Iatrogenic harm caused by diagnostic errors in fibrodysplasia ossificans progressiva

Stone man: a case report

Fibrodysplasia ossificans progressiva (FOP) is a rare hereditary connective tissue disease characterized by the progressive ectopic ossification of ligaments, tendons, and facial and skeletal muscles throughout life. Symptoms begin in childhood as localized soft tissue swellings. Immobility and articular dysfunction appear with involvement of the spine and proximal extremities. The temporomandibular joint (TMJ) is a critical component involved in the maxillofacial region, resulting in severe limitation of masticatory function, although TMJ involvement is rare. The aim of this article is to present a 28-year-old man with dental problems and slowly progressive limitation of motion in the jaw, knees, shoulders and hips as well as neck distortion.

Fibrodysplasia ossificans progressiva in Spain: epidemiological, clinical, and genetic aspects

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.

The stone man disease: fibrodysplasia ossificans progressiva: imaging revisited

Fibrodysplasia ossificans progressiva (FOP) is a rare, disabling connective tissue disorder of unknown aetiology. Its occurrence is usually sporadic but may be an inherited autosomal-dominant condition with wide range of expression. FOP is characterised by congenital malformations of the great toes and abnormal progressive heterotopic ossification of striated muscles, tendons, ligaments, fascia and aponeuroses of the trunk and extremities leading to painful swellings. The ossifications typically appear within the first decade of life, resulting in progressive morbidity and severe disability. So far, there has been no effective treatment or prevention. In the early localised phase of disease it may be misdiagnosed, hence the role of correct diagnosis through imaging is essential. Herein, we report a case of a 10-year-old female who was evaluated radiologically and diagnosed as a case of FOP. The findings of plain radiography are described and the role of CT is highlighted.

Neurological symptoms in individuals with fibrodysplasia ossificans progressiva

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.

Unusually severe limitation of the jaw attributable to fibrodysplasia ossificans progressiva: a case report with cone-beam computed tomography findings

Fibrodysplasia ossificans progressiva (FOP) is a rare hereditary connective tissue disease characterized by the progressive ectopic ossification of ligaments, tendons, and facial and skeletal muscles throughout life. Symptoms begin in childhood as localized soft tissue swellings. Immobility and articular dysfunction appear with involvement of the spine and proximal extremities. The temporomandibular joint (TMJ) is a critical component involved in the maxillofacial region, resulting in severe limitation of masticatory function, although TMJ involvement is rare. We report a case of FOP presenting as severely limited TMJ movements owing to ectopic calcification of the left coronoid process. In addition to the clinical examination, panoramic radiography and cone-beam computed tomography images were obtained. The case is presented and the clinical and imaging findings, differential diagnosis, and treatment modalities are discussed.

Fibroblastic and myofibroblastic tumors in children and adolescents

Fibroblastic and myofibroblastic tumors in children and adolescents are a relatively common group of soft tissue proliferations that range from reactive to hamartomatous to neoplastic, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic and immunohistochemical overlap, despite significant clinical, genetic, and prognostic differences. The fibromatoses are a major subgroup, and all types of fibromatoses can occur in the 1st 2 decades of life. Intermediate and malignant fibroblastic-myofibroblastic tumors are an important group that includes variants of fibrosarcoma and other tumors with recurrent cytogenetic or molecular genetic abnormalities and low metastatic potential. Pathologic examination is enhanced by adjunct techniques, such as immunohistochemistry, cytogenetics, and molecular genetics, although morphology provides the ultimate criteria for a specific diagnosis. This article reviews the clinicopathologic features of fibroblastic and myofibroblastic tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents, the use of diagnostic adjuncts, and differential diagnoses.

