Prompt clinical and biochemical response to denosumab in a young adult patient with craniofacial fibrous dysplasia.

Background: We report on the clinical and biochemical outcomes in a 20-year-old male suffering from active craniofacial monostotic fibrous dysplasia (MFD) of the left mandible treated with the RANK-L inhibitor, denosumab, following unsatisfactory responses to prior long-term bisphosphonates therapy.

Results: The patient had been treated over 9 years with pamidronate (cumulative dose of 810 mg) with incomplete control of pain. Following initiation of denosumab 60 mg subcutaneously, bone pain and bone turnover markers (osteocalcin, total and bone alkaline phosphatase and carboxy-terminal cross-linking telopeptide of type I collagen) were monitored over a 27 months period. Few hours after the first administration, the patient demonstrated a complete pain disappearance and after 4 weeks bone turnover markers fell within the normal range. Three months after denosumab initiation the patient reported a pain reactivation that required a second administration, which again led to the pain disappearance. Subsequently, denosumab was administered according to the pain reappearance and the injection was always followed by complete pain relief. However, a gradual shortening of the pain-free interval between administrations was observed, ranging from 90 to 75 days. All bone turnover markers stayed in the lower half of the normal range, even at the moment of pain reappearance, suggesting that the effect of denosumab on pain depends on mechanisms other than bone resorption suppression. No side effects were reported by the patient during the follow-up.

Conclusion: Denosumab appears to be effective in reducing bone turnover and bone pain in adult patients with active MFD.