Hsiao, Edward C

Background: Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare, disabling, genetic disorder characterized by progressive heterotopic ossification (HO). FOP care pathways are complex, and there are many underrepresented patients globally. Objectives: This scoping review aimed to identify global FOP case reports and investigate real-world management practices. Evidence sources, eligibility criteria, and charting methods: International/local databases and congress proceedings were searched. Publications reporting patient-level data for ⩾1 patient with an FOP primary diagnosis, published January 2000–January 2024, were eligible. Publication details, patient demographics, disease presentation, and care pathway were extracted. Data were charted through categorization of themes and frequency analyses. Results: Of 6064 publications screened, 369 were eligible, reporting on 541 patients with FOP. Most publications (82.4% (304/369)) reported an individual case; the remaining reported 2–25 cases. Cases were from 57 countries, most commonly in the Asia/Pacific region (47.0% (254/541)). Most patients had reportedly seen a single specialist (64.8% (59/91)), and care from multidisciplinary teams was reported for only 5.5% (5/91). HO (84.7% (458/541)) and great toe malformations (66.7% (361/541)) were the most commonly reported signs, though mobility limitations (46.2% (96/208)) and growths/lesions (38.5% (80/208)) were most common before diagnosis. The predominant drug classes reported for FOP treatment were corticosteroids (52.6% (102/194)) and nonsteroidal anti-inflammatory drugs (39.7% (77/194)). Surgeries were reported in 35.1% (190/541) of patients. Where specified, the most common surgery types were malformation correction/bone resection (43.6% (78/179)) and biopsies (34.1% (61/179)). Conclusion: This scoping review synthesized valuable real-world insights from case reports of FOP, potentially supporting outreach initiatives in underserved regions and facilitating shared learnings on diagnosis and treatment. Although the inherent selection bias of case studies toward atypical cases limits definitive conclusions, some global trends in the clinical management practices were revealed.

Abstract Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic condition characterized by congenital malformations of the great toes and progressive heterotopic ossification (HO) in specific anatomic patterns. Present management summarized here is focused on early diagnosis, assiduous avoidance of injury and iatrogenic harm, symptomatic amelioration of painful flare-ups, and optimization of residual function. Twenty-one members of the International Clinical Council on FOP (ICC) and seven consultants from 15 countries, chosen for their clinical expertise in FOP, developed this summary statement. Further advances in therapeutics will be based on rigorous clinical trials to assess novel and emerging treatment and prevention strategies. A detailed and updated exploration of the topics outlined in this brief perspective can be found in “The Medical Management of Fibrodysplasia Ossificans Progressiva: Current Treatment Considerations” which can be found on the International Clinical Council on FOP (ICC) website (www.iccfop.org).

ABSTRACT Bone morphogenetic protein (BMP) signaling is critical in skeletal development. Overactivation can trigger heterotopic ossification (HO) as in fibrodysplasia ossificans progressiva (FOP), a rare, progressive disease of massive HO formation. A small subset of FOP patients harboring the causative ACVR1R206H mutation show strikingly mild or delayed-onset HO, suggesting that genetic variants in the BMP pathway could act as disease modifiers. Whole-exome sequencing of one such patient identified BMPR1AR443C and ACVR2AV173I as candidate modifiers. Molecular modeling predicted significant structural perturbations. Neither variant decreased BMP signaling in ACVR1R206H HEK 293T cells at baseline or after stimulation with BMP4 or activin A (AA), ligands that activate ACVR1R206H signaling. Overexpression of BMPR1AR443C in a Tg(ACVR1-R206Ha) embryonic zebrafish model, in which overactive BMP signaling yields ventralized embryos, did not alter ventralization severity, while ACVR2AV173I exacerbated ventralization. Co-expression of both variants did not affect dorsoventral patterning. In contrast, BMPR1A knockdown in ACVR1R206H HEK cells decreased ligand-stimulated BMP signaling but did not affect dorsoventral patterning in Tg(ACVR1-R206Ha) zebrafish. ACVR2A knockdown decreased only AA-stimulated signaling in ACVR1R206H HEK cells and had no effect in Tg(ACVR1-R206Ha) zebrafish. Co-knockdown in ACVR1R206H HEK cells decreased basal and ligand-stimulated signaling, and co-knockdown/knockout (bmpr1aa/ab; acvr2aa/ab) decreased Tg(ACVR1-R206Ha) zebrafish ventralization phenotypes. Our functional studies showed that knockdown of wild-type BMPR1A and ACVR2A could attenuate ACVR1R206H signaling, particularly in response to AA, and that ACVR2AV173I unexpectedly increased ACVR1R206H-mediated signaling in zebrafish. These studies describe a useful strategy and platform for functionally interrogating potential genes and genetic variants that may impact the BMP signaling pathway. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Clinical trials for orphan diseases are critical for developing effective therapies. One such condition, fibrodysplasia ossificans progressiva (FOP; MIM#135100), is characterized by progressive heterotopic ossification (HO) that leads to severe disability. Individuals with FOP are extremely sensitive to even minor traumatic events. There has been substantial recent interest in clinical trials for novel and urgently‐needed treatments for FOP. The International Clinical Council on FOP (ICC) was established in 2016 to provide consolidated and coordinated advice on the best practices for clinical care and clinical research for individuals who suffer from FOP. The Clinical Trials Committee of the ICC developed a focused list of key considerations that encompass the specific and unique needs of the FOP community – considerations that are endorsed by the entire ICC. These considerations complement established protocols for developing and executing robust clinical trials by providing a foundation for helping to ensure the safety of subjects with FOP in clinical research trials.