Fibrodysplasia ossificans progressiva

Bei der Fibrodysplasia ossificans progressiva (FOP) handelt es sich um eine sehr seltene, autosomal-dominant vererbbare Erkrankung, die durch Ausbildung von heterotopen Ossifikationen charakterisiert ist, welche zu einer ausgeprägten Mobilitätseinschränkung führen. Angeborene Fehlbildungen von Großzehen im Sinne von Hypoplasie und fibularer Deviation werden bei den meisten Patienten beschrieben. Eine Hypoplasie der Daumen besteht bei etwa der Hälfte der Patienten. Als genetische Ursache der FOP wurden heterozygote Mutationen im ACVR1-Gen identifiziert. Wir berichten über die klinischen und molekulargenetischen Daten von 25 eigenen Patienten (3 bereits veröffentlicht) und weiteren 47 Patienten aus der Literatur mit bekannten Mutationen, bei denen klinische Daten vorlagen und stellen eine Genotyp-Phänotyp-Korrelation dar.

Fibrodysplasia ossificans progressiva: middle-age onset of heterotopic ossification from a unique missense mutation (c.974G>C, p.G325A) in ACVR1

Fibrodysplasia ossificans progressiva (FOP) is the rare mendelian disease characterized by congenital malformation of the great toes preceding heterotopic ossification (HO) and caused by heterozygous activating mutation of the ACVR1 gene, which encodes the ALK2 receptor for bone morphogenetic proteins. Early adult life is the latest reported presentation for the HO of FOP. The patient of our report first developed HO from FOP at 47 years of age. She had congenital hallux valgus deformity but despite various traumas was previously well. HO began several months after a brief, seemingly viral, illness. Sudden and progressive pain, redness, warmth, and swelling appeared over a scapula. Computed tomography was remarkable for asymmetrical thickening of muscles and fascial planes. At first, the significance of the great toe abnormalities went unrecognized elsewhere, and biopsy for suspected inflammatory fasciitis revealed proliferating fibroblasts with scattered inflammatory cells. Prednisone improved her symptoms but, when tapered, swellings developed on her chest, posterior thorax, and flank, and FOP was diagnosed. Methylprednisolone, methotrexate, and alendronate seemed to help her symptoms, but the lesions worsened and HO appeared and rapidly progressed. Mutation analysis of the ACVR1 gene revealed heterozygosity for a unique missense defect (c.974G>C, p.G325A) that predicted a conservative (mild) amino acid change within the kinase domain of ALK2. Hence, HO in FOP can be delayed until middle-age, and perhaps provoked by a viral illness. Nevertheless, progression of HO can then be rapid despite bisphosphonate and high-dose immunosuppressive therapy. Possibly, our patient's late-onset HO reflects her mild alteration of ALK2 or some protective and therapeutically useful genetic, epigenetic, or nongenetic factor. Recognition of presymptomatic individuals or late-onset HO in FOP should have these patients avoid traumas, treatments, and maybe viral illnesses that can initiate or exacerbate the HO. If the diagnosis of FOP is unclear, ACVR1 mutation analysis is available at certified laboratories.

Pregnancy in fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare disabling genetic disorder characterized by progressive postnatal heterotopic ossification leading to cumulative disability. Heterotopic bone formation in FOP usually begins in early childhood following a series of painful, post-traumatic, inflammatory soft-tissue swellings known as flare-ups, which later undergo ossification resulting in the progressive immobilization of the chest wall, limbs and jaw by early adulthood. Pregnancy in FOP has occurred infrequently and reproductive decisions are a dilemma for an individual or couple with FOP. We present the clinical course, medical management and potential concerns of four cases of pregnancy in FOP.

Fibrodysplasia ossificans progressiva: clinical and genetic aspects

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.

PROGRESSIVE OSSIFYING FIBRODYSPLASIA: CASE REPORT

Progressive ossifying fibrodysplasia is a rare genetic disease that affects one individual in every two million births. Its main consequence is heterotopic ossification, i.e. formation of additional bone in abnormal locations. It is an autosomal dominant disease, usually caused by a new mutation in the ACVR1 receptor gene, which is in the signaling pathway for bone morphogenic protein. This abnormality is not related to gender, ethnicity or consanguinity. The present study reports the case of A.C., a 17-year-old girl. Her clinical investigation began at the age of four years, but she was only diagnosed with FOP at the age of 15 years, after being evaluated by several specialists in different centers. The patient has two siblings, but her family history did not reveal any similar cases.

