Bone morphogenetic protein 2/4 in early fibromatous lesions of fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disorder characterized by congenital malformation of the great toes and progressive heterotopic ossification in distinct anatomic patterns. Early preosseous lesions in FOP are clinically and histologically indistinguishable from the lesions of aggressive juvenile fibromatosis (AJF). Although the genetic defect in FOP is unknown, bone morphogenetic proteins (BMPs) 2 and 4 are plausible candidates genes. To determine if there is a difference in BMP 2/4 expression in the early fibromatous lesions of the two conditions, we performed immunohistochemical studies with a monoclonal antibody to BMP 2/4 on the earliest detectable fibromatous lesions of FOP and compared them with histologically identical lesions resected from children who had AJF. Fibromatous cells from the early FOP lesions exhibited immunostaining for BMP 2/4, whereas histologically indistinguishable fibromatous cells from AJF lesions showed no evidence of BMP 2/4 immunostaining. It is incumbent on all physicians who treat patients with suspected fibromatosis to examine the toes to rule out FOP and to avoid unnecessary diagnostic biopsies because surgical trauma induces further bone formation in patients who have FOP. However, if diagnostic confusion still exists and a biopsy is performed, immunostaining with BMP 2/4 antibody may resolve the diagnostic dilemma between FOP and AJF before the appearance of heterotopic ossification is observed in the FOP lesions. Our data suggest that the BMP 2/4 subfamily of secreted proteins may be involved in the pathogenesis of the FOP lesions.

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.

Fibrodysplasia ossificans progressiva: report of a case with guidelines for pediatric dental and anesthetic management

Fibrodysplasia ossificans progressiva (FOP) is a rare heritable disorder of progressive heterotopic ossification leading to joint ankylosis throughout the body. Permanent ankylosis of the jaw may be precipitated by minimal soft tissue trauma, a potentially devastating complication following routine dental care during childhood. Assiduous precautions are necessary in administering dental care to children who have FOP as exemplified in this case report. Routine dental prophylaxis is also necessary in order to minimize the need for invasive procedures.

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.

Skeletal response to immobilization in Paget's disease of bone: a case report

The authors discuss a case of Paget's disease of the forearm in which the Pagetic radius and non-Pagetic ulna responded differently to immobilization. The high turnover state of Pagetic bone is more sensitive to physical unloading than normal bone, and thus more rapidly develops osteopenia of immobilization. The different responses to immobilization between Pagetic bone and site controlled normal bone illustrate how physical and metabolic factors interact at a skeletal site to regulate bone remodeling and bone mass.

Skin and bones

Through the examples above, we can begin to see how rare diseases may shed light not only on more common conditions but also on each other. Disorders such as FOP, POH, MAS, and AHO provide a fertile molecular neighborhood for investigating a disease such as POH. Will POH be linked to the G proteins, c-fos, the BMPs, the BMP receptors, or perhaps an as yet undiscovered gene? For the moment, there are few answers, but there are at least some tantalizing questions to ponder and investigate. We all look forward to the day when our knowledge of, and treatment for, diseases like POH will be more than just skin and bones.

Submandibular swelling in patients with fibrodysplasia ossificans progressiva

Fibrodysplasia ossifcans progressive (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 40 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.

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.

Tutorial. Molecular biology for the clinician. Part II. Tools of molecular biology

This is the second of a series of tutorials on molecular biology for the clinician. Part I introduced general principles of nucleic acid and gene structure. This tutorial will build on those general principles and describe some of the commonly used techniques employed in research and diagnosis to examine genes and gene function. The tools of molecular biology include recombinant DNA techniques that have revolutionized the study of DNA and genetic information. Recombinant DNA technology allows the isolation of specific regions of chromosomal DNA and the recovery of unlimited quantities of that DNA for analyses, including determination of the nucleotide sequence of genes, examination of the mechanisms of gene regulation, and the identification of gene products (RNA and protein).

Severe osteoporosis in men

OBJECTIVE

To evaluate men with severe osteoporosis for pathogenetic factors and to review the reported features of primary osteoporosis in men.

DESIGN

Case series and clinical review.

