Frequency and characteristics of familial aggregation of Paget's disease of bone

Paget's disease of bone is not associated with common polymorphisms in interleukin-6, interleukin-8 and tumor necrosis factor alpha genes

BACKGROUND

Cytokines, specially interleukin (IL)-6, play an important role in the differentiation and activation of osteoclasts and might be involved in osteoblast stimulation in Paget's disease of bone (PDB).

OBJECTIVES

The aim of this study was to investigate the association of polymorphisms in IL-6, IL-8 and tumor necrosis factors-alpha (TNFA) genes among Spanish patients with PDB.

METHODS

We studied four single nucleotide polymorphisms (-174 G>C IL-6, -251 T>A IL-8, -238 G>A TNFA and -308 G>A TNFA) in 172 PDB patients and 150 healthy controls. Distribution of alleles and pro-inflammatory genotypes were studied for association with the presence of the disease and with clinical and laboratory data, as well as the response to bisphosphonate treatment in PDB patients.

RESULTS

We found no statistically significant association between genotype and allele distribution of any of the cytokines polymorphism studied and PDB. No association between the clinical and therapeutic characteristics of PDB and the investigated polymorphism were found.

CONCLUSIONS

This study does not support the hypothesis that the analyzed IL6, IL8 and TNFA polymorphism are associated with PDB.

Genome-wide association study identifies variants at CSF1, OPTN and TNFRSF11A as genetic risk factors for Paget's disease of bone

Paget's disease of bone (PDB) is a common disorder with a strong genetic component characterized by focal increases in bone turnover, which in some cases is caused by mutations in SQSTM1. To identify additional susceptibility genes, we performed a genome-wide association study in 750 individuals with PDB (cases) without SQSTM1 mutations and 1,002 controls and identified three candidate disease loci, which were then replicated in an independent set of 500 cases and 535 controls. The strongest signal was with rs484959 on 1p13 near the CSF1 gene (P = 5.38 x 10(-24)). Significant associations were also observed with rs1561570 on 10p13 within the OPTN gene (P = 6.09 x 10(-13)) and with rs3018362 on 18q21 near the TNFRSF11A gene (P = 5.27 x 10(-13)). These studies provide new insights into the pathogenesis of PDB and identify OPTN, CSF1 and TNFRSF11A as candidate genes for disease susceptibility.

Pathogenesis of Paget's disease of bone

Paget's disease of bone is a common condition characterised by increased and disorganised bone turnover which can affect one or several bones throughout the skeleton. These abnormalities disrupt normal bone architecture and lead to various complications such as bone pain osteoarthritis, pathological fracture, bone deformity, deafness, and nerve compression syndromes. Genetic factors play an important role in PDB and mutations or polymorphisms have been identified in four genes that cause classical Paget's disease and related syndromes. These include TNFRSF11A, which encodes RANK, TNFRSF11B which encodes osteoprotegerin, VCP which encodes p97, and SQSTM1 which encodes p62. All of these genes play a role in the RANK-NFkappaB signalling pathway and it is likely that the mutations predispose to PDB by disrupting normal signalling, leading to osteoclast activation. Although Paget's has traditionally be considered a disease of the osteoclast there is evidence that stromal cell function and osteoblast function are also abnormal, which might account for the fact that the disease is associated with increased bone formation as well as resorption. Environmental factors also contribute to Paget's disease. Most research has focused on paramyxovirus infection as a possible environmental trigger but evidence in favour of the involvement of viruses in the disease remains conflicting. Other factors which have been implicated as possible disease triggers include mechanical loading, dietary calcium and environmental toxins. Further work will be required to identify additional genetic variants that predispose to Paget's disease and to determine how the causal mutations and predisposing polymorphisms interact with environmental factors to influence bone cell function and cause the focal bone lesions that are characteristic of the disease.

