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Purpose: We report the first prospective, international, natural history study of the ultra-rare genetic disorder fibrodysplasia ossificans progressiva (FOP). FOP is characterized by painful, recurrent flare-ups, and disabling, cumulative heterotopic ossification (HO) in soft tissues., Methods: Individuals aged ≤65 years with classical FOP (ACVR1 R206H variant) were assessed at baseline and over 36 months., Results: In total, 114 individuals participated; 33 completed the study (mean follow up: 26.8 months). Median age was 15.0 (range: 4-56) years; 54.4% were male. During the study, 82 (71.9%) individuals reported 229 flare-ups (upper back: 17.9%, hip: 14.8%, shoulder: 10.9%). After 84 days, 14 of 52 (26.9%) imaged flare-ups had new HO at the flare-up site (mean new HO volume: 28.8 × 10 3 mm 3 ). Mean baseline low-dose whole-body computed tomography (excluding head) HO volume was 314.4 × 10 3 mm 3 ; lowest at 2 to <8 years (68.8 × 10 3 mm 3 ) and increasing by age (25-65 years: 575.2 × 10 3 mm 3 ). The mean annualized volume of new HO was 23.6 × 10 3 mm 3 /year; highest at 8 to <15 and 15 to <25 years (21.9 × 10 3 and 41.5 × 10 3 mm 3 /year, respectively) and lowest at 25 to 65 years (4.6 × 10 3 mm 3 /year)., Conclusion: Results from individuals receiving standard care for up to 3 years in this natural history study show the debilitating effect and progressive nature of FOP cross-sectionally and longitudinally, with greatest progression during childhood and early adulthood., Competing Interests: Conflict of Interest R.J.P. is a research investigator at Clementia Pharmaceuticals/Ipsen and Regeneron Pharmaceuticals, Inc and is part of the advisory board as President of the International Clinical Council on Fibrodysplasia Ossificans Progressiva. G.B. is part of the advisory boards of Clementia Pharmaceuticals/Ipsen, FOP European Consortium, and International Clinical Council on FOP and is a speaker at Clementia Pharmaceuticals/Ipsen. M.A.B. is part of the advisory boards of AbbVie, Janssen, Pfizer, UCB Pharma, and Novartis; receives grant support from AbbVie; is a research investigator at AbbVie, Clementia Pharmaceuticals/Ipsen, Janssen, Novartis, Pathios Therapeutics Ltd, and Regeneron Pharmaceuticals, Inc; and is a speaker at AbbVie, United States, Janssen, Novartis, Switzerland, Pfizer, United States, Regeneron Pharmaceuticals, Inc, United States, and UCB Pharma, United Kingdom. C.D.C. is a research investigator at Clementia Pharmaceuticals/Ipsen and is a speaker at Novartis. E.C.H. is part (all voluntary) of the Fibrous Dysplasia Foundation Advisory Board, International Fibrodysplasia Ossificans Progressiva Association (IFOPA), United States Registry Medical Advisory Board, and International Clinical Council on FOP Advisory Board; receives clinical research support from Clementia Pharmaceuticals/Ipsen, France, Neurocrine Biosciences Inc, United States, and Regeneron Pharmaceuticals, Inc; and is a research investigator at Clementia Pharmaceuticals/Ipsen. R.K. is a research investigator at Clementia Pharmaceuticals/Ipsen, Kyowa Kirin, and Regeneron Pharmaceuticals, Inc and is part of the IFOPA Fibrodysplasia Ossificans Progressiva Registry Medical Advisory Board and International Clinical Council on Fibrodysplasia Ossificans Progressiva Advisory Board. M.A.M. receives research support from Clementia Pharmaceuticals/Ipsen and Regeneron Pharmaceuticals, Inc; is a non-paid consultant for BioCryst Pharmaceuticals, Inc, United States, Blueprint Medicines, Daiichi Sankyo, Incyte, and Keros Therapeutics; is part (all voluntary) of the IFOPA Registry Medical Advisory Board, Incyte Advisory Board, and International Clinical Council on FOP Advisory Board; and receives non-restricted educational fund from Excel and Catalyst sponsored by Ipsen. K.-H.L.Q.S. is a coordinator of Ipsen FOP-program and multiple osteochondromas-trial. A.W., R.M., and A.S. are employees of Ipsen. F.S.K. is a research investigator at Clementia/Ipsen and Regeneron Pharmaceuticals, Inc, is part of the IFOPA Medical Advisory Board, is a Founder and immediate past President of the International Clinical Council on FOP, and is the Chair of the Publications Committee of the International Clinical Council. In April 2019, Ipsen acquired Clementia Pharmaceuticals., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Fibrodysplasia ossificans progressiva (FOP), an ultra-rare, progressive, and permanently disabling disorder of extraskeletal ossification, is characterized by episodic and painful flare-ups and irreversible heterotopic ossification in muscles, tendons, and ligaments. Prevalence estimates have been hindered by the rarity of FOP and the heterogeneity of disease presentation. This study aimed to provide a baseline prevalence of FOP in the United States, based on contact with one of 3 leading treatment centers for FOP (University of Pennsylvania, Mayo Clinic, or University of California San Francisco), the International Fibrodysplasia Ossificans Progressiva Association (IFOPA) membership list, or the IFOPA FOP Registry through July 22, 2020., Results: Patient records were reviewed, collected, and deduplicated using first and last name initials, sex, state, and year of birth. A Kaplan-Meier survival curve was applied to each individual patient to estimate the probability that he or she was still alive, and a probability-weighted net prevalence estimate was calculated. After deduplication, 373 unique patients were identified in the United States, 294 of whom who were not listed as deceased in any list. The average time since last contact for 284 patients was 1.5 years. Based on the application of the survival probability, it is estimated that 279 of these patients were alive on the prevalence date (22 July 2020). An adjusted prevalence of 0.88 per million US residents was calculated using either an average survival rate estimate of 98.4% or a conservative survival rate estimate of 92.3% (based on the Kaplan-Meier survival curve from a previous study) and the US Census 2020 estimate of 329,992,681 on prevalence day., Conclusions: This study suggests that the prevalence of FOP is higher than the often-cited value of 0.5 per million. Even so, because inclusion in this study was contingent upon treatment by the authors, IFOPA membership with confirmed clinical diagnosis, and the FOP Registry, the prevalence of FOP in the US may be higher than that identified here. Thus, it is imperative that efforts be made to identify and provide expert care for patients with this ultra-rare, significantly debilitating disease., (© 2021. The Author(s).)