PATIENTS

47 men consecutively referred to a metabolic bone center because of atraumatic (or minimally traumatic) fractures (91%) or radiographic osteopenia (9%).

MEASUREMENTS

Clinical assessment, radiographs, chemical analyses of serum and urine, hormone assays, skeletal densitometry, and histomorphometry of iliac crest biopsy specimens.

RESULTS

27 of the 47 men (57%) had vertebral fractures, and 16 (34%) had appendicular fractures. Causal factors identified in 30 men (64%) included glucocorticosteroid treatment (8 men); hypogonadism (7 men); excessive alcohol consumption (7 men); and anticonvulsant use, osteomalacia, severe hyperthyroidism, or bone marrow neoplasia (8 men). Seventeen men (36%) had no medical conditions or known risk factors associated with bone disease. Spinal mineral density was well below the mean value for healthy young men in 94% of the patients with primary osteoporosis tested. Examination of biopsy specimens from 13 of 17 men with primary osteoporosis showed reduced trabecular bone volumes, normal bone formation rates, and slightly increased resorption surfaces. Fasting hypercalciuria was seen in some men (41%). In the primary osteoporosis group, eight men were followed serially (range of follow-up, 6 months to 9 years) while they were receiving a nonpharmacologic regimen (diet and activity); the mean axial bone mineral density of these men increased slightly.

CONCLUSIONS

A thorough evaluation for identifiable causes of severe osteoporosis in men is warranted because definable pathogenetic factors are seen in many cases. A few men with severe osteoporosis have primary or idiopathic osteoporosis. Primary osteoporosis in men is probably caused by many factors because heterogeneous clinical, laboratory, and histologic features were seen in our series and in those of others. Further studies of primary osteoporosis are needed to define the course of the disease, to identify pathogenetic mechanisms, and to develop therapeutic interventions.

Topographic changes in a heterochromatic chromosome block in humans (15P) during formation of the nucleolus

Fluorescence in situ hybridization and multispectral confocal laser scanning microscopy revealed a highly dynamic nucleolar-associated chromosome 15 satellite III heterochromatin cluster in humans. This nucleolar-associated DNA was highly decondensed at the metaphase plate compared with its topography at interphase and appeared to act as a centre for the post-mitotic reorganization of the nucleolus. Our data showed unexpected trans-mitotic changes in the topography of this nucleolar-associated satellite III DNA that suggest that this locus-specific heterochromatin superstructure may be involved in nucleolar organization.

Progressive osseous heteroplasia in male patients. Two new case reports

Progressive osseous heteroplasia is a rare developmental disorder of mesenchymal differentiation characterized by cutaneous osteomas in infancy and by progressive heterotopic intramembranous ossification of skin and deep connective tissue. To date, typical features of the disorder have been reported only in 8 female patients. This report documents progressive osseous heteroplasia in 2 boys and has important implications for the clinical detection and pathogenetic understanding of this rare disorder.

Diabetes-like renal glomerular disease in Fanconi-Bickel syndrome

The Fanconi-Bickel syndrome is a rare inherited disorder of metabolism characterized by hepatic glyconeogenesis, galactose intolerance, renal Fanconi syndrome with nephromegaly, and glycogen accumulation in proximal renal tubular cells. An 8-year-old patient with this disease and severe rickets due to medically resistant hypophosphatemia was found to have the previously unrecognized complication of renal glomerular hyperfiltration, microalbuminuria, and diffuse glomerular mesangial expansion. Similar to patients with glucose-6-phosphatase deficiency, the glomerular disease in this patient resembles incipient diabetic nephropathy. The Fanconi syndrome may be due to the defective transport of glucose at the proximal tubular basolateral membrane, which results in accumulation of glucose and secondarily glycogen within tubular cells. Since the metabolic defect, as evidenced by glycogen accumulation, selectively involves proximal renal tubular cells in the kidney of patients with Fanconi-Bickel syndrome and glucose-6-phosphatase deficiency, the abnormalities in renal glomerular hemodynamics and mesangial construct in these rare diseases are likely due to renal tubular factors, if the mechanism originates in the kidney. A delineation of these phenomena may further our understanding of the pathogenesis of diabetic nephropathy.

