Paramyxovirus-like inclusions in two cases of pycnodysostosis

Paget's disease of bone-genetic and environmental factors

Paget's disease of bone is generally diagnosed in individuals aged >50 years, usually manifests in one or several bones and is initiated by osteoclast-induced osteolytic lesions. Subsequently, over a period of many years, osteoblastic activity can result in sclerosis and deformation of bone. The prevalence of Paget's disease is highest in the UK and in countries where a large number of residents have ancestors from the UK. Currently, in many countries, the prevalence of the disorder has decreased. A considerable number of affected patients have a family history of Paget's disease and the disorder has an autosomal dominant pattern of inheritance but with incomplete penetrance. A large number of mutations in SQSTM1 (which encodes sequestosome-1; also known as ubiquitin-binding protein p62) seem to account for the susceptibility to develop Paget's disease in some families; the involvement of other genes is currently under investigation. In addition to a genetic cause, environmental factors have been proposed to have a role in the pathogenesis of Paget's disease. Although most evidence has been presented for measles virus as an aetiologic factor, some studies have not confirmed its involvement. The decreasing incidence of Paget's disease, which could be attributed to measles vaccination along with the measles virus nucleocapsid protein induction of Paget's disease lesions in transgenic mice, supports an aetiologic role of the virus.

Mechanisms of the anabolic effects of teriparatide on bone: insight from the treatment of a patient with pycnodysostosis

Pycnodysostosis is an extremely rare genetic osteosclerosis caused by cathepsin K deficiency. We hypothesized that teriparatide, a potent anabolic agent used in the treatment of osteoporosis, might reduce skeletal fragility by activating bone turnover. We studied a typical case of pycnodysostosis in a 37-yr-old woman who exhibited short stature, skull and thorax deformities, and a history of severe fragility fractures. Cathepsin K gene sequencing was performed. Before and after 6 mo of 20 microg/d teriparatide, biochemical markers of bone turnover were measured, and 3D bone structure and microarchitecture was assessed in vivo by HR-pQCT. Qualitative and quantitative analysis of transiliac bone biopsies were performed, and the degree of mineralization was evaluated by quantitative microradiography. In vitro assessment of bone resorption was performed after separation and differentiation of CD14(+) monocytes from peripheral blood. Bone structure assessed by HR-pQCT on the radius and tibia showed augmentation of cortical and trabecular density. Transiliac bone biopsy showed highly increased bone mass (+63% versus age- and sex-matched controls), a decrease in bone remodeling without evidence of active osteoblasts, and a severe decrease in the dynamic parameters of bone formation (mineralizing surfaces, -90% and bone formation rate, -93% versus age- and sex-matched controls). This depressed bone turnover probably explained the increased degree of mineralization. The presence of a novel missense mutation leading to an A141V amino acid substitution confirmed a genetic defect of cathepsin K as the cause of the disease. The deficiency of active osteoclasts was confirmed by an in vitro study that showed a decreased concentration of CD14(+) monocytes (the precursor of osteoclasts) in blood. These osteoclasts had low resorptive activity when incubated on bone slices. After 6 mo of teriparatide, the structure, microarchitecture, and turnover of bone--assessed by HR-pQCT, histology, and bone turnover markers--remained unchanged. Our data strongly suggest that some features of the osteoclastic phenotype--that are absent in pycnodysostosis--are a prerequisite for the anabolic effect of PTH on osteoblasts.

Paget's disease in an archeological population

The aim of this investigation was to study the prevalence and distribution of Paget's disease in an archeological population. Paget's disease, first described over 100 years ago, is a well-recognized chronic disorder involving abnormal bone turnover with established radiological features. Prevalence within modern populations varies both within individual countries and between them. Paleopathological examples are uncommon and sporadically reported both from Europe and the Americas and from many periods of history. A large skeletal assemblage (2,770 individuals) from Barton on Humber, UK, provided an opportunity to examine the prevalence of Paget's disease in one area of the northern England over the period 900-1,850 AD. All bones were examined visually for evidence of Paget's disease of the bone (PDB) and all abnormal bones were examined further by plain radiography. Fifteen cases of probable Paget's disease were found. The overall prevalence was 2.1% in those aged >40 years. The prevalence before 1500 AD was 1.7% and post-1500 AD was 3.1%. The distribution of disease mirrored modern disease, with the lumbar spine, pelvis, and proximal femur being the commonest sites. The prevalence of Paget's disease in the United Kingdom over the last 1,000 years has been assessed. Although there is a trend of increasing prevalence, this did not reach statistical significance. This is likely caused by the small sample size, but this is by far the greatest number of cases of PDB described in a single skeletal assemblage to date. The distribution of lesions within the skeleton is unchanged.