Background: Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare genetic disorder characterized by extraskeletal heterotopic ossification. It is well recognized that FOP can lead to a devastating condition of disability. However, the mortality rate of FOP patients in China and risk factors for mortality are still largely unclear., Methods: We conducted a retrospective research on a cohort of 65 cases of FOP patients in China from 2008 to 2018. We reviewed medical records of these FOP patients to retrieve information such as date of birth/death, gender, clinical features, genotypes and biochemical parameters and analyze the correlation of these parameters with the mortality., Results: 92.3% (60/65 cases) patients were classic FOP patients, 3.1% (2/65 cases) were FOP-plus and 4.6% (3/65 cases) were FOP variants. 9 cases of this cohort were dead during the ten-year period, and the overall mortality rate was 13.8%. c.617G > A mutation was confirmed in all non-survivors. In FOP patients≤18 years at diagnosis, non-survivors demonstrated significantly lower blood osteocalcin and alkaline phosphatase levels compared with survivors (P < 0.05), and spearman correlation and logistic regression analysis indicated that serum osteocalcin and alkaline phosphatase levels were negatively correlated with the mortality. Furthermore, the receiver-operating characteristic curve analysis showed serum osteocalcin had the largest area under the curve of 0.855 among four biochemical parameters, and serum osteocalcin < 65.9 ng/ml displayed a good capacity to discriminate the non-survivors from survivors in FOP patients aged 18 years and younger at diagnosis., Conclusions: Our findings showed that the mortality rate of FOP was 13.8% in China. Serum OC level was negatively correlated with the mortality in Chinese FOP patients ≤18 years at diagnosis.

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic skeletal disorder manifesting progressive heterotopic ossification (HO) and congenital malformation of the great toes. Since 2007, we have conducted research on FOP. Here, we review the findings on FOP published to date, including the results of our research. Epidemiological studies in Japan have indicated that FOP has nearly the same prevalence in Japan as in the rest of the world. Basic research on its pathoetiology has progressed rapidly since the identification of the causal gene in 2006. Clinical and radiological findings have been thoroughly researched, including early radiological signs, and diagnostic criteria were established, designating FOP as an intractable disease in Japan. In patients with FOP, the progression of HO is associated with numerous disabilities, often manifesting in vicious cycles that can lead to early mortality. Through cross-sectional and short-term longitudinal studies, we have explored patient education, quality of life, and activities of daily living among Japanese patients. The management of FOP requires education of patients and caregivers, the use of medications to settle inflammation and flare-ups, instructions to ensure proper oral care, and other compensatory approaches that aid in rehabilitation. An avoidance of medical intervention, which may cause HO to progress, is also important. The advent of new drugs to prevent HO could have clinical benefit., (© 2019 Japan Pediatric Society.)