Fibrodysplasia ossificans progressiva: report of a case and review of articles

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder, characterized by painful swelling of muscles and connective tissue in the early years of life, consequently leading to ossification at a mean age of 4-5 years. We report FOP in a 2-year-old boy with palpable masses in the frontal and lower cervical paraspinal and left periscapular muscles.He was born with hallux valgus. Despite this hallmark, he was referred to the hospital with the primary diagnosis of hematoma, but further investigation indicated FOP. The patient was discharged from the hospital with non steroidal anti-inflammatory drugs (NSAID) and education of the parents. The importance of this case was that in spite of the early occurrence of the typical presentation of FOP for more than one year and the fact that the patient's mother was a physician who had consulted with many specialists, the diagnosis had been missed.This indicates that the general physicians, radiologists and other specialists' awareness and knowledge of FOP is insufficient.

Scalp nodules as a presenting sign of fibrodysplasia ossificans progressiva: a register-based study

BACKGROUND

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by progressive ossification of soft tissues. Clinical diagnosis is important because trauma from lesional biopsies can exacerbate the disease.

OBJECTIVE

We sought to evaluate the frequency of scalp nodules as the presenting manifestation of FOP.

METHODS

We describe 3 infants with FOP who presented with multiple neonatal scalp nodules. We reviewed all 43 cases of this disorder in the French FOP registry.

RESULTS

Scalp nodules were found in 40% of cases and usually represented the first manifestation of the disease. All 43 patients had characteristic skeletal malformations involving the great toes (n = 43), fingers (n = 12), and vertebrae (n = 3). Other abnormalities were cerebral malformations (n = 1) and alopecia (n = 2). Histopathologic analysis did not contribute to the differential diagnosis and was interpreted as cranial fasciitis in two patients.

LIMITATIONS

Our study was retrospective, and the presence or absence of scalp nodules was not always recorded.

CONCLUSION

Neonatal scalp nodules associated with a characteristic malformation of the great toes are a common presentation of FOP. Physicians should be aware that lesional biopsies can exacerbate the disease and must therefore be avoided. A diagnosis of classic FOP can be confirmed by molecular genetic studies.

Fibrodysplasia ossificans progressiva (FOP): watch the great toes!

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder and the most disabling condition of heterotopic (extraskeletal) ossification in humans. Extraskeletal bone formation associated with inflammation preceding the osseous conversion usually begins in the first decade, predominantly in the head, neck, and shoulders. All patients have malformed great toes. Most patients have a spontaneous mutation of the ACVR1 gene. We report a 17-year-old girl with malformed great toes who had her first episode of heterotopic ossification and impaired mobility of the left hip at the age of 13 years. No inflammatory fibroproliferative masses preceded the onset of heterotopic ossification. Radiographic studies demonstrated myositis ossificans, but failure to associate the great toe malformation with heterotopic ossification led to a failure to diagnose FOP. She underwent repeated and unnecessary operative procedures to remove a recurrent lesion. FOP was finally suspected when the great toe malformation was correlated with the trauma-induced heterotopic ossification. Genetic analysis confirmed the presence of the classic FOP mutation (ACVR1 c.617G>A; R206H). This case highlights the importance of examining the great toes in anyone with heterotopic ossification. The association of malformations of the great toe with heterotopic ossification in all cases of classic FOP will lead to prompt clinical diagnosis and the prevention of iatrogenic harm.

Deformity of the great toe in fibrodysplasia ossificans progressiva

BACKGROUND

As invasive medical procedures can induce permanent heterotopic ossification in fibrodysplasia ossificans progressiva (FOP), caution should be exercised in clinical practice. The present study was conducted to examine the characteristics of the great toe deformity in patients with FOP, which may lead to an early diagnosis of this condition.

METHODS

The subjects consisted of 31 feet from 16 FOP patients (8 males, 8 females) with an average age of 17.3 years (range 1-47 years) at the time of this study. Gross and radiographic findings, including the hallux valgus angles (HVA), intermetatarsal angles (IMA), and the deformity of the proximal phalanx and metatarsal bone, were examined.

