Fibrodysplasia ossificans progressiva: a clue from the fly?

Limb swelling in patients who have fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva is a rare heritable disorder of connective tissue characterized by progressive heterotopic ossification of soft tissues and by congenital malformation of the great toes. Limb swelling has also been noted, yet little is known about this complication of fibrodysplasia ossificans progressiva. To determine the prevalence of limb swelling in this condition, the authors reviewed detailed medical records on 74 patients (25 males, 49 females; age range, 1-49 years) who had a documented history of fibrodysplasia ossificans progressiva. The study population included more than 90% of all patients known to have fibrodysplasia ossificans progressiva in the United States. Acute swelling of the limbs occurred in association with flareups of the condition in nearly all cases. Acute swelling in the upper limbs was focal and nodular in contrast to acute swelling in the lower limbs, which was more diffuse. Acute swelling in the upper limbs occurred in all 74 patients whereas acute swelling in the lower limbs occurred in 47 of the 74 patients (64%). Two of the 74 patients who had acute swelling in the lower limbs (4%) had a documented episode of deep vein thrombophlebitis. Chronic swelling in the upper limbs occurred in 9 of the 74 patients (12%) and was not seen before the age of 12 years. Chronic swelling in the lower limbs occurred in 36 of the 74 patients (49%) and was not seen before the age of 9 years. The intense angiogenesis and edema seen on histopathologic evaluation of preosseous fibrodysplasia ossificans progressiva lesions may play a role in the pathogenesis of the limb swelling. The data show an age related prevalence of limb swelling in fibrodysplasia ossificans progressiva and suggest a model for understanding the complex pathways leading to limb swelling in this disorder.

Overexpression of an osteogenic morphogen in fibrodysplasia ossificans progressiva

BACKGROUND

Fibrodysplasia ossificans progressiva is a heritable disorder of connective tissue characterized by congenital malformation of the great toes and postnatal formation of ectopic bone. Although the disorder was first described more than 300 years ago, the genetic defect and pathophysiology remain unknown. Bone morphogenetic proteins are potent bone-inducing morphogens that participate in the developmental organization of the skeleton, and increased production of one or more of these proteins has been proposed as the cause of fibrodysplasia ossificans progressiva.

METHODS

We studied lymphoblastoid cell lines established from peripheral-blood mononuclear cells of patients with fibrodysplasia ossificans progressiva and fibroblast-like cell lines derived from lesional and nonlesional tissue. We used Northern blot analysis and ribonuclease protection assays to measure the expression of messenger RNA (mRNA) of bone morphogenetic proteins 1 to 7 and immunohistochemical analysis to examine protein expression.

RESULTS

Among the bone morphogenetic proteins and mRNAs examined, only bone morphogenetic protein 4 and its mRNA were present in increased levels in cells derived from an early fibroproliferative lesion in a patient with fibrodysplasia ossificans progressiva. Bone morphogenetic protein 4 mRNA was expressed in lymphoblastoid cell lines from 26 of 32 patients with fibrodysplasia ossificans progressiva but from only 1 of 12 normal subjects (P<0.001). Bone morphogenetic protein 4 and its mRNA were detected in the lymphoblastoid cell lines from a man with fibrodysplasia ossificans progressiva and his three affected children (two girls and a boy), but not from the children's unaffected mother. No other bone morphogenetic proteins were detected.

CONCLUSIONS

Overexpression of a potent bone-inducing morphogen (bone morphogenetic protein 4) in lymphocytes is associated with the disabling ectopic osteogenesis of fibrodysplasia ossificans progressiva.