Background: Rare bone diseases account for 5% of all birth defects yet very few have personalised treatments. Developments in genetic diagnosis, molecular techniques and treatment technologies however, are leading to unparalleled therapeutic advance. This review explores the evolving therapeutic landscape of genetic skeletal disorders (GSDs); the key conditions and there key differentials., Methods: A retrospective literature based review was conducted in December 2018 using a systematic search strategy for relevant articles and trials in Pubmed and clinicaltrials.gov respectively. Over 140 articles and 80 trials were generated for review., Results: Over 20 personalised therapies are discussed in addition to several novel disease modifying treatments in over 25 GSDs. Treatments discussed are at different stages from preclinical studies to clinical trials and approved drugs, including; Burosumab for X-linked hypophosphatemia, Palovarotene for Hereditary Multiple Exostoses, Carbamazepine for Metaphyseal Chondrodysplasia (Schmid type), Lithium carbonate and anti-sclerostin therapy for Osteoporosis Pseudoglioma syndrome and novel therapies for Osteopetrosis. We also discuss therapeutic advances in Achondroplasia, Osteogenesis Imperfecta (OI), Hypophosphotasia (HPP), Fibrodysplasia Ossificans Progressiva, and RNA silencing therapies in preclinical studies for OI and HPP., Discussion: It is an exciting time for GSD therapies despite the challenges of drug development in rare diseases. In discussing emerging therapies, we explore novel approaches to drug development from drug repurposing to in-utero stem cell transplants. We highlight the improved understanding of bone pathophysiology, genetic pathways and challenges of developing gene therapies for GSDs.

Purpose: Fibrodysplasia ossificans progressiva is a rare congenital disorder that causes systemic heterotopic ossification, leading to systemic ankyloses and mobility losses. This study aimed to ascertain the natural history of fibrodysplasia ossificans progressiva., Methods: In addition to the medical history questionnaire, patients aged 16 years and older were asked to complete activities of daily living and quality of life surveys using the Barthel Index, MOS 36-Item Short-Form Health Survey, and Health Assessment Questionnaire. The surveys were conducted over a 4-years period., Results: Of the 15 participating patients, 13 reported swelling during the study period. The Barthel Index and Health Assessment Questionnaire surveys indicated a tendency for questionnaire items related to arm function to reflect early decreases in the activities of daily living. Decreases in activities of daily living functioning were closely related to decreases in the quality of life in physical function domains. Activities of daily living and quality of life were maintained at a similar level to baseline values over the study period (Barthel Index: p = 0.42, MOS 36-Item Short-Form Health Survey: p = 0.43, Health Assessment Questionnaire: p = 0.87)., Conclusions: We obtained longitudinal information relating to natural history on fibrodysplasia ossificans progressiva patients. Implications for rehabilitation Fibrodysplasia ossificans progressiva is a rare congenital disease that causes heterotopic ossification of muscle tissue throughout the body, leading to systemic ankyloses and mobility losses. When the Barthel Index was high and the activities of daily living were relatively stable, the items on the Health Assessment Questionnaire that are related to arm function began to show impairment. Early focus on upper extremity function that includes the use of assistive devices during the period when a patient is still able to perform many activities of daily living is important. Although decreases in activities of daily living functioning were closely related to decreases in the quality of life in the physical function domains, the scores of the domains other than physical function were similar to the national standard score.

Myositis ossificans is a benign, solitary, frequently self-limiting, ossifying soft-tissue mass encountered often in the active sporting population. Typically occurring within skeletal muscle - most often the brachialis, quadriceps and adductor muscle groups - lesions may arise with or without a traumatic history. The exact pathophysiology of these ossifying lesions is still poorly understood. Patients present with localized pain and swelling with loss of range of motion. Plain radiographs may not be able to detect early lesions, which allows for an expanded role of ultrasonography as an early screening modality, despite magnetic resonance imaging remaining the gold standard for imaging of soft tissue masses. Conservative treatment is implemented for most patients with excellent outcomes, with surgical excision being an option for persistent symptoms or progressive disease. Typically, athletes are able to progress to light activity at 2 to 3 months, full activity by 6 months, and back to their preinjury level by 1 year.