RESULTS

Of the 31 feet, 29 (93.5%) showed several degrees of great toe deformity. A shortened great toe was the typical gross finding and was observed in 20 feet (64.5%). The mean HVA and IMA were 19.7° and 8.5°, respectively; and 22 (71.0%) feet satisfied the radiographic definition of hallux valgus (HVA ≥ 20° or IMA ≥ 10°). The proximal phalanx was consistently shortened but morphologically dissimilar from case to case. The metatarsal bone was also shortened and sharpened to the medial side, deviating the proximal phalanx laterally from the metatarsal axis. Fusion between the distal and proximal phalanx occurred with advancing age. Only two feet in one patient showed no obvious deformity of the great toe.

CONCLUSIONS

A shortened great toe and hallux valgus were frequently found in patients with FOP. Shortening and sharpening of the proximal phalanx and metatarsal bone consistently existed and contributed to the great toe deformity. These findings were thought to exist from birth and may be a key to an early diagnosis.

Molecular consequences of the ACVR1(R206H) mutation of fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP), a rare genetic and catastrophic disorder characterized by progressive heterotopic ossification, is caused by a point mutation, c.617G>A; p.R206H, in the activin A receptor type 1 (ACVR1) gene, one of the bone morphogenetic protein type I receptors (BMPR-Is). Although altered BMP signaling has been suggested to explain the pathogenesis, the molecular consequences of this mutation are still elusive. Here we studied the impact of ACVR1 R206H mutation on BMP signaling and its downstream signaling cascades in murine myogenic C2C12 cells and HEK 293 cells. We found that ACVR1 was the most abundant of the BMPR-Is expressed in mesenchymal cells but its contribution to osteogenic BMP signal transduction was minor. The R206H mutant caused weak activation of the BMP signaling pathway, unlike the Q207D mutant, a strong and constitutively active form. The R206H mutant showed a decreased binding affinity for FKBP1A/FKBP12, a known safeguard molecule against the leakage of transforming growth factor (TGF)-beta or BMP signaling. The decreased binding affinity of FKBP1A to the mutant R206H ACVR1 resulted in leaky activation of the BMP signal, and moreover, it decreased steady-state R206H ACVR1 protein levels. Interestingly, while WT ACVR1 and FKBP1A were broadly distributed in plasma membrane and cytoplasm without BMP-2 stimulation and then localized in plasma membrane on BMP-2 stimulation, R206H ACVR1 and FKBP1A were mainly distributed in plasma membrane regardless of BMP-2 stimulation. The impaired binding to FKBP1A and an altered subcellular distribution by R206H ACVR1 mutation may result in mild activation of osteogenic BMP-signaling in extraskeletal sites such as muscle, which eventually lead to delayed and progressive ectopic bone formation in FOP patients.

Early mortality and cardiorespiratory failure in patients with fibrodysplasia ossificans progressiva

BACKGROUND

Fibrodysplasia ossificans progressiva, a rare genetic disorder of progressive extraskeletal ossification, is the most disabling form of heterotopic ossification in humans. However, little is known about the lifespan or causes of mortality in these patients. We undertook this study to determine the lifespan and causes of mortality in individuals who had fibrodysplasia ossificans progressiva.

METHODS

We reviewed comprehensive mortality reports from two large registries of patients with fibrodysplasia ossificans progressiva. Together, these registries comprise >90% of all known patients with this condition in the world. We noted the sex, dates of birth and death, and the cause of death for each individual. We verified the cause of death with extensive medical records, when available. We also collected date of birth, current age, and sex information for each living patient member of the International Fibrodysplasia Ossificans Progressiva Association.

RESULTS

Sixty deaths (thirty male and thirty female patients) were reported in the fibrodysplasia ossificans progressiva community during a thirty-three-year-period. For all sixty patients, the median age at the time of death was forty years (range, three to seventy-seven years). Data were sufficient to establish the cause of death in forty-eight (80%) of the sixty individuals. The median age at the time of death for the forty-eight patients (twenty-four male and twenty-four female patients) with an established cause of death was also forty years. The median lifespan estimated from the 371 individuals in the international fibrodysplasia ossificans progressiva community who were alive and the sixty who had died was fifty-six years (95% confidence interval, fifty-one to sixty years). The most common causes of death in patients with fibrodysplasia ossificans progressiva were cardiorespiratory failure from thoracic insufficiency syndrome (54%; median age, forty-two years) and pneumonia (15%; median age, forty years).