A SQSTM1/p62 mutation linked to Paget's disease increases the osteoclastogenic potential of the bone microenvironment

Paget's disease of bone (PDB) is the second most common bone disease and is characterized by focal bone lesions which contain large numbers of abnormal osteoclasts (OCLs) and very active normal osteoblasts in a highly osteoclastogenic marrow microenvironment. The etiology of PDB is not well understood and both environmental and genetic causes have been implicated in its pathogenesis. Mutations in the SQSTM1/p62 gene have been identified in up to 30% of Paget's patients. To determine if p62 mutation is sufficient to induce PDB, we generated mice harboring a mutation causing a P-to-L (proline-to-leucine) substitution at residue 394 (the murine equivalent of human p62(P392L), the most common PDB-associated mutation). Bone marrow cultures from p62(P394L) mice formed increased numbers of OCLs in response to receptor activator of NF-kappaB ligand (RANKL), tumor necrosis factor alpha (TNF-alpha) or 1alpha,25-(OH)(2)D(3), similar to PDB patients. However, purified p62(P394L) OCL precursors depleted of stromal cells were no longer hyper-responsive to 1alpha,25-(OH)(2)D(3), suggesting effects of the p62(P394L) mutation on the marrow microenvironment in addition to direct effects on OCLs. Co-cultures of purified p62(P394L) stromal cells with either wild-type (WT) or p62(P394L) OCL precursors formed more OCLs than co-cultures containing WT stromal cells due to increased RANKL production by the mutant stromal cells. However, despite the enhanced osteoclastogenic potential of both OCL precursors and marrow stromal cells, the p62(P394L) mice had histologically normal bones. These results indicate that this PDB-associated p62 mutation is not sufficient to induce PDB and suggest that additional factors acting together with p62 mutation are necessary for the development of PDB in vivo.

Pathogenesis and management of Paget's disease of bone

Paget's disease of bone is a common disease characterised by focal areas of increased bone turnover, affecting one or several bones throughout the skeleton. Paget's disease is often asymptomatic but can be associated with bone pain and other complications such as osteoarthritis, pathological fracture, bone deformity, deafness, and nerve compression syndromes. Genetic factors have an important role in this disease, and mutations have been identified in four genes that cause Paget's disease and related syndromes. The most important of these is Sequestosome 1 (SQSTM1), which is a scaffold protein in the nuclear factor kappaB (NFkappaB) signalling pathway. Patients with SQSTM1 mutations have severe Paget's disease of bone and a high degree of penetrance with increasing age. Environmental factors also contribute. Most research has focused on paramyxovirus infection as a possible trigger, but evidence for this notion is conflicting. Other potential triggers include deficiency of dietary calcium and repetitive mechanical loading of the skeleton. Medical management of Paget's disease of bone is based on giving inhibitors of osteoclastic bone resorption, and bisphosphonates are the treatment of first choice. Bisphosphonate therapy is primarily indicated for patients who have bone pain arising from increased metabolic activity in affected bones. Bisphosphonate therapy is highly effective at reducing bone turnover, and it has been shown to heal radiological lesions and restore normal histology; however, the long-term effects of bisphosphonates on disease progression have not been adequately studied. No firm evidence as yet exists to show that bisphosphonates can prevent the development of complications of Paget's disease of bone, and further work is needed to address the effects of treatment on long-term clinical outcome.

Founder effect in different European countries for the recurrent P392L SQSTM1 mutation in Paget's Disease of Bone

Paget's Disease of Bone (PDB) is one of the most frequent metabolic bone diseases, affecting 1-5% of Western populations older than 55 years. Mutations in the sequestosome1 (SQSTM1) gene cause PDB in about one-third of familial PDB cases and in 2.4-9.3% of nonfamilial PDB cases, with the 1215C-->T (P392L) mutation being the most frequent one. We investigated whether a founder effect of the P392L SQSTM1 mutation was present in Belgian (n = 233), Dutch (n = 82), and Spanish (n = 64) patients without a PDB family history. First, direct sequencing analysis of exon 8 in these three populations showed that the P392L mutation occurred in 17 Belgian patients (7.3%), three Dutch patients without a family history (3.7%), and two Dutch patients with a family history. In the Spanish population, 15.6% of patients (n = 10) had the P392L mutation, including one homozygous mutant. This is by far the highest mutation frequency of all populations investigated so far. Next, we examined the genetic background of 33 mutated chromosomes by analyzing haplotypes. We genotyped four single-nucleotide polymorphisms (SNPs) in exon 6 and the 3'-untranslated region of SQSTM1 (rs4935C/T, rs4797G/A, rs10277T/C, and rs1065154G/T) and used software programs WHAP and PHASE to reconstruct haplotypes. Finally, allele-specific primers allowed us to assign the mutation to one of the two haplotypes from each individual. Sequencing results revealed that all 33 P392L mutations were on the CGTG (H2) haplotype. The chance to obtain this result due to 33 independent mutation events is 3.97 x 10(-14), providing strong evidence for a founder effect of the P392L SQSTM1 mutation in Belgian, Dutch, and Spanish patients with PDB.