Mild expression of fibrodysplasia ossificans progressiva: a report of 3 cases

We describe 3 unusually mild cases of fibrodysplasia ossificans progressiva (FOP) in an 80-year-old man, a 44-year-old woman, and a 17-year-old woman. The man, whose daughter had classic features of FOP, lacked malformation of the great toes and experienced unusually slow progression of the disease. Both women displayed late onset heterotopic ossification. The older women displayed an unusually slow progression of the disease. All 3 patients remained ambulatory at the time of examination. Recognition of a mild form of FOP will influence diagnosis, counselling, and research in this rare condition.

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.

Severe symptomatic osteopenia in a man with pigmented micronodular adrenal hyperplasia

The authors describe the unusual case of a 52-year-old man with Cushing's syndrome caused by bilateral pigmented micronodular adrenal hyperplasia. The only features of hypercortisolism were hypertension and severe symptomatic osteopenia with vertebral, rib, and scapular fractures. Four years after bilateral adrenalectomy, the bone density had increased slightly, but the patient remained osteopenic and continued to have vertebral compression fractures. This case report emphasizes the importance of an indepth search for secondary causes of osteoporosis, including evaluation of adrenal function in patients who have unexplained osteoporosis. Early diagnosis and treatment is imperative to prevent severe bone loss and associated skeletal morbidity.

BMP-1 sublocalization on human chromosome 8. Molecular anatomy and orthopaedic implications

Bone morphogenetic proteins are capable of inducing mesenchymal tissue to form mature bone. Bone morphogenetic protein 1 (BMP-1) has a structure unique from the other bone morphogenetic proteins and may be involved in activation of other bone morphogenetic proteins. Localization of the human BMP-1 gene to chromosome 8 led to its consideration as a candidate gene for Langer-Giedion syndrome. Individuals with Langer-Giedion syndrome (also known as trichorhinophalangeal syndrome Type II) exhibit several skeletal abnormalities, including multiple exostoses and cone-shaped epiphyses of the hands and feet. The genetic locus responsible for this disease has been localized to the long arm of human chromosome 8 at 8q24.1. Somatic-cell hybrid and molecular biology techniques were used to sublocalize the BMP-1 gene to the short arm of chromosome 8 within the 8p22-cen region. Although this locus falls outside the Langer-Giedion syndrome region, and therefore excludes BMP-1 as a candidate gene for this disorder, BMP-1 gene sublocalization establishes a chromosomal landmark for evaluating other possible disease associations with BMP-1.

Traumatic fractures of heterotopic bone in patients who have fibrodysplasia ossificans progressiva. A report of 2 cases

Fibrodysplasia ossificans progressiva is an extremely rare genetic disorder characterized by the formation of a heterotopic skeleton that is histologically, biomechanically, and metabolically indistinguishable from the normotopic skeleton. Isolated cases of traumatic and pathologic fractures have been reported in the normotopic skeleton of patients who have fibrodysplasia ossificans progressiva, but to the authors' knowledge there have been no detailed reports of traumatic fractures in the heterotopic skeleton of patients who have this disease. Reported here are 2 children with fibrodysplasia ossificans progressiva who sustained traumatic fractures of heterotopic bone around the elbows. In both children, the fractures healed uneventfully with normal-appearing callus. These 2 extremely rare cases suggest that the biologic response to fractures in the heterotopic skeleton appears indistinguishable from that in the normotopic skeleton in patients who have fibrodysplasia ossificans progressiva.

Spinal deformity in patients who have fibrodysplasia ossificans progressiva

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)

Tutorial. Molecular biology for the clinician. Part I. General principles

A fundamental understanding of all biological processes requires an understanding of the molecular basis of cellular function. The discipline of molecular biology focuses on the genetic information in cells: how is the inherited information encoded within DNA and how is this information regulated and expressed so that the cells of a multicellular organism develop from a single cell to highly specialized cells in a complex and integrated organism? For the practicing clinician, an understanding of the molecular mechanisms by which a differentiated cell develops and maintains its specialized functions is critical to a more in-depth understanding of human diseases. This is the 1st of a 3 part series on molecular biology for the clinician. This article introduces general principles of nucleic acid and gene structure. The 2nd article will examine commonly used research and diagnostic techniques based on the principles of molecular biology. The 3rd part will examine the frontiers of gene therapy, a novel approach to the treatment human diseases at the molecular level.

