A case of recalcitrant fibrous dysplasia treated with denosumab

Synthetic CT Assessment of Lesions in Children With Rare Musculoskeletal Diseases

Imaging modalities such as computed tomography (CT) are critical for monitoring musculoskeletal abnormalities in children with rare diseases. However, CT exposes patients to radiation, which limits its utility in the clinical setting, particularly during longitudinal evaluation. Synthetic CT is a novel, noncontrast, and rapid MRI method that can provide CT-like images without any radiation exposure and is easily performed in conjunction with traditional MRI, which detects soft-tissue and bone marrow abnormalities. To date, an evaluation of synthetic CT in pediatric patients with rare musculoskeletal diseases has been lacking. In this case series, the capability of synthetic CT to identify musculoskeletal lesions accurately in 2 rare disease patients is revealed. In Case 1, synthetic CT, in agreement with routine CT, identified an intraosseous lesion in the right femoral neck in a 16-year-old female with fibrous dysplasia, whereas standard-of-care MRIs additionally revealed mild surrounding edema-like bone marrow signal. For Case 2, synthetic CT applied to a 12-year-old female with fibrodysplasia ossificans progressiva revealed heterotopic ossification present along the cervical spine that had caused the fusion of multiple vertebrae. Our evaluation of synthetic CT offers important insights into the feasibility and utility of this methodology in children with rare diseases affecting the musculoskeletal system.

Denosumab use in bone fibrous dysplasia refractory to bisphosphonate: A retrospective multicentric study

INTRODUCTION

Increased RANKL expression is observed in the bone tissue of fibrous dysplasia of bone/McCune-Albright syndrome (FD/MAS). In one animal model of FD/MAS, the inhibition of RANKL reduced tumor volume. A beneficial effect of denosumab on pain in patients refractory to bisphosphonates has been reported, but without systematic quantification of pain improvement. This work describes the clinical experience of our group on the efficacy on pain of denosumab treatment, along with safety, in FD/MAS patients refractory to bisphosphonates.

MATERIALS AND METHODS

We have conducted a retrospective multicenter study in 6 academic rheumatology centers in France. We have collected patients and FD/MAS characteristics, duration of prior exposure to bisphosphonates, denosumab treatment modalities (dosage - administration regimen - number of courses); evolution of pain evaluated by Visual Analogic Scale (VAS).

RESULTS

13 patients were included (10 women and 3 men) 45 years on average, 5 MAS, 4 monostotic and 4 polyostotic forms. The average duration post-diagnosis of FD/MAS was 25 years and the mean duration of prior exposure to bisphosphonates was 4.7 years. Pain could be analyzed in 7 patients, showing a significant improvement from a mean VAS of 7.8 to 2.9 (-4.9 points, p = 0.003). In one patient with fronto-orbital FD/MAS, a 30 % decrease in lesional volume, assessed by MRI, was observed within 6 months of treatment, that was sustained over the following 12 months. Treatment regimens were heterogeneous. No hypercalcemia was observed after treatment cessation and the clinical tolerance was good.

DISCUSSION

This study suggests that denosumab reduces pain in patients with DF/MAS refractory to bisphosphonates, and quantifies this improvement for the first time in a multicenter study. In our cohort, no patients who discontinued denosumab developed hypercalcemia and clinical tolerance was overall good. This study also provides encouraging data regarding lesion volume control. Further controlled studies are required to determine the place and modalities of the denosumab treatment of FD/MAS.

CONCLUSION

Denosumab significantly decreased pain in FD/MAS refractory to bisphosphonate. This study paves the way for a randomized clinical trial to validate and standardize the prescription of denosumab in FD/MAS.

Denosumab Use in Adults With Fibrous Dysplasia: Case Reports and Review of the Literature

OBJECTIVE

In fibrous dysplasia (FD) of the bone, a gain-of-function mutation in the G-nucleotide binding protein alpha subunit results in constitutively active cyclic adenosine monophosphate. Downstream effects include formation of disorganized cortex and bone marrow fibrosis. Patients with FD experience bone pain and are at risk of fracture. Bisphosphonates are traditionally used to manage pain with mixed results. We sought to report denosumab use in patients with FD at our institution and summarized the existing literature on denosumab use in FD.

METHODS

We retrospectively identified patients with FD who were treated with denosumab at our institution, describing patient characteristics and outcomes. We reviewed the existing literature on denosumab use in patients with FD.

RESULTS

Patient 1 was diagnosed with FD at the age of 17 years and took bisphosphonates with initial improvement in pain. Pain eventually worsened; therefore, she received 4 doses of denosumab. Patient 2 was diagnosed with FD after a fall and was treated with bisphosphonates, reporting some initial improvement in bone pain. A few years later, the pain recurred, and he received 3 doses of denosumab. Both patients tolerated denosumab well but experienced no improvement in pain. On literature review, although some serious side effects were noted, patients experienced a decline in bone turnover markers, and most reported improvement in bone pain with denosumab.

CONCLUSION

Denosumab is a promising therapy for managing symptoms of FD. Further studies are needed to determine the optimal dose and duration of treatment. Its long-term effect on FD lesions remains unclear.