CONCLUSIONS

Fibrodysplasia ossificans progressiva is not only an extremely disabling disease but also a condition of considerably shortened lifespan. The most common cause of death in patients with fibrodysplasia ossificans progressiva is cardiorespiratory failure from thoracic insufficiency syndrome.

Mutation Analysis and Prenatal Exclusion of Fibrodysplasia Ossificans Progressiva in a Chinese Fetus

Aims: Fibrodysplasia ossificans progressiva (FOP) is a rare and severely disabling autosomal dominant disorder characterized by congenital malformations of the great toes and progressive postnatal heterotopic ossification. A point mutation in the activin receptor IA (ACVR1) gene is the cause of FOP. Most of the reported cases of FOP are sporadic and caused by de novo mutations; however, some rare cases can also result from parental germline mosaicism associated with a greater risk of recurrence in successive pregnancies. Therefore, once the pathogenic mutation has been identified in the proband, it is relative cheaper and important to perform prenatal diagnostic tests to exclude the recurrence risk of FOP in subsequent pregnancies. In this study, we first investigated the mutation in the ACVR1 gene in a Chinese FOP patient and then performed prenatal tests to exclude the risk of recurrence in the patient's unborn sibling. Methods: A couple visited our clinic with their 4-year-old son, who was clinically diagnosed with FOP, for genetic counseling. Genetic testing was performed by amplifying all the nine exons of the ACVR1 gene using the conventional polymerase chain reaction. Further, DNA sequencing was used to determine the mutation based on the results of a mutation screening using denaturing high-performance liquid chromatography. Subsequently, a prenatal test was performed using the same technique as that used for the proband. Results: A recurrent single nucleotide mutation c.617 G>A (R206H) of the ACVR1 gene was identified in the patient; however, both the parents had a normal ACVR1 gene. Prenatal tests showed that the fetus did not carry the pathogenic mutation. Conclusion: The results confirmed that a recurrent single nucleotide mutation c.617 G>A (R206H) was the genetic cause of FOP and explored the utility of prenatal testing in excluding the risk of recurrence in the successive pregnancy.

Osteochondral diseases and fibrodysplasia ossificans progressiva

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.

The FOP metamorphogene encodes a novel type I receptor that dysregulates BMP signaling

The ability of mature organisms to stabilize phenotypes has enormous selective advantage across all phyla, but the mechanisms have been largely unexplored. Individuals with fibrodysplasia ossificans progressiva (FOP), a rare genetic disorder of progressive heterotopic ossification, undergo a pathological metamorphosis in which one normal tissue is transformed into another through a highly regulated process of tissue destruction and phenotype reassignment. This disabling metamorphosis is mediated by the FOP metamorphogene, which encodes a mutant bone morphogenetic protein (BMP) type I receptor that exhibits mild constitutive activity during development and severe episodic dysregulation postnatally. The discovery of the FOP metamorphogene reveals a highly conserved target for drug development and identifies a fundamental defect in the BMP signaling pathway that when triggered by injury and inflammation transforms one tissue into another.

Mutational screening of ACVR1 gene in Brazilian fibrodysplasia ossificans progressiva patients

Fibrodysplasia ossificans progressiva (FOP) is a severe genetic disorder reported worldwide. A specific heterozygous mutation (c.617G> A; p.R206H) in the activin A type I receptor gene (ACVR1) is regarded as the genetic cause of FOP in all classically affected individuals worldwide. However, a few patients with FOP variants harbor distinct mutations in ACVR1. We screened a group of FOP Brazilian population for mutations in ACVR1. Of 16 patients with a classic FOP phenotype (10 males and 6 females, age range of 3-42 years), all had the classic mutation (p.R206H). One 21-year-old woman with a variant FOP phenotype had the previously reported c.983G> A mutation (p.G328E). Our study contributes to the understanding of the predominant FOP phenotype and genotype and suggests that variant FOP phenotypes are associated with specific mutations in ACVR1 gene.