Protocol for stage 2 of the GaP study (genetic testing acceptability for Paget's disease of bone): a questionnaire study to investigate whether relatives of people with Paget's disease would accept genetic testing and preventive treatment if they were available

BACKGROUND

Paget's disease of bone (PDB) disrupts normal bone architecture and causes pain, deformity, deafness, osteoarthritis, and fractures. Genetic factors play a role in PDB and genetic tests are now conducted for research purposes. It is thus timely to investigate the potential for a clinical programme of genetic testing and preventative treatment for people who have a family history of PDB. This study examines the beliefs of relatives of people with PDB. It focuses particularly on illness and treatment representations as predictors of the acceptability and uptake of potential clinical programmes. Illness representations are examined using Leventhal's Common Sense Self-Regulation Model while cognitions about treatment behaviours (acceptance of testing and treatment uptake) are conceptualised within the Theory of Planned Behaviour.

METHODS/DESIGN

A postal questionnaire of non-affected relatives of people with Paget's disease. The sample will include relatives of Paget's patients with a family history of Paget's disease and relatives of Paget's patients without a family history of Paget's disease. The questionnaire will explore whether a range of factors relate to acceptability of a programme of genetic testing and preventive treatment in relatives of Paget's disease sufferers. The questionnaire will include several measures: illness representations (as measured by the Brief Illness Perceptions Questionnaire); treatment representations (as measured by Theory of Planned Behaviour-based question items, informed by a prior interview elicitation study); descriptive and demographic details; and questions exploring family environment and beliefs of other important people. Data will also be collected from family members who have been diagnosed with Paget's disease to describe the disease presentation and its distribution within a family.

DISCUSSION

The answers to these measures will inform the feasibility of a programme of genetic testing and preventive treatment for individuals who are at a high risk of developing Paget's disease because they carry an appropriate genetic mutation. They will also contribute to theoretical and empirical approaches to predicting diagnostic and treatment behaviours from the combined theoretical models.

The osteoclast: friend or foe?

Bone is a dynamic organ constantly remodeled to support calcium homeostasis and structural needs. The osteoclast is the cell responsible for removing both the organic and inorganic components of bone. It is derived from hematopoietic progenitors in the macrophage lineage and differentiates in response to the tumor necrosis factor family cytokine receptor activator of NF kappa B ligand. alpha v beta 3 integrin mediates cell adhesion necessary for polarization and formation of an isolated, acidified resorptive microenvironment. Defects in osteoclast function, whether genetic or iatrogenic, may increase bone mass but lead to poor bone quality and a high fracture risk. Pathological stimulation of osteoclast formation and resorption occurs in postmenopausal osteoporosis, inflammatory arthritis, and metastasis of tumors to bone. In these diseases, osteoclast activity causes bone loss that leads to pain, deformity, and fracture. Thus, osteoclasts are critical for normal bone function, but their activity must be controlled.

Sequestosome 1 (SQSTM1) mutations in Paget's disease of bone from the United States

Paget's disease of bone (PDB) is a localized bone disease characterized by excessive bone resorption due to overactive osteoclasts. Seven genetic loci (PDB1-PDB7) have been reported for late-onset PDB. PDB3 is the only locus where a gene, sequestosome 1 (SQSTM1), has been identified. Mutations in SQSTM1 have been associated with both sporadic and hereditary PDB in different populations. However, the SQSTM1 mutation frequency in PDB patients from a more heterogeneous population has never been reported. To investigate this, we determined the frequency of mutations in patients from the United States. Blood was collected from sporadic and hereditary PDB patients in the United States. DNA was isolated from whole blood or from serum. The SQSTM1 sequence was determined for exons and intron/exon junctions from whole blood and serum. A total of 112 (39 hereditary, 73 sporadic) samples were collected. Eight mutations were found in hereditary PDB patients, for a mutation frequency of 20.5% (95% confidence interval [CI] 10.8-35.5%) and did not differ significantly from mutation rates observed in studies in Canada, Great Britain, and The Netherlands. No mutations were found in sporadic patients, for a frequency of 0% (95% CI 0.0-5.0%), which was statistically significantly lower than the mutation rates previously observed in populations from Australia (P = 0.009), Canada (P = 0.008), Great Britain (P = 0.02), and France (P = 0.04) but not compared to rates from Belgium, The Netherlands, and Italy. Four out of five families with the P392L mutation carried it on the H2 haplotype. Mutations in SQSTM1 seem to contribute to the pathogenesis of PDB in hereditary, but not sporadic, patients in the United States.