Bone morphogenetic proteins and C-FOS: early signals in endochondral bone formation

The earliest events in endochondral ossification, whether in the formation of the skeleton during embryogenesis or in the regeneration of a bone during fracture healing, involve the establishment of a tissue-specific plan of gene expression arising from pluripotent mesenchymal cells. Recent data from studies of vertebrate limb bud development implicate gradients of diffusable morphogens that specify complex patterns of position-specific gene expression. Diffusable signaling molecules involved at the earliest stages of tissue development include fibroblast growth factors, platelet derived growth factors, bone morphogenetic proteins, transforming growth factor beta, and sonic hedgehog; there are undoubtedly others. An equally elaborate array of trans-membrane receptors in the tyrosine kinase and serine-threonine kinase signaling pathways are responsible for transducing these morphogenetic signals and for establishing boundaries of gene expression. Nuclear signals for transcriptional activation, such as the fos-jun proto-oncogene family and homeobox genes, are also involved in the specification and modification of morphogenetic plans. While much has been learned recently about the presence and interaction of these growth factors and transcription factors in the development of the vertebrate limb bud, very little is known about their presence and interaction in the earliest stages of post-natal bone formation at a fracture site or in heterotopic osteogenesis. Fibrodysplasia ossificans progressiva (FOP) a rare genetic disorder of heterotopic ossification, provides a unique opportunity to study the role of these morphogens and proto-oncogenes in the earliest events of endochondral bone formation.

Submandibular Swelling in Patients with Fibrodysplasia Ossificans Progressiva

Fibrodysplasia ossifcans progressiva (FOP) is a rare genetic disorder characterized by congenital malformation of the great toes and by progressive heterotopic ossification of soft tissues. Although ankylosis of the temporomandibular joint occurs commonly in the late stages of the disease, only one well-documented case of submandibular heterotopic ossification in a patient who had FOP exists. Twelve (11%) of our 107 patients who have FOP had submandibular heterotopic ossification that was mistaken initially in seven of the patients for mumps, angioneurotic edema, abscess, mononucleosis, or neoplasm. Two male patients and 10 female patients ranging in age from 6 to 47 years (mean, 21 years) were studied. Ten patients survived following assiduous precautionary measures. One patient who required emergency tracheostomy and ventilatory support also survived. Another patient died of inanition from chronic swallowing difficulty. An effective treatment program includes early identification of the submandibular flare-up, nutritional support, and glucocorticoid therapy. Submandibular swelling in patients who have FOP can be a medical emergency and requires intensive precautionary measures to avoid catastrophic clinical deterioration. These measures include avoidance of lesional manipulation, airway monitoring, and aspiration precautions. Submandibular swelling should be recognized as a variable feature of FOP.

Fibrodysplasia ossificans progressiva in two half-sisters: evidence for maternal mosaicism

Fibrodysplasia ossificans progressiva (FOP) is a rare autosomal dominant disorder of connective tissue characterized by congenital malformation of the great toes and by progressive heterotopic ossification of the soft tissues in specific anatomic and temporal patterns. We observed classic findings of FOP in 2 Native American half-sisters with the same unaffected mother and different unaffected fathers. This is the first report of FOP in sibs from different pregnancies with unaffected parents. The findings in this family indicate the possibility of maternal gonadal mosaicism in FOP and provide important new data for genetic counseling in this disease.

Severe restriction in jaw movement after routine injection of local anesthetic in patients who have fibrodysplasia ossificans progressiva

OBJECTIVE

To determine the relationship of dental procedures to immediate ossification and ankylosis of the jaw in patients who have fibrodysplasia ossificans progressiva.

STUDY DESIGN

A mail survey was conducted of the 60 patient-members of the International Fibrodysplasia Ossificans Progressiva Association. All 41 patients (18 males, 23 females) who responded were examined. Instantaneous exact hazard rates for ossification of the jaw were calculated by the Weibull model.

RESULTS

Thirty-six patients had dental procedures performed. Twenty-one (58%) patients had received an injection of local anesthetic. Five (24%) patients had an immediate flare-up of fibrodysplasia ossificans progressiva with ossification and permanent ankylosis of the jaw (expected occurrence, 0.031; p < 0.0001). None of the 12 patients who had comparable dental work without injections developed heterotopic ossification (expected occurrence, 0.019; not significant).

CONCLUSION

Injections of local anesthetic during dental procedures pose serious and immediate risk for inciting heterotopic ossification and ankylosis of the jaw in patients who have fibrodysplasia ossificans progressiva and should be assiduously avoided.