PET/CT of fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is an exceedingly rare genetic disorder of connective tissue characterized by extensive and irreversible heterotopic ossification of soft-tissue masses that develop in response to inflammation or trauma. Successful management relies on preventative measures and avoidance of invasive procedures such as intramuscular injections and biopsies. Early diagnosis can prevent extensive heterotopic ossification and is possible with recognition of the classic clinical findings in the feet in association with rapidly evolving soft-tissue masses of the trunk and extremities. Unfortunately, in 87% of the 269 previously reported cases, the diagnosis was not considered initially. Patients are often subjected to biopsy of the soft-tissue masses. The pathology of the fibrodysplasia ossificans progressiva is often confused with sarcoma. These patients might be imaged with PET as part of a standard oncological work-up. We present the first reported PET/CT images of a patient with FOP in order to alert radiologists to this diagnostic pathway. Awareness of the disorder might prevent further unnecessary interventions that can lead to extensive deformity and suffering.

ACVR1 gene mutation in sporadic Korean patients with fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP; OMIM 135100) is a rare but extremely disabling genetic disorder of the skeletal system, and is characterized by the progressive development of ectopic ossification of skeletal muscles and subsequent joint ankylosis. The c.617G>A; p.R206H point mutation in the activin A type I receptor (ACVR1) gene has been reported to be a causative mutation of FOP. In the present study, mutation analysis of the ACVR1 gene was performed in 12 patients diagnosed or suspected to have FOP. All patients tested had a de novo heterozygous point mutation of c.617G>A; p.R206H in ACVR1. Mutation analysis confirmed a diagnosis of FOP in patients with ambiguous features, and thus, could be used for diagnostic purposes. Early confirmation through mutation analysis would allow medical professionals to advise on the avoidance of provoking events to delay catastrophic flare-ups of ectopic ossifications.

Fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP), a rare and disabling genetic condition of congenital skeletal malformations and progressive heterotopic ossification (HO), is the most catastrophic disorder of HO in humans. Episodic disease flare-ups are precipitated by soft tissue injury, and immobility is cumulative. Recently, a recurrent mutation in activin receptor IA/activin-like kinase 2 (ACVR1/ALK2), a bone morphogenetic protein (BMP) type I receptor, was reported in all sporadic and familial cases of classic FOP, making this one of the most highly specific disease-causing mutations in the human genome. The discovery of the FOP gene establishes a critical milestone in understanding FOP, reveals a highly conserved target for drug development in the transforming growth factor (TGF)-beta/BMP signalling pathway, and compels therapeutic approaches for the development of small molecule signal transduction inhibitors for ACVR1/ALK2. Present management involves early diagnosis, assiduous avoidance of iatrogenic harm, and symptomatic amelioration of painful flare-ups. Effective therapies for FOP, and possibly for other common conditions of HO, may potentially be based on future interventions that block ACVR1/ALK2 signalling.

Early diagnosis of fibrodysplasia ossificans progressiva

BACKGROUND

Fibrodysplasia ossificans progressiva is a rare and disabling genetic condition characterized by congenital malformation of the great toes and by progressive heterotopic ossification in specific anatomic patterns. Most patients with fibrodysplasia ossificans progressiva are misdiagnosed early in life before the appearance of heterotopic ossification and undergo diagnostic procedures that can cause lifelong disability. Recently, the genetic cause of fibrodysplasia ossificans progressiva was identified, and definitive genetic testing for fibrodysplasia ossificans progressiva is now available before the appearance of heterotopic ossification.

METHODS

We recently evaluated 7 children for diagnosis of fibrodysplasia ossificans progressiva before the onset of heterotopic ossification. A medical history, physical examination, and skeletal survey were obtained on all of the patients, as well as clinical genetic testing for the canonical fibrodysplasia ossificans progressiva mutation.