Radiographic and scintigraphic features of modeling and remodeling in the heterotopic skeleton of patients who have fibrodysplasia ossificans progressiva

To characterize the radiographic and scintigraphic features of modeling and remodeling in the heterotopic skeleton of patients who have fibrodysplasia ossificans progressiva, radiographs from 47 patients and radionuclide bone scans from 12 of those patients, all of whom had a confirmed diagnosis of the disease, were reviewed. A wide range of normal bone modeling and remodeling features was seen in the heterotopic skeleton of all but the youngest two (age, 1 year) of the 47 patients. Characteristic features of normal bone modeling identified on radiographs of the heterotopic skeleton included: (a) the development of tubular and flat bones with mature cortical and trabecular organization; (b) the presence of well defined cortical-endosteal borders enclosing medullary canals; and (c) the presence of metaphyseal funnelization in isolated ossicles or at sites of synostoses. Characteristic features of normal bone remodeling identified on radiographs of the heterotopic skeleton included: (a) the response of heterotopic bone to weight bearing stress with osteosclerosis of use and osteopenia of disuse, and (b) the resistance of heterotopic bone to fatigue failure with the absence of pathologic fractures and stress fractures. Radionuclide bone scans in 12 patients showed that remodeling of mature heterotopic bone occurred at a rate consistent with that of mature normotopic bone. This study documents the radiographic and scintigraphic features of a heterotopic skeletal system in 47 patients who have fibrodysplasia ossificans progressiva. These data provide additional support for the hypothesis that the genetic defect leading to the formation of a heterotopic skeleton involves normal skeletal morphogenesis at heterotopic sites.

Age- and joint-specific risk of initial heterotopic ossification in patients who have fibrodysplasia ossificans progressiva

Using data from a survey of 44 patients who have fibrodysplasia ossificans progressiva, age- and joint-specific risks of new joint involvement were estimated using parametric and nonparametric statistical methods. Regions in which the risk of heterotopic ossification appears to remain constant with age include the neck, spine, shoulders, elbows, and ankles. Regions with apparently increasing risk include the jaw, wrists, hips, and knees. This analysis allows clinicians to estimate the risk of new involvement for any joint at any patient age, as well as the fraction of patients with uninvolved joints at any age. The variation of ossification risk by joint provides a clinically useful guide to the patterns of progression of the disease. Such a guide will help in planning for individual patient needs, as well as anticipating auxiliary social services and rehabilitation programs.

Paget's disease of bone: orthopedic complications

Orthopedic complications of Paget's disease are among the most common indications for treatment of Paget's disease. These complications include severe bone pain, joint pain, skeletal deformity, pathological fracture, and rarely malignant degeneration. The use of effective pharmacological modalities has transformed the treatment of Paget's disease in the past four decades. Although few patients with Paget's disease ever require surgical therapy, successful surgical management of severe orthopedic complications has improved the quality of life for many sufferers. Selected modalities with promising results include total hip replacement for intractable pagetic arthritis of the hip, proximal tibial osteotomy for painful malalignment of the knees, total knee replacement for intractable arthritis of the knee, and internal fixation for pathological fracture. Common surgical complications of joint replacement include infection, hemorrhage, heterotopic ossification, and aseptic loosening. The medical, surgical, and rehabilitation modalities available in managing primary and secondary orthopedic complications of Paget's disease provide a wide array of options that must be carefully considered in each patient.