Gene expression profiling in Paget's disease of bone: upregulation of interferon signaling pathways in pagetic monocytes and lymphocytes

We examined the gene expression profile of genes involved in bone metabolism in 23 patients with PD compared with 23 healthy controls. We found a significant overexpression of the genes of the IFN pathway along with a downregulation of tnf-alpha. Our result suggest that IFN-mediated signaling may play important roles in aberrant osteoclastogenesis of PD.

INTRODUCTION

Paget's disease of bone (PD) is characterized by focal regions of highly exaggerated bone remodeling and aberrant osteoclastogenesis. Under physiological conditions, circulating monocytes may serve as early progenitors of osteoclasts and along with peripheral blood lymphocytes produce a wide variety of factors important in bone metabolism. Nevertheless, little is known about the roles of circulating monocytes and lymphocytes in relation to the pathological bone turnover in PD.

MATERIALS AND METHODS

In this study, we aimed at investigating the gene expression pattern of PD using quantitative real-time PCR in monocytes and lymphocytes isolated from peripheral blood mononuclear cells (PBMCs). Fifteen genes known to be involved in osteoclastogenesis were studied in cells from 23 patients with PD and in cells from 23 healthy controls. Eight human genes including ifn-alpha (3.48-fold, p < 0.001), ifn-beta (2.68-fold, p < 0.001), ifn-gamma (1.98-fold, p = 0.002), p38 beta2 mapk (2.47-fold, p = 0.002), ifn-gammar1 (2.03-fold, p = 0.01), ifn-gammar2 (1.81-fold, p = 0.02), stat1 (1.57-fold, p = 0.037), and tnf-alpha (-2.34, p < 0.001) were found to be significantly altered in pagetic monocytes compared with monocytes of healthy controls.

RESULTS

In pagetic lymphocytes, significant changes in the expression of ifn-alpha (2.17-fold, p < 0.001), ifn-beta (2.13-fold, p = 0.005), ifn-gamma (1.89-fold, p < 0.001), ifn-gammar1 (1.02-fold, p = 0.04), ifn-gammar2 (1.01-fold, p = 0.031), stat2 (1.79-fold, p < 0.001), and tnf-alpha (-1.49, p < 0.001) were found compared with lymphocytes of healthy controls. Furthermore, IFN-gamma protein was significantly elevated in the sera of PD patients (18.7 +/- 6.69 pg/ml) compared with healthy controls (3.87 +/- 6.48 pg/ml, p = 0.042).

CONCLUSIONS

In conclusion, our data suggest that novel pathways mainly related to the IFN-mediated signaling may play important roles in the aberrant osteoclastogenesis of PD.

Identification of a major locus for Paget's disease on chromosome 10p13 in families of British descent

Mutations of SQSTM1 are an important cause of PDB, but other genes remain to be discovered. A major susceptibility locus for PDB was identified on chromosome 10p13 by a genome-wide linkage scan in families of British descent, which accounted for the vast majority of cases not caused by SQSTM1 mutations.

INTRODUCTION

Paget's disease of bone (PDB) has a strong genetic component, and several susceptibility loci have been identified by genome-wide linkage scans. We previously identified three susceptibility loci for PDB using this approach on chromosomes 5q35, 2q36, and 10p13 in 62 families of mainly British descent, but subsequently, mutations in the SQSTM1 gene were found to be the cause of PDB in 23 families from this cohort. Here we reanalyzed the results of our genome-wide search in families from this cohort who did not have SQSTM1 mutations.

