patients. Bone turnover markers decreased. Mean total skeleton BMD increased 3.3% (P< 0.02). Subregions of the total skeleton scan presenting FD lesions augmented: arms +9.6% (P< 0.02), legs +4.2%, and pelvis +3.5% (P< 0.05). The increase in mean BMD of FDa was +6.8% compared with +2.6% in CL. No changes were observed on the X-ray. These results indicate that simultaneous determination of markers of bone turnover and BMD of FDa is useful in short-term follow-up to determine the efficacy of intravenous pamidronate.