Linkage between stature and a region on chromosome 20 and analysis of a candidate gene, bone morphogenetic protein 2

Sib-pair linkage analysis of the quantitative trait, structure, in over 500 Pima Indians indicates that a genetic determinant of governing stature is located on chromosome 20. Analysis of 10 short tandem repeat polymorphisms localized this linkage to a 3.2cM region that includes D20S98 and D20S66. Using all possible sib-pair combinations, linkage was detected to both stature (P = 0.0001) and to leg length (P = 0.001), but not to sitting height. Single-strand conformational polymorphism analysis of exon 3 of the bone morphogenetic protein 2 (BMP2) gene, a candidate gene in this region, in genomic DNA of 20 of the tallest and 20 of the shortest individuals did not show any consistent differences associated with leg length or height. Sequence analysis of the region encoding the mature protein revealed a single nucleotide substitution, a T to G transversion, not detected by single-strand conformational polymorphism (SSCP) analysis. This transversion results in a conservative amino acid substitution of glycine for valine at codon 80 of BMP2. The frequency of this allele was 0.23 in the sample. No significant differences in height were noted in persons carrying either allele. This indicates that this structural alteration is the mature BMP2 protein does not contribute to the differences in stature observed in the Pima Indians, nor is this structural change in the mature protein likely to be responsible for the linkage observed with stature on chromosome 20.

Fibrodysplasia ossificans progressiva: still turning into wood after 300 years?

Fibrodysplasia ossificans progressiva (FOP), a rare autosomal dominant disorder, is characterized by symmetrical congenital skeletal abnormalities and progressive heterotopic ossification of the connective tissues. At present, more than 300 years after the first report by Patin in 1648 in which he described the woman who "turned to wood", its pathogenesis remains largely unknown and its therapy is limited to symptom-modifying trials. However, significant progress has been recently made and new data on the molecular organization and regulation of normal and disordered bone induction are likely to lead to a more specific therapy. FOP is believed to be a genetic disorder characterized by a disturbed expression of the endochondral osteogenesis programme, and the remarkable "clues from the fly" reported by Kaplan et al. [8] in 1990 suggest a gain-of-function mutation in the genetic regulation of bone morphogenetic proteins.

Permanent heterotopic ossification at the injection site after diphtheria-tetanus-pertussis immunizations in children who have fibrodysplasia ossificans progressiva

In patients who have fibrodysplasia ossificans progressiva, routine childhood diphtheria-tetanus-pertussis immunizations administered by intramuscular injection caused a significant risk of permanent heterotopic ossification at the site of injection (p < 10(-8)), whereas measles-mumps-rubella immunizations administered by subcutaneous injection posed no significant risk. Intramuscular injections should be avoided, if possible, once a diagnosis of fibrodysplasia ossificans progressiva has been established.

[Myositis ossificans progressiva]

BACKGROUND

Myositis ossificans progressiva is a rare progressive disease of connective tissue with a poor prognosis.

CASE REPORT

A 16 year-old girl suffered from lameness of her right leg associated with inguinal swelling. Progressive aggravation of pain with extension of swelling to the posterior part of her thigh required an X-ray examination which showed hip dysplasia and calcifications around the hip. Angiography was normal; a diagnosis of hematoma was suggested by scannography and bone scintigraphy, but biopsy showed features of nodular fasciitis. The association of progressive ectopic ossification to malformation of the big toe led to diagnosis of myositis ossificans progressiva.

CONCLUSIONS

Congenital malformations, most commonly of big toes and thumbs, are important for distinguishing myositis ossificans progressiva from other diseases of muscle.

Fibrodysplasia (myositis) ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare hereditary connective tissue disorder. Patients with FOP develop progressive ossification of muscle and connective tissue associated with pain and disability. Onset is typically in childhood, and congenital anomalies of the feet are an early sign of this condition. Pain and stiffness of the spine or an inflammatory mass are common presenting features of FOP. Involvement of the spine often leads to complete fusion mimicking ankylosing spondylitis. Studies of twins and families suggest that FOP is a genetically inherited autosomal dominant trait with complete penetrance but variable expressivity. While radionuclide imaging and computed tomography are very sensitive for new bone formation and greatly assist the diagnosis of FOP, unfortunately, effective therapy is unavailable. We present twins with FOP and review the clinical, radiographic, and genetic manifestations of this disorder.