The cluster phenomenon in patients who have multiple vertebral compression fractures

Little is known about the natural history of patients who have multiple compression fractures. During an eight-year period, eight patients who suffered relentless nonmechanical back pain after an initial compression fracture were evaluated. Radiographs and radionuclide bone scans were obtained in all eight patients and showed the temporal clustering of at least five spontaneous thoracic or lumbar vertebral compression fractures within a period of eight months. The patient database during this eight-year period included 21 patients with a similar number of fractures but without the phenomenon of temporal clustering. Age and gender distribution, premorbid activity levels, presence of secondary causes of osteopenia, dietary history, and vertebral bone density measurements were similar in both groups. Five of the eight patients with cluster fractures were on chronic glucocorticoid therapy for treatment of an underlying illness. All five patients experienced an exacerbation of their chronic illness that required an increase in the dose of their steroid medication within three months preceding the onset of the cluster fractures. No patient in the noncluster fracture control group experienced a similar exacerbation of an underlying illness or required a similar boost in their steroid medication. The temporal clustering of numerous fractures (cluster phenomenon) is a cause of transient severe disability in patients who have profound osteopenia, and may be precipitated by exacerbation of an intercurrent illness or by an associated obligate increase in glucocorticoid medication in a patient with preexisting severe osteopenia.

Osteopetrorickets. The paradox of plenty. Pathophysiology and treatment

Rickets is a common and paradoxical feature of infantile malignant osteopetrosis and results from the inability of osteoclasts to maintain a normal calcium-phosphorus balance in the extracellular fluid. Despite a markedly positive total body calcium balance, rickets arises when the serum calcium x phosphorus product is insufficient to mineralize newly formed chondroid and osteoid. In five children with malignant infantile osteopetrosis, there were clinical, radiographic, biochemical, and histologic findings of rickets. Characteristic biochemical abnormalities included hypocalcemia, hypophosphatemia, and elevated levels of serum acid phosphatase, alkaline phosphatase, c-terminal parathyroid hormone, and 1,25-dihydroxyvitamin D. The urinary calcium/creatinine ratio was markedly depressed. The serum calcium x phosphorus product was below 30 in all children at the time the rickets was diagnosed, and above 40 by the time the rickets had resolved. Baseline bone density measurements were markedly elevated in all children (> 5 standard deviation above normal) and showed even significant increases (> 7 SD) when the rickets was treated with vitamin D and calcium. The children showed marked clinical improvement, decreased lethargy, increase in mobility and activity, and stimulation of appetite, without any additional adverse hematologic or neurologic effects. The rickets was reversible in all children: in one by HLA-identical sibling bone marrow transplantation and in four by physiologic doses of vitamin D and calcium. The parathyroid and renal responses to hypocalcemia were appropriate, but glucocorticoids, used in treating the hematologic complications of the disease, may have blunted the intestinal response to maximal vitamin D stimulation. This latter blockade can be overcome by increasing dietary calcium. By liberalizing rather than by restricting calcium and phosphorus intake, hypocalcemia can be minimized, phosphorus metabolism can be improved, and rickets can be cured.

Bone densitometry observations of osteopetrosis in response to bone marrow transplantation

Spinal bone density was measured in eight patients with osteopetrosis to assess the natural history of the disease and to monitor the response to therapy. Quantitative computed tomographic scans of the lumbar vertebra were obtained in seven patients, and dual photon absorptiometric scans were obtained when the technique became available. Six children were afflicted with the infantile malignant recessive condition and two with the less severe dominant condition. In all cases, bone densitometry values ranged from four to five times higher than the mean for normal age and gender-matched controls. In four children with recessive osteopetrosis, quantitative computed tomographic and dual photon absorptiometric scans showed an excellent correlation (R = 0.93) between the methods. Quantitative computed tomographic values ranged from 597 to 730 mg/cm3 (mean = 655 mg/cm3) in children with osteopetrorickets and from 901 to 1000 mg/cm3 (mean = 980 mg/cm3) in the same children when the rickets was cured. In two children treated with bone marrow transplantation, bone densitometry values returned to normal within three years. Bone densitometry provides a safe and noninvasive method for observing the natural history and therapeutic response of the osteopetrotic syndromes.