RESULTS

All 7 of the children (4 girls and 3 boys; ages 3 months to 6 years) had congenital malformations of the great toes, but none had radiographic evidence of heterotopic ossification at the time of evaluation. Five of the 7 children had soft tissue lesions of the neck and back, suggestive of early fibrodysplasia ossificans progressiva flare-ups, 3 of whom had undergone invasive diagnostic procedures that exacerbated their condition. Two children had no history or signs of soft tissue swelling or flare-ups. DNA sequence analysis found that all 7 of the children had the recurrent fibrodysplasia ossificans progressiva missense mutation, a single nucleotide substitution (c.617G>A) at codon 206 in the glycine-serine activation domain of activin receptor IA, a bone morphogenetic protein type 1 receptor.

CONCLUSION

Clinical suspicion of fibrodysplasia ossificans progressiva early in life on the basis of malformed great toes can lead to early clinical diagnosis, confirmatory diagnostic genetic testing, and the avoidance of additional harmful diagnostic and treatment procedures. This is the first report of genetic confirmation of fibrodysplasia ossificans progressiva before the appearance of heterotopic ossification. Pediatricians should be aware of the early diagnostic features of fibrodysplasia ossificans progressiva, even before the appearance of heterotopic ossification. This awareness should prompt early genetic consultation and testing and the institution of assiduous precautions to prevent iatrogenic harm.

An unusual case of rapidly progressive contractures: Case report and brief review

An 8-year-old boy, diagnosed as cervical dystonia, was referred to our tertiary center. After a trivial trauma he had developed painful lumps in the axial region, which was followed by restricted movements of neck, shoulder, and abdominal muscles over 4 months. He had kyphoscoliosis, torticollis, rigid abdomen, and multiple muscle contractures. He also had short great toes. A detailed skeletal survey showed calcification in the soft tissues surrounding the shoulder anterior chest wall, thorax, and paraspinal muscles; there was also beaking of vertebrae, which was confirmed by CT thorax. This report showcases the diagnostic challenge posed by myositis ossificans progressiva, which can rarely cause rapidly progressing muscle contractures. A brief review of literature is also presented.

Proximal tibial osteochondromas in patients with fibrodysplasia ossificans progressiva

BACKGROUND

Fibrodysplasia ossificans progressiva is a rare autosomal dominant disorder characterized by congenital malformation of the great toes and by progressive heterotopic ossification of skeletal muscle and soft connective tissues. The disorder is caused by a recurrent missense mutation in the glycine-serine activation domain of activin A receptor type I, a bone morphogenetic protein (BMP) type-I receptor, in all classically affected individuals. Osteochondromas of the proximal part of the tibia are benign osteochondral neoplasms or orthotopic lesions of skeletal remodeling associated with dysregulated BMP signaling and have been considered an atypical feature of fibrodysplasia ossificans progressiva, but they may be underdiagnosed because of their often asymptomatic nature. The purpose of the present study was to determine the prevalence and characteristics of proximal tibial osteochondromas in individuals who have fibrodysplasia ossificans progressiva.

METHODS

Over a period of thirty months, we evaluated all patients with new and established fibrodysplasia ossificans progressiva for the presence of proximal tibial osteochondromas on the basis of medical history, physical examination, and radiographic studies. We quantified the prevalence of osteochondromas and characterized the types of osteochondromas to identify relevant trends.

RESULTS

Ninety-six patients (including fifty-two female patients and forty-four male patients) with fibrodysplasia ossificans progressiva were evaluated on the basis of a history and physical examination. Plain radiographs were available for sixty-seven patients. Ninety percent of all patients had osteochondroma of the proximal part of the tibia. These lesions usually were asymptomatic, most commonly were bilateral, and typically were located at the pes anserinus. Seventy-five percent of the lesions were pedunculated, and 25% were sessile.

CONCLUSIONS

Proximal tibial osteochondromas are a common phenotypic feature of fibrodysplasia ossificans progressiva, a finding that expands the recognized consequences of recurrent activating mutations in activin A receptor type I to include not only congenital skeletal malformations and heterotopic skeletogenesis but also benign osteochondral neoplasms or orthotopic lesions of skeletal modeling. The present study provides insight into the genetic basis of osteochondroma formation in patients with fibrodysplasia ossificans progressiva and possibly into that of more common conditions in which these lesions occur.