Osteoclasts formed by measles virus-infected osteoclast precursors from hCD46 transgenic mice express characteristics of pagetic osteoclasts

Pagetic osteoclasts (OCLs) are abnormal in size and contain paramyxoviral-like nuclear inclusions that cross-react with antibodies to measles virus (MV). However, the role that MV infection plays in Paget's disease is unknown, because no animal model of Paget's disease is available. Therefore, we targeted a cellular MV receptor, human CD46 (hCD46), to cells in the OCL lineage in transgenic mice using the mouse tartrate-resistant acid phosphatase (TRAP) gene promoter. In vitro infection of OCL precursors from hCD46 transgenic mice with MV significantly increased OCL formation in bone marrow cultures. The numbers of TRAP-positive mononuclear cells and CFU-GM, the earliest identifiable OCL precursor, were also significantly increased. MV-infected OCLs formed from hCD46 marrow were increased in size, contained markedly increased numbers of nuclei, and had increased bone-resorbing capacity per OCL compared with OCLs formed from marrow of nontransgenic littermates. Furthermore, IL-6 and 24-hydroxylase messenger RNA expression levels were increased in MV-infected hCD46 transgenic mouse bone marrow cultures. Treatment of MV-infected hCD46 marrow cultures with a neutralizing antibody to IL-6 blocked the increased OCL formation seen in these cultures. These data demonstrate that MV infection of OCL precursors results in OCLs that have many features of pagetic OCLs, that the enhanced OCL formation is in part mediated by increased IL-6 expression induced by MV infection, and suggest that the hCD46 transgenic mouse may be a useful model for examining the effects of MV infection on OCL formation in vivo.

Paget's disease of bone: indications for treatment and goals of therapy

Paget's disease of bone is a common disorder of unknown etiology characterized by increased bone remodeling and abnormal bone architecture. The pathologic process is initiated by an increase in osteoclast-mediated bone resorption, accompanied by a compensatory increase in bone formation. The increased bone remodeling results in a disorganized mosaic of woven and lamellar bone. This bone is highly vascular and gradually becomes enlarged and structurally weakened. Paget's disease is generally diagnosed in patients older than 40 years of age, usually as an incidental finding. The disease may be monostotic or polyostotic. The pelvis, femur, spine, tibia, skull, and humerus are most commonly involved. Most patients with Paget's disease are asymptomatic. Pain is the most common presenting symptom. Complications of the disease include bowing deformity of the long bones, fracture, and a variety of nerve compression syndromes. Malignant degeneration of Paget's disease is a rare complication. As safer, more effective therapies have become available, the indications for treatment and goals of therapy have changed. The difficult issue that clinicians are currently facing is whether to treat patients with asymptomatic disease. The progressive nature of the disease, the severity of its complications, its potential negative impact on quality of life, and the availability of therapy capable of controlling its activity have led many experts in the field to recommend treatment of asymptomatic patients who have active disease at sites where complications are likely to develop. There are, however, no data to prove that complications can be prevented by decreasing the rate of bone remodeling in Paget's disease, nor any data to define who is at risk for complications. Until more information is available, the management of patients with Paget's disease will continue to be based on clinical observation and theoretical considerations. This review examines the present understanding of Paget's disease, the rationale for the proposed indications for treatment and the goals of therapy.

Genetic linkage of Paget disease of the bone to chromosome 18q

Paget disease is a common bone disease characterized by abnormal osteoclasts that are large, multinucleated, and overactive and that contain paramyxovirus-like nuclear inclusions. There is evidence for a major genetic component to Paget disease, with up to 40% of patients having affected first-degree relatives; however, the locus (loci) and gene(s) involved are unknown. Another bone disorder, familial expansile osteolysis (FEO), although extremely rare, also is characterized by similar osteoclast abnormalities but has an earlier age at onset and a more aggressive clinical progression. The causative gene for FEO has been localized to a region of human chromosome 18q. On the basis of the presence of similar clinical findings and of viral-like nuclear inclusions in osteoclasts, we hypothesized that FEO and Paget disease are allelic versions of the same locus. Therefore, a large kindred with a high incidence of Paget disease was examined to determine if Paget disease was linked to genetic markers in the same region of chromosome 18 as that for FEO. Our analysis yielded a two-point LOD score of 3.40, with the genetic marker D18S42, a marker tightly linked to the FEO locus. This demonstrates that the gene(s) responsible for FEO and that for Paget disease are either closely linked or the same locus.