MATERIALS AND METHODS

The study population consisted of 210 individuals from 39 families of predominantly British descent with autosomal dominant inheritance of PDB in whom SQSTM1 mutations had been excluded by mutation screening. The average family size was 5.44 +/- 3.98 (SD) individuals (range, 2-24 individuals). Genotyping was performed using standard techniques with 382 microsatellite markers spaced at an average distance of 9.06 cM throughout the autosomes. Multipoint linkage analysis was performed using the GENEHUNTER program under models of homogeneity and heterogeneity.

RESULTS

Multipoint parametric linkage analysis under a model of homogeneity and nonparametric linkage analysis under a model of heterogeneity both showed strong evidence of linkage to a single locus on chromosome 10p13 (LOD score, +4.08) close to the marker D10S1653 at 41.43cM. No evidence of linkage was detected at the chromosome 2q36 locus previously identified in this population, and linkage to other candidate loci previously implicated in the pathogenesis of PDB was excluded.

CONCLUSIONS

We conclude that there is an important susceptibility gene for PDB on chromosome 10p13 in families of British descent and find no evidence to support the existence of a susceptibility locus on chromosome 2q36 or other previously identified candidate loci for PDB in this population. The gene that lies within the 10p13 locus seems to account for the development of PDB in the vast majority of families of British descent who do not carry SQSTM1 mutations.

Ubiquitin-mediated signalling and Paget's disease of bone

Multiple steps in the RANK-NF-κB signalling pathway are regulated by ubiquitylation. Mutations affecting different components of this pathway, including the ubiquitin binding p62 signalling adapter protein, are found in patients with Paget's disease of bone or related syndromes. Here, we review the molecular defects and potential disease mechanisms in these conditions and conclude that the mutations may confer a common increased sensitivity of osteoclasts to cytokines, resulting in disordered NF-κB-dependent osteoclast function. Modulation of the osteoclast RANK-NF-κB signalling axis may represent a viable therapeutic strategy for Paget's disease and other conditions where excessive bone resorption or remodelling is a feature.

Publication history: Republished from Current BioData's Targeted Proteins database (TPdb; ).

The molecular pathogenesis of Paget disease of bone

Paget disease of bone (PDB) is a condition characterised by increased bone remodelling at discrete lesions throughout the skeleton. The primary cellular abnormality in PDB involves a net increase in the activity of bone-resorbing osteoclasts, with a secondary increase in bone-forming osteoblast activity. Genetic factors are known to play an important role, with mutations affecting different components of the RANK–NF-κB signalling pathway having been identified in patients with PDB and related disorders. Whilst the disease mechanism in these cases is likely to involve aberrant RANK-mediated osteoclast NF-κB signalling, the precise relationship between other potential contributors, such as viruses and environmental factors, and the molecular pathogenesis of PDB is less clear. This review considers the roles of these different factors in PDB, and concludes that a fuller understanding of their contributions to disease aetiology is likely to be central to future advances in the clinical management of this debilitating skeletal disorder.

Identification of sex-specific associations between polymorphisms of the osteoprotegerin gene, TNFRSF11B, and Paget's disease of bone

We studied the role of TNFRSF11B polymorphisms on the risk to develop Paget's disease of bone in a Belgian study population. We observed no association in men, but a highly significant association was found in women, and this was confirmed in a population from the United Kingdom.

INTRODUCTION

Juvenile Paget's disease has been shown to be caused by mutations in TNFRSF11B encoding osteoprotegerin. Although mutations in this gene have never been found in patients with typical Paget's disease of bone (PDB), there are indications that polymorphisms in TNFRSF11B might contribute to the risk of developing PDB.

MATERIALS AND METHODS

We recruited a population of 131 Belgian patients with sporadic PDB and 171 Belgian controls. By means of the HapMap, we selected 17 SNPs that, in combination with four multimarker tests, contain most information on common genetic variation in TNFRSF11B. To replicate the findings observed in the Belgian study population, genotyping data of SNPs generated in a UK population were reanalyzed.