The following essays are the personal statements of two remarkable young individuals, Ian Cali and Laura Rossano, who candidly share their perspectives on living life with fibrodysplasia ossificans progressiva (FOP). These essays are excerpts from the opening comments that Ian and Laura delivered at The First and The Second International FOP Association Drug Development Forums in 2014 and 2016, respectively. We present these unedited essays in this special issue of BONE so that physicians, scientists, and researchers everywhere can glimpse the valiant challenges that envelop the lives of all individuals with FOP and can appreciate that diseases are not just biological processes but indelible human experiences. These last words belong to Ian and Laura. Frederick S. Kaplan M.D.; Eileen M. Shore Ph.D.; and Robert J. Pignolo M.D., Ph.D. - Guest Editors., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Fibrodysplasia ossificans progressiva (FOP) is an ultra-rare and devastating disorder characterized by cumulative episodes of progressive heterotopic ossification. It is estimated that there exist 600-700 patients in Mainland China. Nevertheless, due to the rarity, many FOP patients were initially misdiagnosed. Until now fewer than 150 patients have been identified in Mainland China. This review summarizes the epidemiology and clinical features of FOP patients, the progress of clinical and basic research in China, and the future of FOP care in China., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The worldwide prevalence and risk factors for kidney stones in patients with fibrodysplasia ossificans progressiva (FOP) are unknown. We conducted a survey of 383 patient-members of the International Fibrodysplasia Ossificans Progressiva Association, comprising the entire global membership of the international FOP community. Two hundred seven patients from 31 nations and 6 continents (54%) responded. Nineteen of 207 respondents had kidney stones, revealing a worldwide prevalence of 9.2%. In a confirmatory follow-up study of subjects participating in a longitudinal FOP natural history study, 9 of 114 individuals reported a history of kidney stones (7.9%). In both study populations patients with kidney stones were found to be more functionally impaired compared to those without nephrolithiasis. The prevalence of kidney stones in the adult FOP population of the Unites States was 15.8% (9/57 individuals) compared to a sex- and age-weighted prevalence of 4.5% (p=4×10 -5 ) in the general population. Although geographical variation exists, patients with FOP have an approximately three-fold greater prevalence of kidney stones than the general population. This unusually high prevalence may be due to high bone turnover from chronic immobilization, or to unknown mechanistic effects of the activating FOP mutation in activin A receptor, type I/activin-like kinase-2 (ACVR1/ALK2), increasing the disease burden and morbidity in this already disabling condition., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Background: Fibrodysplasia ossificans progressiva (FOP) is a rare, severely disabling, and life-shortening genetic disorder that causes the formation of heterotopic bone within soft connective tissue. Previous studies found that the FOP prevalence was about one in every two million lives. The aim of this study is to estimate the FOP prevalence in France by probabilistic record-linkage of 2 national databases: 1) the PMSI (Programme de médicalisation des systèmes d'information), an administrative database that records all hospitalization activities in France and 2) CEMARA, a registry database developed by the French Centres of Reference for Rare Diseases., Results: Using a capture-recapture methodology to adjust the crude number of patients identified in both data sources, 89 FOP patients were identified, which results in a prevalence of 1.36 per million inhabitants (CI95% = [1.10; 1.68]). FOP patients' mean age was 25 years, only 14.9% were above 40 years, and 53% of them were males. The first symptoms - beside toe malformations- occurred after birth for 97.3% of them. Mean age at identified symptoms was 7 years and above 18 years for only 6.9% of patients. Mean age at diagnosis was 10 years, and above 18 years for 14.9% of the patients. FOP patients were distributed across France., Conclusions: Despite the challenge of ascertaining patients with rare diseases, we report a much higher prevalence of FOP in France than in previous studies elsewhere. We suggest that efforts to identify patients and confirm the diagnosis of FOP should be reinforced and extended at both national and European level.

The formation of lamellar bone in the soft tissues, where bone normally does not exist, is called myositis ossificans. However, it would be more accurate to describe as myositis ossificans the involvement of skeletal muscles and as ectopic or heterotopic ossification the involvement of soft tissues in general. The lesion is subdivided in genetic and non-genetic or acquired types. Myositis or fibrodysplasia ossificans progressiva is a debilitating rare genetic disorder. Clinical suspicion of the disease in the newborn on the basis of malformed great toes may lead to early clinical diagnosis, confirmatory diagnostic genetic testing and avoidance of iatrogenic harmful procedures. Acquired lesions involve the neurogenic myositis ossificans and the non-neurogenic disorder. The latter is defined either as circumscribed myositis ossificans that is post-traumatic or as idiopathic/pseudomalignant myositis ossificans that is non-traumatic and may be a form fruste of fibrodysplasia ossificans progressiva. Ossification in fibrodysplasia ossificans progressiva is irreversible, unlike other forms of heterotopic ossification. In this retrospective study, a total of 22 children with myositis ossificans treated in a 20-year period were identified and classified. Two patients were diagnosed with myositis/fibrodysplasia ossificans progressiva, one with neurogenic myositis ossificans, one with idiopathic/pseudomalignant myositis ossificans and 18 patients with circumscribed myositis ossificans. The clinical features, imaging and histological findings as well as treatment modalities and complications of myositis ossificans in our patients are presented and discussed.