Heterotopic Ossification: Two Rare Forms and What They Can Teach Us

Heterotopic ossification is characterized by the formation of normal bone at ectopic soft-tissue locations. Regardless of the etiology of heterotopic ossification, requisite pathogenetic conditions include an inductive signal capable of stimulating morphogenesis, a population of inducible osteoprogenitor cells, and a heterotopic environment conducive to osteogenesis. Two rare heritable and developmental forms of heterotopic ossification, fibrodysplasia ossificans progressiva and progressive osseous heteroplasia, provide valuable clinical and pathogenetic insights into heterotopic ossification in humans. A fundamental understanding of the developmental and molecular pathology of these disorders may lead to more effective strategies for preventing and treating heterotopic ossification in humans.

Genetic transmission of fibrodysplasia ossificans progressiva. Report of a family

Fibrodysplasia ossificans progressiva is a rare connective-tissue disorder characterized by congenital malformation of the great toes and by progressive heterotopic ossification of the tendons, ligaments, fasciae, and skeletal muscles. We document the genetic transmission of fibrodysplasia ossificans progressiva from a sporadically affected father to each of his three children: two daughters and a son. Previous consideration of a genetic etiology was based on the fact that the disease has been reported in several sets of monozygotic twins, that an increased paternal age has been associated with sporadic occurrences of the disorder, and that there have been several reports of genetic transmission in the remote past. Although an autosomal-dominant genetic transmission has long been suspected, the findings in the family reported on here provide confirmation for such inheritance and a basis for the diagnosis and counseling of patients who have this disease.

The natural history of heterotopic ossification in patients who have fibrodysplasia ossificans progressiva. A study of forty-four patients

Forty-four patients who had fibrodysplasia ossificans progressiva responded by mail to a questionnaire regarding the age at the onset of heterotopic ossification at fifteen commonly involved anatomical sites. The average age of the patients when they responded to the questionnaire was twenty-seven years (range, three to sixty-nine years). The average age at the onset of ossification was five years (range, birth to twenty-five years). The most common sites of early heterotopic ossification were the neck, spine, and shoulder girdle. Thirty-five (80 per cent) of the patients had had some restrictive heterotopic ossification by the age of seven years. By the age of fifteen years, forty-two (more than 95 per cent) of the patients had severely restricted mobility of the upper limbs. In these patients, heterotopic ossification proceeded in a direction that was axial to appendicular, cranial to caudad, and proximal to distal; this pattern appeared typical for fibrodysplasia ossificans progressiva.

The histopathology of fibrodysplasia ossificans progressiva. An endochondral process

In order to better characterize the biological features of fibrodysplasia ossificans progressiva, we reviewed the histopathological specimens from eleven patients (twelve biopsies) who had a confirmed diagnosis of the disease. All of the biopsies had been performed in children, to exclude the diagnosis of a malignant lesion. In no instance was the diagnosis of fibrodysplasia ossificans progressiva considered before the biopsy. The results of a lesional biopsy in all eleven patients revealed normal endochondral osteogenesis at heterotopic sites. The results of biopsy of an early lesion in six children were misinterpreted as revealing a diagnosis of fibromatosis or sarcoma before the roentgenographic appearance of ossification. Immunohistochemical studies of sections of the earliest lesion demonstrated S-100 antigen positivity before the histological appearance of differentiated osteochondral tissue. The presence of congenital malformation of the great toes and of postnatal heterotopic endochondral osteogenesis strongly suggests that fibrodysplasia ossificans progressiva is a disorder of defective induction of endochondral osteogenesis. This study established the predominant histopathological findings associated with fibrodysplasia ossificans progressiva and can serve as a basis for postulation of a candidate gene in the pathogenesis of the disorder. A lesional biopsy is not needed to make the diagnosis; biopsy uniformly exacerbates the condition and should be avoided.