RESULTS

In our Belgian study population, associations were found for two SNPs (rs11573871, rs1485286) and for one multimarker test involving rs1032129. When subsequently analyzing men and women separately, these associations turned out to be driven by women (56 cases, 78 controls). In addition, three other tagSNPs turned out to be associated in women only. These were rs2073617 (C950T), rs6415470, and rs11573869. Reanalysis of genotyping data from a UK study population indicated that the associations found for C950T and C1181G were also exclusively driven by women (146 cases, 216 controls). Meta-analysis provided evidence for risk increasing effects of the T allele of C950T and the G allele of C1181G in the female population (p = 0.002 and 0.003, respectively). The haplotypes formed by the SNPs associated in the Belgian population were also distributed differentially between female cases and controls.

CONCLUSIONS

We showed for the first time that SNPs influencing the risk to develop PDB could be sex-specific. Further research is necessary to identify the causative variants in TNFRSF11B and to elucidate the molecular pathogenic mechanism.

Delayed development of Paget's disease in offspring inheriting SQSTM1 mutations

Familial Paget's disease is associated with mutations in SQSTM1. We compared the age at diagnosis and severity of Paget's disease in parents with SQSTM1 mutations to their offspring who inherited a mutation. At any given age, the offspring were less likely to be diagnosed with Paget's disease and had less severe disease than their parents.

INTRODUCTION

Mutations in sequestosome 1 (SQSTM1) occur in 25-50% of cases of familial Paget's disease and are thought to be disease-causing. We sought to determine whether there are differences in age at diagnosis and severity of disease in parents and their offspring who share the same genetic predisposition to Paget's disease.

MATERIALS AND METHODS

Eighty-four offspring from 10 families (29 index patients with Paget's disease) with mutations in SQSTM1 were approached, and 58 agreed to participate. The ubiquitin-binding domain region of SQSTM1 was sequenced, and the presence or absence of the known mutation was established. The presence of Paget's disease in offspring who had inherited an SQSTM1 mutation was determined by bone scintigraphy and measurement of serum alkaline phosphatase (ALP).

RESULTS

Twenty-three of 58 offspring had inherited a germline mutation in SQSTM1. The mean ALP was 77 U/liter in offspring with mutations and 72 U/liter in those without mutations (p=0.84). Scintiscans from four offspring (mean age, 45 years; mean ALP, 139 U/liter; mean skeletal involvement, 6%) showed evidence of Paget's disease but were normal in the other 19 (mean age, 44 years; mean ALP, 64 U/liter). In comparison, in the 15 parents of the 23 offspring, the mean age of diagnosis was 48 years, the mean ALP was 850 U/liter, and the mean skeletal involvement was 30%. There was a 63% reduction in the risk of being diagnosed with Paget's disease at a comparable age in the offspring compared with the parents (p=0.028).

CONCLUSIONS

Only 17% of offspring inheriting an SQSTM1 mutation had evidence of Paget's disease on scintigraphy, and this was diagnosed at a later age and was less extensive than in their affected parents. SQSTM1 thus shows incomplete penetrance. The data are consistent with the hypothesis that an environmental factor is important in the pathogenesis and clinical phenotype of familial Paget's disease and that exposure to this factor may be falling.

[Therapy of Paget's disease]

Paget's disease of bone, an often undiagnosed metabolic bone disease, can lead to dramatic skeletal changes with enlargement and bowing of the affected bones. The etiology of this localized bone disease has not yet been determined. Genetic factors and viral infections may be involved. Recently, the treatment options for Paget's disease have been greatly improved due to the development of potent bisphosphonates. These agents inhibit osteoclastic bone resorption and allow the suppression of the excessive bone turnover in Paget's disease. This leads to a stabilization of affected bones and to symptomatic improvements. Treatment should be initiated early after diagnosis to limit the extent of damage. The article gives an overview of recent perspectives on epidemiology, diagnosis, and treatment of the disease according to the new German guidelines for the diagnosis and therapy of Paget's disease.