Fibrodysplasia ossificans progressiva (FOP) is a rare congenital disease that causes bone formation within the muscles, tendons, ligaments and connective tissues. There is no cure for this disorder and only treatment of the symptoms is available. The purpose of this study was to review the literature and describe the clinical, cellular and molecular aspects of FOP. The material used for the study was obtained by reviewing scientific articles published in various literature-indexed databases. In view of its rarity and of the lack of insightful information and the unpredictability of its course, FOP is a challenging disorder for professionals who are confronted by it. However, this rare disease raises a great deal of interest because understanding the mechanism of mature bone formation can encourage research lines related to bone regeneration and the prevention of heterotopic ossification.

Fibrodysplasia ossificans progressiva, an ultra-rare and disabling genetic disorder of skeletal malformations and progressive heterotopic ossification (HO), is the most catastrophic condition of skeletal metamorphosis in humans. We studied 72 patients with FOP in China and analyzed their phenotypes and genotypes comprising the world's largest ethnically homogeneous population of FOP patients. Ninety-nine percent of patients (71/72 cases) were of Han nationality; and 1% of patients (1/72 cases) were of Hui nationality. Based on clinical examination, 92% of patients (66/72 cases) had classic FOP; 4% of patients (3/72 cases) were FOP-plus; and 4% of patients (3/72) were FOP variants. Importantly, all individuals with FOP had mutations in the protein-coding region of activin A receptor, type I/activin-like kinase 2 (ACVR1/ALK2). Ninety-seven percent of FOP patients (70/72 cases) had the canonical c.617G>A (p.R206H) mutation, while 3% of FOP patients (2/72 cases) had variant mutations in ACVR1/ALK2. Taken together, the genotypes and phenotypes of individuals with FOP from the Han nationality in China are similar to those reported elsewhere and support the fidelity of this ultra-rare disorder in the world's most highly populated nation and across wide racial, ethnic, gender and geographic distributions., (© 2013.)

Fibrodysplasia ossificans progressiva (FOP), a rare, disabling condition caused by gain-of-function mutations of a bone morphogenetic protein (BMP) type I receptor, leads to episodes of heterotopic ossification and resultant immobility. Neurological problems have not been associated with FOP, but neurological symptoms are commonly reported by FOP patients. To determine the prevalence of neurological symptoms and their characteristics in individuals with FOP, we conducted a survey of the 470 patient members of the International FOP Association (IFOPA) using a questionnaire about neurological symptoms. There were 168 responses (105 females, 63 males; age 1.5-68 years) from 30 countries representing 36 % of IFOPA members. Chronic neurological symptoms were reported by 86 (51 %). Prevalence of neuropathic pain (NP) was significantly increased (P < 0.001) compared to the general population, and tenfold more common in females (15 %) than males (1.6 %). Of those with NP, 94 % reported other sensory abnormalities. Prevalence of recurrent severe headaches (HA) (26 %) was similar to that in the general population, but prevalence in females with FOP (36 %) was almost fourfold greater than in males. Prevalence of NP, HA, and other sensory abnormalities was substantially higher in post-pubertal females; 33 % reported symptoms worsened during menstrual periods. Worsening of neurological symptoms during FOP flare-ups was reported by 23 %. Three patients with FOP (1.8 %) reported myoclonus, a prevalence much greater than reported in the general population (P < 0.001). Our worldwide survey indicates that neurological symptoms are common in FOP. We speculate that these symptoms are related to effects of dysregulated BMP signaling on the central and/or peripheral nervous systems.