A bone morphogenetic protein subfamily: chromosomal localization of human genes for BMP5, BMP6, and BMP7

Bone morphogenetic proteins (BMPs) were originally identified by the ability of a demineralized bone extract to induce endochondral osteogenesis in vivo. Seven BMP cDNAs (BMP1 through BMP7) have been recovered through molecular cloning. Recombinant protein products from six of these clones (BMP2 through BMP7) are members of the transforming growth factor beta (TGF-beta) superfamily of regulatory molecules. Based upon a high degree of amino acid sequence homology, BMP5, BMP6, and BMP7 constitute a subfamily within the BMPs. Using human-rodent somatic cell hybrid lines and cDNA probes, we mapped the three members of this subfamily of genes to the human chromosomes. BMP5 and BMP6 are syntenic on human chromosome 6, while BMP7 is syntenic with previously localized BMP2 on human chromosome 20. This analysis reveals that BMP6 maps to a conserved region between the mouse and human genomes. Sequence analysis suggests that the Drosophila 60A gene is the dipteran homolog of this BMP subfamily and may provide clues to the physiologic functions of the products of these genes in human biology.

The role of morphogens in endochondral ossification

The formation of bone occurs normally by one of two developmental processes: intramembranous or endochondral ossification. Endochondral ossification occurs in the morphogenesis of the limb buds and growth plates, and in the regeneration of bone following injury (fracture callus). Two classes of diffusible morphogen-like molecules (MLMs) involved in limb development are the bone morphogenetic proteins (BMPs) and retinoic acid (RA). These MLMs are associated, respectively, with the apical ectodermal ridge (AER) and the zone of polarizing activity (ZPA) of the primitive limb bud. They function as potent regulators of pattern formation and are involved in tissue proliferation and differentiation. The presence of endochondral ossification in fracture callus suggests a role for MLMs in that process as well. To date, virtually nothing is known about the role of morphogens in the regeneration of bone (fracture healing). In this article, we review the current knowledge of MLMs in bone formation and propose a theory on their role in fracture healing. We hypothesize that MLMs involved in fracture healing may also express spatial and temporal information. A more complete understanding of the role of morphogens in both limb development and fracture healing is of major importance to practicing orthopedists and their patients.

The Drosophila dorsal-ventral patterning gene tolloid is related to human bone morphogenetic protein 1

Mutations in the Drosophila tolloid (tld) gene lead to a partial transformation of dorsal ectoderm into ventral ectoderm. The null phenotype of tld is similar to, but less severe than decapentaplegic (dpp), a TGF-beta family member required for the formation of all dorsal structures. We have cloned the tld locus by P element tagging. At the blastoderm stage, tld RNA is expressed dorsally, similar to that described for dpp. Analysis of a tld cDNA reveals three sequence motifs: an N terminal region of similarity to a metalloprotease, two EGF-like repeats, and five copies of a repeat found in human complement proteins C1r and C1s. tld sequence is 41% identical to human bone morphogenetic protein 1 (BMP-1); the closest members to dpp within the TGF-beta superfamily are BMP-2 and BMP-4, two other bone morphogenetic proteins. These findings suggest that these genes are members of a signal generating pathway that has been conserved between insects and mammals.

Bone morphogenetic protein: chromosomal localization of human genes for BMP1, BMP2A, and BMP3

Bone morphogenetic protein (BMP) induces endochondral bone formation in vivo. The human genes have been cloned for a group of proteins containing BMP activity (BMP1, BMP2A, and BMP3). Two of the proteins are members of the transforming growth factor-beta supergene family (BMP2A and BMP3), while BMP1 is a novel regulatory protein. Using somatic cell hybrid lines, cDNA probes were used to map BMP1 to chromosome 8, BMP2A to chromosome 20, and BMP3 to the p14-q21 region of chromosome 4. This analysis reveals that the BMP2A and BMP3 genes map to conserved regions between mouse and human, while the BMP1 gene does not. The locations of the BMP genes were found to overlap with the loci for several disorders of cartilage and bone formation.