Diagnostic Value of Magnetic Resonance Imaging in Fibrodysplasia Ossificans Progressiva

Abstract

Using [18F] Sodium Fuoride (NaF) Positron Emission Tomography (PET) it is not only possible to identify the ossifying potency of a flare‐up, but also to identify an asymptomatic chronic stage of fibrodysplasia ossificans progressiva (FOP). The purpose of this study was to investigate the diagnostic role of a more widely available imaging modality, Magnetic Resonance Imaging (MRI), which is of special interest for studies in pediatric FOP patients. MRI and [18F]NaF PET/CT images at time of inclusion and subsequent follow‐up CT scans of 4 patients were analyzed retrospectively. Presence, location, and intensity of edema identified by MRI were compared with activity on [18F]NaF PET. Occurrence or progression of heterotopic ossification (HO) was examined on the follow‐up CT images. Thirteen different lesions in various muscle groups were identified: five lesions with only edema, five lesions with both edema and increased [18F]NaF uptake, one lesion with only increased [18F]NaF uptake, and two lesions with neither edema nor uptake of [18F]NaF. Mild edema, found in three lesions, was present at asymptomatic sites, which did not show increased [18F] NaF uptake or progression of HO on consecutive CT images. Moderate edema was found in three symptomatic lesions, with increased [18F]NaF on PET and progression of HO on CT. Severe edema was identified in four lesions. Interestingly, two of these lesions did not develop HO during follow‐up; one of these two even gave obvious symptoms of a flare‐up. MRI can identify whether symptoms are the result of an acute flare‐up by the presence of moderate to severe edema. The occurrence of severe edema on MRI was not always related to an ossifying lesion. The additional diagnostic value of MRI requires further investigation, but MRI does not seem to fully replace the diagnostic characteristics of [18F]NaF PET/CT in FOP. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Monitoring and Management of Fibrodysplasia Ossificans Progressiva: Current Perspectives

“…Further research is needed to determine which of these medications can be used in the different stages of FOP activity. 51 If these drugs are found to be effective, future trials might also investigate the removal of existing heterotopic bone.…”

18F-Sodium Fluoride PET as a Diagnostic Modality for Metabolic, Autoimmune, and Osteogenic Bone Disorders: Cellular Mechanisms and Clinical Applications

“…In a different study, increased 18 F-NaF uptake was associated with six progressive but asymptomatic heterotopic lesions that were found in four out of five FOP patients. These results suggest that 18 F-NaF-PET is capable of identifying heterotopic ossification lesions without any preceding flare-ups, demonstrating superiority over MRI [ 101 , 102 ]. In fact, 18 F-NaF is currently the only in vivo biomarker recognized and available for detecting and monitoring the progression of FOP [ 103 ].…”

Diminished muscle integrity in patients with fibrodysplasia ossificans progressiva assessed with at-home electrical impedance myography

“…For some FOP patients, undergoing MRI may also be difficult considering the small-bore size of the magnet in conjunction with physical constraints that patients with FOP often harbor. Moreover, soft tissue edema on MRI and 18 F-NaF-PET/CT activity are respectively associated with localized tissue inflammation and osteogenic activity typically associated with flares, but do not always correlate with the clinical course or predict sites of future HO 15 . To complement clinical and imaging data, recent studies have sought to identify disease and flare-up-associated biomarkers in plasma samples derived from patients with FOP 18 , which if validated in subsequent work, may provide a novel means to classify disease stages of FOP or further the understanding of mechanistic pathways implicated in FOP.…”