We aimed to investigate the epidemiological determinants, clinical features, and genetic pattern of FOP in our country by evaluating the entire population of patients identified according to a combination of methods. To achieve this, 24 individuals were confirmed as FOP cases, 17 of whom were alive at the end of 2011 (point prevalence=0.36 × 10(-6)). The gender distribution (male/female ratio=13/11) and the concurrent range of ages (from 4 to 53 years; mean ± SD: 30.2 ± 13.8) are in agreement with similar reports. Twenty-one (87.5%) had characteristic congenital malformations of the big toe, and short thumbs were found in 65.2% of cases. In addition, other skeletal malformations such us fusion of the posterior elements of the cervical spine (89.0%), knee osteochondromas (71%), scoliosis (54.5%), and short and broad femoral neck (52.6%) were observed. All had developed mature ossicles of heterotopic bone in typical anatomic and temporal patterns, ranging in number from 1 to 17 (9.5 ± 3.9). Age at appearance of first ossifying lesion varied from 3 months to 15 years. Mean age at diagnosis was 7.3 ± 5.1 years and the average delay in reaching the correct diagnosis after the onset of heterotopic ossification was 2.7 years (range=0-12 years). Biopsy of the pre-osseous lesions was performed in 11 of 20 (55.0%), providing no useful information for the diagnosis of FOP. Seven of 18 (38.9%) reported some hearing loss, and 5 (27.8%) experienced diffuse thinning of the hair or were bald. No patient had relatives with a typical FOP clinical picture. Fourteen of the 16 cases which were genetically investigated displayed the single heterozygous mutation c.617G>A in exon 4 of the ACVR1 gene. One of the two patients who did not present with the canonical ACVR1 mutation showed a heterozygous mutation c.774G>C in exon 5 leading to the substitution of Arginine 258 with a serine. The other patient had a heterozygous c.774G>T substitution in exon 5 leading to the same amino acid change (p.Arg258Ser). These two patients had only nonspecific abnormalities of the great toe, lacked the typical anatomic and developmental pattern of heterotopic ossification, and shared a trend toward uncommon clinical features. These results provide new insight on the epidemiological and clinical traits of FOP, reinforcing the notion of its worldwide homogeneity. The molecular characterization of ACVR1 sequence variation will contribute to the understanding of the genetic profile of this devastating disease in different geographical areas., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Fibrodysplasia ossificans progressiva (FOP) is a severely disabling heritable disorder of connective tissue characterized by congenital malformations of the great toes and progressive heterotopic ossification that forms qualitatively normal bone in characteristic extraskeletal sites. The worldwide prevalence is approximately 1/2,000,000. There is no ethnic, racial, gender, or geographic predilection to FOP. Children who have FOP appear normal at birth except for congenital malformations of the great toes. During the first decade of life, sporadic episodes of painful soft tissue swellings (flare-ups) occur which are often precipitated by soft tissue injury, intramuscular injections, viral infection, muscular stretching, falls or fatigue. These flare-ups transform skeletal muscles, tendons, ligaments, fascia, and aponeuroses into heterotopic bone, rendering movement impossible. Patients with atypical forms of FOP have been described. They either present with the classic features of FOP plus one or more atypical features [FOP plus], or present with major variations in one or both of the two classic defining features of FOP [FOP variants]. Classic FOP is caused by a recurrent activating mutation (617G>A; R206H) in the gene ACVR1/ALK2 encoding Activin A receptor type I/Activin-like kinase 2, a bone morphogenetic protein (BMP) type I receptor. Atypical FOP patients also have heterozygous ACVR1 missense mutations in conserved amino acids. The diagnosis of FOP is made by clinical evaluation. Confirmatory genetic testing is available. Differential diagnosis includes progressive osseous heteroplasia, osteosarcoma, lymphedema, soft tissue sarcoma, desmoid tumors, aggressive juvenile fibromatosis, and non-hereditary (acquired) heterotopic ossification. Although most cases of FOP are sporadic (noninherited mutations), a small number of inherited FOP cases show germline transmission in an autosomal dominant pattern. At present, there is no definitive treatment, but a brief 4-day course of high-dose corticosteroids, started within the first 24 hours of a flare-up, may help reduce the intense inflammation and tissue edema seen in the early stages of the disease. Preventative management is based on prophylactic measures against falls, respiratory decline, and viral infections. The median lifespan is approximately 40 years of age. Most patients are wheelchair-bound by the end of the second decade of life and commonly die of complications of thoracic insufficiency syndrome.

Fibromyalgia ossificans progressiva (FOP) is a severely disabling disorder of connective tissue characterized by congenital malformation of the toes, fingers and vertebrae associated with progressive ossification of striated muscles. Anesthetic management of these patients involves preferably general anesthesia as local or regional anesthesia should be avoided due to possible heterotopic ossification. Airway management is determined by the age of the patient and the progression of the disease. Only a few cases in the literature have reported the anesthetic management of FOP patients and to our knowledge only one case has been published on pediatric patients. In adult, cooperative patients awake fiberoptic intubation is recommended, as ankylosis of the temporo-mandibular joint is the most important clinical feature for anesthesia. As demonstrated and discussed in this case report of a 2-year-old boy, fiberoptic intubation after induction of general anesthesia should be preferred in pediatric patients. Puncture of a vein should be non-traumatic, i.m. injections strictly avoided and careful positioning and padding are needed. Every effort should be made to avoid situations stimulating new heterotopic ossification due to its substantial effect on the quality of life of FOP patients.