Paget's disease of bone possible viral basis

In 1974, the first report of the presence of viral-like inclusions in the osteoclasts of patients with Paget's disease appeared (Rebel et al 1974). This observation, first made in France, was followed by confirmatory reports from North America, Europe, and Asia. Although no more compelling hypothesis than a viral etiology has been proposed subsequently, definitive proof of viral etiology is still lacking. This article summarizes the research of the past 22 years, which has been directed at defining the exact nature of the viral-like inclusions that are invariably found in the osteoclasts of Paget's disease.

Dogs, distemper and Paget's disease

The cause of Paget's disease is still unknown, despite many years of intensive study. During this time, evidence has sporadically emerged to suggest that the disease may result from a slow viral infection by one or more of the Paramyxoviruses. More recently, epidemiologic and molecular studies have suggested that the canine paramyxovirus, canine distemper virus, is the virus responsible for the disease. If true, then along with rabies, this would be a further example of a canine virus causing human disease. Studies in the natural host have now supported these findings. Further investigations have proposed that the bony abnormalities seen in Paget's disease are due to the effects of the virus on osteoclastic interleukin-6 and c-FOS production, possibly via the transcription factor NF-kappa B.

Extracellular protein secretion of cultured normal and Pagetic osteoblasts

Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) has been used to map the extracellular secretory activity of normal osteoblasts. The proteins osteonectin, bone sialoprotein, and both the C-telopeptide of collagen I together with collagen I have now been positionally identified. In addition the secretory differences which exist between normal and Pagetic osteoblasts have been mapped with the Pagetic osteoblasts shown to consistently secrete an altered 30 kDa C-telopeptide of collagen type I. The use of the diphosphonate Pamidronate in the treatment of Paget's disease of bone has beneficial effects with suppression of the bone isoenzyme marker alkaline phosphatase. It has been reported that diphosphonates directly inhibit human osteoblast secretory function as well as osteoclast metabolism. The effects of Pamidronate on the secretory activity of normal and Pagetic osteoblast cultures was also investigated. The extracellular protein secretion of normal and Pagetic osteoblasts was not affected by Pamidronate treatment as assessed by 2-D PAGE. This technique allows a comprehensive multiparameter assessment of extracellular secretory activity in normal and diseased states. The findings show that the Pagetic osteoblasts cultured in vitro are functionally abnormal and they support the hypothesis that the underlying problem in Paget's disease is characterised by disorder of osteoblast and osteoclast interactions.

Paramyxoviruses and Paget's disease

Using the technique of in situ hybridisation, we extended our initial studies of the occurrence of canine distemper and measles virus in Paget's disease. Bone samples from untreated patients and patients treated with 3-amino-hydroxypropylidene 1,1 bisphosphonate pamidronate (APD) were examined for canine distemper nucleocapsid (CDV-N), measles nucleocapsid (MV-N), respiratory syncytial virus fusion (RSV-F), and simian virus 5 haemoglutinin-neuraminidase (SV5-HN) sequences using 35S-labelled sense and antisense riboprobes. Only CDV-N mRNA was detected in osteoclasts, osteoblasts, and mononuclear cells. In untreated Paget's patients, 63.5% were found to have CDV sequences residing in bone cells, and 48.2% of those undergoing APD treatment were still found to have the viral sequences. RSV-F mRNA was only found in one patient. None of the other paramyxoviruses tested were detected. This study shows that CDV can infect a human host and may be an aetiological agent of Paget's disease of bone.

Canine distemper virus transcripts sequenced from pagetic bone

Paget's disease is a chronic disease of the skeleton which is believed to be caused by a persistent virus of the paramyxovirus family. There is still conflict as to the precise identity of the virus(es) involved in causing this disease. Our previous results using in situ hybridisation have implicated distemper as a possible cause of this disease. In order to confirm these results, we have reverse transcribed RNA from pagetic bone and have specifically amplified for distemper and measles sequences using the polymerase chain reaction (PCR) technique. We have found that 8/13 of the patients examined had distemper and 1/10 cases had measles nucleic acids sequestered within their bone cells. One individual was found to have both viruses sequestered in his bone cells. Dideoxy sequencing of the distemper virus PCR products revealed 2% base pair changes in the nucleic acid sequences relative to the Onderstpoort strain of canine distemper. We can conclude that in Paget's disease, canine distemper and possible other paramyxoviruses reside in bone cells and that the persistent nature of the virus may be due to mutations in the viral genome.

Painful diffuse osteosclerosis after intravenous drug abuse

PURPOSE

We identify a new syndrome of acquired painful diffuse osteosclerosis associated with past intravenous drug abuse in two adults.