Lumbar puncture and surgical intervention in a child with undiagnosed fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare, autosomal dominant disorder characterized by congenital malformation of the great toes and episodes of soft tissue swelling that lead to progressive heterotopic ossification. The genetic cause of FOP was recently discovered to be a recurrent missense activating mutation in the activin A type I receptor, a bone morphogenetic protein type I receptor in all classically affected individuals worldwide. The authors present a child with the classic features of previously undiagnosed FOP who developed a paraspinal soft-tissue mass after a lumbar puncture for a fever workup. Excision of the mass resulted in a massive inflammatory response leading to progression of heterotopic ossification. Awareness of the classic clinical features of FOP prior to the appearance of heterotopic ossification can prompt early clinical diagnosis and confirmation through genetic testing, thus avoiding interventions that lead to irreversible iatrogenic harm.

When one skeleton is enough: approaches and strategies for the treatment of fibrodysplasia ossificans progressiva (FOP)

A heterozygous missense mutation in activin receptor IA/activin-like kinase-2 (ACVR1/ALK2), a bone morphogenetic protein (BMP) type I receptor, is responsible for fibrodysplasia ossificans progressiva (FOP), the most catastrophic disorder of skeletal metamorphosis in humans. The discovery of the FOP gene establishes a crucial milestone in understanding FOP, reveals a highly conserved target in the BMP signaling pathway for drug development and specifically stimulates therapeutic approaches for the development of inhibitors for ACVR1/ALK2 signaling. Effective therapies for FOP, and possibly for more common conditions of heterotopic ossification, will be based on interventions that selectively block promiscuous ACVR1/ALK2 signaling, and/or themolecular triggers, responding cells and tissue microenvironments that facilitate aberrant skeletal metamorphosis in a permissive genetic background of increased BMP pathway activity.

Skeletal metamorphosis in fibrodysplasia ossificans progressiva (FOP)

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.

Functional modeling of the ACVR1 (R206H) mutation in FOP

Individuals with fibrodysplasia ossificans progressiva are born with malformations of the great toes and develop a heterotopic skeleton during childhood because of an identical heterozygous mutation in the glycine-serine activation domain of ACVR1, a bone morphogenetic protein type I receptor. Substitution of adenine for guanine at nucleotide 617 replaces an evolutionarily conserved arginine with histidine at residue 206 of ACVR1 in all classically affected individuals, making this one of the most highly conserved disease-causing mutations in the human genome. To better understand the molecular constraints and physiological implications of this mutation, we performed in silico modeling of wild-type and mutant ACVR1. In both the wild-type ACVR1 model and template crystal structures (TbetaRI), the conserved arginine appears to form a salt bridge with an invariant aspartate residue. Although lysine, a conservative substitution in BMPRIA and BMPRIB, can be readily accommodated, histidine at residue 206 (like in fibrodysplasia ossificans progressiva) would participate in a salt bridge with the aspartate only at decreased intracellular pH and with extensive structural rearrangement. Protein modeling predicts that substitution with histidine, and only histidine, creates a pH-sensitive switch within the activation domain of the receptor that leads to ligand-independent activation of ACVR1 in fibrodysplasia ossificans progressiva.

Diagnostic features of fibrodysplasia (myositis) ossificans progressiva on bone scan

Fibrodysplasia ossificans progressiva (FOP) is a rare, autosomal dominant disorder of connective tissue that leads to progressive, disabling heterotopic ossification in characteristic anatomic patterns. It is accompanied by pathognomonic congenital malformation of the great toes (or thumbs) - microdactyly. There is a high occurrence of diagnostic errors in FOP, leading to inappropriate interventions that may result in significant harm to patients. Scintigraphic demonstration of heterotopic ossifications in connective tissue at characteristic locations, in combination with pathognomonic microdactyly of the great toes (or thumbs), is highly specific. The case presented here is aimed at increasing familiarity with those typical diagnostic features, especially on bone scintigraphy.