Osteochondrodysplasias like thanatophoric dysplasia, osteogenesis imperfecta, achondroplasia, and other genetic skeletal disorders like fibrodysplasia ossificans progressiva are infrequently seen in clinical practice. In cases of sporadic achondroplasia as well as in fibrodysplasia ossificans progressiva, there is a strong association with paternal age, a relationship that is less evident in other genetic osteochondral diseases. No other constitutional or environmental factor has proven to be associated with these disorders. The use of prenatal ultrasonography as a routine component of prenatal care is crucial in the early suspicion of osteochondrodysplasias whereas definitive diagnosis is usually obtained by pre-natal molecular analysis. In the case of fibrodysplasia ossificans progressiva, recognition of congenital great toe malformations associated with rapidly-appearing soft tissue swelling is sufficient to make the proper clinical diagnosis, which can be confirmed by genetic testing. Large regional centres will improve diagnosis performance, provide accurate genetic counselling, and ensure an integral assistance for these often severe and incapacitating conditions.

Fibrodysplasia ossificans progressiva (FOP) is a rare but very severe disease, characterised by congenital malformations of the toes and by progressive heterotopic ossification of muscles and joints. Two genes, the noggin (NOG) gene and the activin A type I receptor (ACVRI) gene, are involved in FOP. In this study we have searched for the NOG and the 617G>A (ACVR1) mutations in a well characterized series of twenty-seven French FOP patients. Five NOG mutations (delta 42, 274G>C, 275G>A, 276G>A, and 283G>A) have been found in seven (26%) of our FOP patients. The 617G>A mutation in the ACVR1 gene is found in fourteen (52%) of the patients. With one exception (patient number 22), 617G>A and NOG mutations are mutually exclusive in patients. Mutations 274G>C, 283G>A and 617G>A segregate with the trait in five different FOP families, some members of them being partially affected by the disease.

Metamorphosis, the transformation of one normal tissue or organ system into another, is a biological process rarely studied in higher vertebrates or mammals, but exemplified pathologically by the extremely disabling autosomal dominant disorder fibrodysplasia ossificans progressiva (FOP). The recurrent single nucleotide missense mutation in the gene encoding activin receptor IA/activin-like kinase-2 (ACVR1/ALK2), a bone morphogenetic protein type I receptor that causes skeletal metamorphosis in all classically affected individuals worldwide, is the first identified human metamorphogene. Physiological studies of this metamorphogene are beginning to provide deep insight into a highly conserved signaling pathway that regulates tissue stability following morphogenesis, and that when damaged at a highly specific locus (c.617G > A; R206H), and triggered by an inflammatory stimulus permits the renegade metamorphosis of normal functioning connective tissue into a highly ramified skeleton of heterotopic bone. A comprehensive understanding of the process of skeletal metamorphosis, as revealed by the rare condition FOP, will lead to the development of more effective treatments for FOP and, possibly, for more common disorders of skeletal metamorphosis.

Heterotopic ossification, the formation of bone in soft tissue, requires inductive signaling pathways, inducible osteoprogenitor cells, and a heterotopic environment conducive to osteogenesis. Little is known about the molecular pathogenesis of this condition. Research into two rare heritable and developmental forms, fibrodysplasia ossificans progressiva and progressive osseous heteroplasia, has provided clinical, pathologic, and genetic insights. In fibrodysplasia ossificans progressiva, overexpression of bone morphogenetic protein 4 and underexpression of multiple antagonists of this protein highlight the potential role of a potent morphogenetic gradient. Research on fibrodysplasia ossificans progressiva also has led to the identification of the genetic cause of progressive osseous heteroplasia: inactivating mutations in the alpha subunit of the gene coding for the stimulatory G protein of adenylyl cyclase. Better understanding of the complex developmental and molecular pathology of these disorders may lead to more effective strategies to prevent and treat other, more common forms of heterotopic ossification.

Inherited ossifying diseases are relatively uncommon diseases leading ta a great disability and life-threatening complications. Fibrodysplasia Ossificans Progressiva is characterized by the association of skeletal abnormalities mainly in great toes, and enchondral ossifications in tendons and muscles. BMP dysregulation seems to be the main underlying mechanism of the heterotopic ossifications. The genetic basis remain controversial between a mutation on chromosome 4 or 17. Progressive Osseous Heteroplasia (HOP), more recently described, shares some similarities with Albrights hereditary osteodystrophy. In HOP, the intramembranous ossifications progressively developped from the dermis to the deeper layer. The genetic abnormality involved the GNAS 1 gene leading to an inactivation of the alpha subunit of the G protein-complex. Some therapeutic approaches have been tried: angiogenesis inhibition, mast cell inhibition; others remained in project: BMP 4 inhibition; actually there is no proved efficacy of any of them.