Enchondroma in a patient with fibrodysplasia ossificans progressiva

Fibrodysplasia ossificans progressiva (FOP) is a rare heritable disorder characterized by progressive heterotopic endochondral bone formation arising in ligament, tendon, and the fibrous connective tissue of skeletal muscle. The disorder is almost invariably associated with skeletal malformations of the endochondral anlage of the feet. A 25-year-old woman with FOP had a histopathologically documented phalangeal enchondroma. This common neoplasm of cartilage and bone seems not to have been previously reported in FOP; it may represent a coincidental occurrence, but in the context of the patient's genetic disorder, an enchondroma may represent an unusual and variable expression of the disease.

Chromosomal assignment of the human gene for bone morphogenetic protein 4

Bone morphogenetic proteins (BMP) are the only known biologic factors capable of inducing endochondral ossification at an extraskeletal site. Seven members of the BMP family have been identified thus far and are involved in osteoinduction and morphogenesis. The authors established the chromosomal assignment of the gene for BMP4 on human chromosome 14 by using somatic cell hybrid panels and molecular technology. The genetic map of chromosome 14 shows that Holt-Oram Syndrome (HOS), a heritable disorder of skeletal and cardiac development, may be located also on chromosome 14. Linkage analysis studies in large families with HOS will determine if the BMP4 gene is related to HOS. In addition, analysis shows that the BMP4 gene maps to a conserved region of the mouse and human genomes. The chromosomal locus of a gene is part of human anatomy and provides a genomic landmark for studies on the pathogenesis of heritable disorders.

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.

Skeletal dysplasia in perinatal lethal osteogenesis imperfecta. A complex disorder of endochondral and intramembranous ossification

Osteogenesis imperfecta (OI) Type II is a rare heritable disorder of bone matrix that results in catastrophic congenital skeletal dysplasia. Two cases of OI Type II had symmetric rhizomelic skeletal dysplasia apparent on ultrasound at 16 and 20 weeks' gestation. Histologic and histochemical studies performed on skeletal tissue from fetal autopsies showed the following: (1) abnormal growth plate tissue characterized by failure of formation of primary bony spongiosa; (2) persistence of calcified cartilage bars in the diaphysis; (3) metaphyseal microfractures; (4) abundant cartilaginous fracture callus; (5) absence of bony callus; (6) failure of formation of intramembranous cortical diaphyseal bone; (7) angulation of long bones in portions of the metadiaphyses bordered by fracture callus; and (8) mechanical failure of the perichondral ring of LaCroix with a normal fibrous ossification groove of Ranvier. These findings suggest that skeletal dysplasia in OI Type II results from the action of muscular forces on a skeleton weakened by a complex disorder of endochondral and intramembranous ossification. The paucity of primary metaphyseal trabeculae and subperiosteal cortical bone leads to pathologic fractures of the immature fiber bone and an imperfect attempt at fracture repair. Angulation and shortening of long bones occurs between numerous sites of focal endochondral fracture callus. Mechanical failure of the fibrous perichondral ring leads to further collapse and shortening without obvious functional impairment of the fibrous ossification groove. Perinatal lethal OI provides insight into how a molecular disorder predominantly of Type I collagen metabolism results in pathology of numerous tissues, leading to severe skeletal dysplasia without primarily affecting chondrogenesis.

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.

The topographic organization of repetitive DNA in the human nucleolus

The nucleolus is a highly specialized nuclear domain where ribosomal DNA (rDNA) is transcribed and preribosomes are assembled. We investigated the molecular organization of the human lymphocyte nucleolus by fluorescence in situ hybridization and confocal laser scanning microscopy and found that transcribed rDNA and nontranscribed ribosomal intergenic spacer (IGS) sequences colocalized to discrete regions frequently on the nucleolar periphery of phytohemagglutinin-stimulated cells. The 5S rDNA gene cluster located on the long arm of chromosome 1 was not regularly associated with the nucleolus. Short interspersed (SINE) Alu elements detected by BLUR 11 were distributed diffusely throughout the nucleus but were severely underrepresented in the nucleolus, whereas an Alu element subcloned from the IGS detected sequences enriched in the nucleolus but sparsely represented in the remainder of the nucleus. In contrast, long interspersed (LINE) Kpn elements, which were located at the nucleolus, were not found in rDNA but were identified outside the ribosomal gene complex on the short arm of at least one acrocentric chromosome. A human chromosome 21-derived alphoid sequence that hybridized to the centromere was localized outside but near the nucleolus, and nonribosomal DNA consisting of a tandemly repeated simple sequence cluster derived from the short arm of chromosome 15 was organized in a compact fashion in the nucleolus. Our study provides new insight into the content and structure of the human nucleolus and illustrates that the unique organization of repetitive DNA on the acrocentric chromosome short arms is reflected in the topographic organization of the nucleolus.