METHODS

A 28-year-old white woman and a 38-year-old black man with a history of non-A, non-B chronic active hepatitis were referred to us for increasing bone pain that was especially severe in their lower extremities. They were studied at our clinical research center.

RESULTS

Skeletal radiographs documented progressive generalized osteosclerosis. Increased bone mass was confirmed by dual-energy radiography, and bone scintigraphy showed diffusely increased radionuclide accumulation. Serum biochemical studies revealed elevated alkaline phosphatase activity and osteocalcin levels, mild to moderately increased 1,25-dihydroxyvitamin D concentrations, and normal parathyroid hormone levels. In urine, hydroxyproline excretion was elevated, whereas calcium levels were reduced. Iliac crest histomorphometry showed increased rates of bone formation. Hematology, renal function, serum protein electrophoresis, and screening for fluorosis as well as vitamin A and heavy metal poisoning were all normal. Family histories were negative. Both patients were seropositive for antibody against hepatitis C virus as well as against Epstein-Barr virus (antiviral capsid antigen IgG but not IgM). Each subject was seronegative for cytomegalovirus, human immunodeficiency virus (HIV) 1 and 2, and human T-cell lymphotropic virus (HTLV) 1 and 2. Assay for reverse transcriptase in lymphocyte co-culture fluid and polymerase chain reaction studies using HIV-1 primers on peripheral monocyte DNA were negative. Treatment with synthetic salmon calcitonin in both individuals rapidly led to decreased bone pain and to a decline in biochemical parameters of accelerated bone turnover.

CONCLUSION

Painful diffuse osteosclerosis can follow intravenous drug abuse and is possibly caused by parenteral transmission of a virus that in some way stimulates bone formation.

Canine distemper virus localised in bone cells of patients with Paget's disease

The technique of in situ hybridisation was applied using radioactively labelled riboprobes to examine for the presence of canine distemper (CDV) and measles (MV) RNA in Paget's disease of bone. The results indicate that in 41% of Paget's patients, CDV RNA could be detected in osteoclasts, osteoblasts, and osteocytes, but not in controls. In contrast, RNA to the measles virus was not detected. We suggest that CDV may in some cases play a role in the aetiology of Paget's disease.

Retroviral expression in mononuclear blood cells isolated from a patient with osteopetrosis (Albers-Schönberg disease)

We report the presence of reverse transcriptase activity in the supernatant of long-term culture of mononuclear blood cells (monocytes and lymphocytes) isolated from a 27-year-old patient suffering from benign osteopetrosis. The enzyme was purified to homogeneity according to the technique of Chandra and Steel, by chromatography, first on DEAE-cellulose (DE 52) and then on phosphocellulose (P11). After purification, the enzyme was characterized biochemically for its template specificity and ionic requirements. The purified enzyme was able to transcribe poly(rA).(dT)12-18 and poly(rC).(dG)12-18 very efficiently and had a marked preference for Mg2+ ions over Mn2+ ions. The pattern of ionic dependency for this enzyme is similar to that of reverse transcriptases purified from human lymphotropic viruses. The patient was tested and found sero-negative for HIV-1, HIV-2, and HTLV-I and seropositive (immunoglobulin G) for cytomegalovirus. Epstein-Barr virus nuclear antigens (EBNA) were detected in the patient's B lymphocytes. Since reverse transcriptase is the hallmark of retroviruses, we suggest that a retrovirus may be involved in the etiology of osteopetrosis.

Paget's disease of bone

Paget's disease is a common disorder of bone of presumed viral aetiology which, in a minority of patients, may cause severe symptoms. Both calcitonin and the diphosphonates have specific anti-pagetic effects. Newer diphosphonates, unlike etidronate, do not impair mineralization, and when they become available these will be the drugs of choice. Until that time, both calcitonin and etidronate continue to have a useful place in the management of this disorder.

Osteoclasts in human osteopetrosis contain viral-nucleocapsid-like nuclear inclusions

We report the discovery of nuclear inclusions in the osteoclasts of three unrelated patients with benign osteopetrosis that resemble the osteoclast inclusions characteristic of Paget's disease of bone. These inclusions are morphologically and dimensionally identical to the nucleocapsids of a virus of the Paramyxoviridae family. Supporting a possible viral association with benign osteopetrosis in the observation of the presence of antigens of respiratory syncytial virus, measles virus, and/or mumps virus in the cells of all five patients whose paraffin-embedded bone specimens were tested. These included two patients whose osteoclasts contained nuclear inclusions. No patients with the malignant form of the disease have been studied. There is as yet no proof that a virus is causally related to human osteopetrosis even though a virus can produce an avian form of the disease.