Heterotopic ossification, or myositis ossificans, denotes true bone in an abnormal place. The pathogenic mechanism is still unclear. A total of 643 patients (mean age, 9.1 years) admitted for neuropediatric rehabilitation were analyzed retrospectively with respect to the existence of neurogenic heterotopic ossification. The purpose of this study was to obtain information about incidence, etiology, clinical aspect, and consequences for diagnosis and therapy of this condition in childhood and adolescence. Heterotopic ossification was diagnosed in 32 patients (mean age, 14.8 years) with average time of onset of 4 months after traumatic brain injury, near drowning, strangulation, cerebral hemorrhage, hydrocephalus, or spinal cord injury. The sex ratio was not significant. In contrast to what has been found in adult studies, serum alkaline phosphatase was not elevated during heterotopic ossification formation. A persistent vegetative state for longer than 30 days proved to be a significant risk factor for heterotopic ossification. The incidence of neurogenic heterotopic ossification in children seems to be lower than in adults. A genetic predisposition to heterotopic ossification is suspected but not proven. As a prophylactic regimen against heterotopic ossification we use salicylates for those patients in a coma or persistent vegetative state with warm and painful swelling of a joint and consider continuous intrathecal baclofen infusion and botulinum toxin injection for those patients with severe spasticity. We prefer to wait at least 1 year after trauma before excision of heterotopic ossification.

Progressive heterotopic ossification leads to ankylosis of the major joints in patients who have fibrodysplasia ossificans progressiva. Joint subluxation has not been recognized widely in patients with this disease. The clinical records and radiographs of 79 patients with fibrodysplasia ossificans progressiva were reviewed and, it was found that humeral to chest wall synostosis and subluxation of the glenohumeral joint had occurred in 21% of skeletally immature patients and in 74% of skeletally mature patients. In fibrodysplasia ossificans progressiva, synostosis of the humeral shaft to the chest wall commonly occurs by 7 years of age, well before the age of proximal physeal closure. The continued growth of the proximal humeral physis in the presence of a humeral to chest wall synostosis causes the humeral head to migrate superiorly, thus promoting growth related subluxation. The clinical significance of this finding for patients who have fibrodysplasia ossificans progressiva is unknown, but this unique model will be useful in the study of shoulder biomechanics and growth plate physiology.

We reviewed roentgenograms and clinical records in order to characterize the spinal deformity in forty patients who had an established diagnosis of fibrodysplasia ossificans progressiva. Twenty-six (65 per cent) of the patients had scoliosis, which, according to the clinical records and the recollection of the patients, had been present during childhood. Twenty-three (88 per cent) of the twenty-six curves were unbalanced c-shaped curves, while the remaining three (12 per cent) were balanced s-shaped curves. Twenty-one (91 per cent) of the twenty-three c-shaped curves involved the thoraco-lumbar or lumbar spine. The c-shaped curves ranged in magnitude from 15 to more than 80 degrees. Curves became rigid by early adulthood and many resulted in severe pelvic obliquity with impaired sitting or standing balance. An osseous bridge developed between the posterolateral aspect of the iliac crest and the posterolateral aspect of the rib cage in twenty-two (55 per cent) of the forty patients. Nineteen (86 per cent) of these twenty-two patients had scoliosis; there was a significant association between the development of scoliosis and the presence of the osseous bridge (p < 0.005). Ossification of the paravertebral muscles and fascia during the first decade of life limited the development of a normal thoracic kyphosis in ten (42 per cent) of twenty-four patients for whom lateral roentgenograms of the spine were available. A spinal orthosis was used to treat the scoliosis in two patients, but this method resulted in breakdown of the skin and failed to halt progression of the curve.(ABSTRACT TRUNCATED AT 250 WORDS)

This is a report on 14 patients with myositis ossificans with simultaneous head injury. Predilected sites are the hip and elbow joints as well as thigh musculature, where particularly in the youthful and younger adults ossifications occur 5--8 weeks after the accident. Premature operative treatment is useless because of the danger of recurrence. The process of ossification usually comes to a standstill 8--12 weeks following the trauma. The diagnosis is made on the basis of clinical examination (hardening of muscles, immobility of joints) and X-ray pictures. The pathogenesis and modes of therapy are discussed in detail. Furthermore, the incidence of this complication of head injury in various age groups is evaluated statistically.

A bone block transfer of coracoacromial ligament into the medullary canal of the clavicle for Grade III acromioclavicular injury was developed in an attempt to prevent occasional pullout of the ligament in the procedure described by Weaver and Dunn. Fifteen consecutive cases (12 acute, three chronic) with Grade III acromioclavicular injury were treated by this method. All but one patient regained painless full range of shoulder motion. All patients returned to previous activity. Failure of coracoclavicular reconstruction occurred in one case. Asymptomatic focal myositis ossificans developed in four cases with no functional deficit.