The articular manifestations of Paget's disease of bone. A case report

Disorders of joints are commonly associated with Paget's disease of bone but are often disregarded or attributed to the underlying Pagetic condition. The authors evaluated a 69-year-old man with extensive Paget's disease of bone, degenerative arthritis, calcific periarthritis, and gout. The degenerative arthritis and calcific periarthritis of the shoulders was originally mistaken for Paget's disease of the proximal humerus. The wrist arthritis was attributed to Paget's disease until evaluation of surgical pathology specimens showed intraarticular gouty granulomas. In evaluating and treating a patient with Paget's disease of bone, the orthopedic surgeon should be aware that the successful treatment of associated articular disorders may require therapeutic measures in addition to those used in treating the Paget's disease.

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.

Osteon morphometry in females with femoral neck fractures

The authors measured osteon dimensions and number in specimens of cortical bone obtained from the medial femoral neck (calcar) from nine female patients treated with hemiarthroplasty for femoral neck fractures, and from 12 (seven women, five men) age-matched cadavers without fractures. Specimens from the same location in 14 (seven women, seven men) younger patients treated with total hip arthroplasty (THA) for osteoarthrosis were also studied. There were fewer osteons per unit area and the osteons and their Haversian canals were bigger in the fracture group than in the nonfracture or osteoarthritic groups. Patients with femoral neck fractures also exhibited a decreased Singh index and an increased intracortical porosity compared with age-matched normal controls. By contrast, the osteoarthritic group showed no difference in osteon or Haversian dimensions, osteon number per unit area, Singh index, or in porosity compared with the nonfracture group. These morphometric differences found in the cortical bone of the medial femoral neck may play a role in the incidence of fractures.

Estrogen receptors in fracture healing

Estrogen has profound effects on the regulation of bone metabolism, but its role in fracture healing is unknown. Several recent reports have documented the presence of estrogen receptors in vitro and in diseased tissue. The authors investigated estrogen receptors in nonneoplastic skeletal tissues by immunohistochemical and radioligand binding techniques. Using a fibular osteotomy model of fracture healing in New Zealand rabbits, radioligand binding detected specific, high affinity, saturable estradiol binding sites at low levels throughout fracture healing, with a trend towards a bimodal distribution. Peaks occurred three and 16 days after osteotomy. No estrogen receptor was found by either method in later fracture callus, growth plate, or periosteum. These findings suggest a possible role for estrogen in the early inductive phase and later phase of endochondral ossification in fracture healing.

A longitudinal study of metacarpal bone morphometry in anorexia nervosa

Osteoporosis is a known complication of anorexia nervosa. Although calorie and mineral malnutrition may contribute to changes in bone mass and morphometry, hypoestrogenism is thought to be the most important etiologic factor. In a seven-year longitudinal study of six women aged 19 to 35 years with adolescent-onset anorexia nervosa, the objective was to correlate menstruation and bone morphometry. At the onset of the study, five women were amenorrheic and had abnormal metacarpal bone morphometry. After seven years, three women remained amenorrheic and below 85% of ideal body weight. Anteroposterior roentgenographs of the nondominant second metacarpal taken at the beginning and end of the study revealed an increase in medullary canal diameter (p less than 0.03) and medullary area (p less than 0.04) and a decrease in combined cortical thickness (p less than 0.04) and percent cortical area (p less than 0.02). These findings suggest progressive endosteal resorption in the absence of compensatory periosteal apposition. Such bone remodeling characteristics are distinctly abnormal in this age group. The three women who regained menses showed up to one third less endosteal resorption and less cortical thinning than did the three women who remained amenorrheic. Resumption of menses may be an important milestone in preventing further cortical bone loss in anorexia nervosa.

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.