Contribution of genetic factors to the pathogenesis of Paget's disease of bone and related disorders

Paget's disease of bone (PDB) is a common condition with a strong genetic component that is characterized by focal increases in bone turnover, leading to bone deformity, pathological fractures, and various other complications. Several rare disorders have also been described that show phenotypic overlap with PDB. Genome-wide searches have identified several susceptibility loci for PDB and PDB-like disorders, and mutations that cause these disorders have now been identified in four genes, all of which are involved in the RANK-NF-kappaB signaling pathway. Mutations in SQSTM1, which encodes an important scaffold protein in this pathway, have been found to be a common cause of classical PDB. Thus far, all disease-causing mutations in SQSTM1 affect the ubiquitin-associated (UBA) domain of the gene product and cause loss of ubiquitin binding. The rare PDB-like disorders of familial expansile osteolysis, early-onset familial PDB, and expansile skeletal hyperphosphatasia are caused by duplication mutations in exon 1 of the TNFRSF11A gene, which encodes the RANK receptor. This gene does not seem to be involved in the pathogenesis of classical PDB. Inactivating mutations in the TNFRSF11B gene, which encodes osteoprotegerin, cause juvenile PDB, and TNFRSF11B polymorphisms seem to increase the risk of classical PDB. The rare syndrome of hereditary inclusion body myopathy, PDB, and frontotemporal dementia (IBMPFD) is caused by mutations in the VCP gene, which is involved in regulating I-kappaB degradation by the proteasome. The disease-causing mutations in VCP cluster in and around a domain involved in ubiquitin binding. Whereas SQSTM1 has emerged as an important gene for classical PDB, most kindreds with familial PDB do not carry SQSTM1 mutations, indicating that additional genes for PDB remain to be discovered. In light of the molecular defects that have been identified thus far, it seems likely that these genes will also be involved in the RANK-NF-kappaB signaling pathway or its interactions with the ubiquitin-proteasome system.

Paget's disease of bone in Italy

Epidemiological studies of Paget's disease of bone (PDB) suggest a pronounced geographical variation in the prevalence of the disease and a decrease in prevalence and clinical severity over time. To analyze epidemiological and clinical features of PDB in Italy, we recently established a registry of Italian PDB cases and performed radiological, biochemical, and bone scan surveys in the towns of Siena and Turin. The overall prevalence of PDB in Italy varied between 0.7% and 2.4%. Prevalence rates increased with age and were higher in men than in women. We observed clinically confirmed familial aggregation in 15-26% of cases. Pedigree analysis indicated an autosomal dominant pattern of inheritance with variable penetrance. SQSTM1 gene analysis in two Italian studies revealed the presence of at least three different mutations accounting for both familial and sporadic cases. Interestingly, no decrease in the prevalence of PDB over time was observed, the opposite of what is described in populations of British descent. However, clinical severity of PDB cases included in the Registry in 2002-2004 seemed reduced with respect to that of PDB patients from the previous epidemiological studies, including a 1950-1956 Italian study. Of interest, a consistent association between PDB and animal-related factors and a significantly higher prevalence of the disease in rural than in urban districts were observed. These findings are in keeping with an important role of the environment in the pathogenesis of PDB, perhaps facilitating the expression of the disease in genetically susceptible subjects. Finally, there was also preliminary evidence indicating regional clustering of PDB in Italy, with a concentration of cases in rural districts of Campania and Tuscany. These districts may represent high prevalence areas of PDB in Italy, similar to what has been observed in other countries. Extrapolation estimates suggest that approximately 150,000-300,000 subjects may be affected with PDB in our country. These results confirm PDB to be the most common bone remodeling disorder in elderly people in Italy, excluding osteoporosis.

Sequestosome 1: mutation frequencies, haplotypes, and phenotypes in familial Paget's disease of bone

Mutations of the SQSTM1/p62 gene are commonly observed in PDB. Screening an updated sample from Quebec and using previously published data from other populations, we compared frequency estimates for SQSTM1/p62 mutations and haplotype distribution. The P392L mutation was the most prevalent, embedded in two different haplotypes, possibly shared by other populations. We also examined the phenotype and penetrance of P392L.

INTRODUCTION

There is accumulating evidence that supports a contribution of genetic factors in the etiology of Paget's disease of bone (PDB), and several genetic loci have been suggested for the disorder. The sequestosome1/p62 (SQSTM1/p62) gene was the first gene identified to have a role in PDB, with 14 mutations reported to date.

MATERIAL AND METHODS

To evaluate the importance of the SQSTM1/p62 mutations in PDB, we recruited, sequenced, and genotyped a total of 123 carriers from 20 families in addition to 214 unrelated PDB patients. We compared the frequency of SQSTM1/p62 mutations in familial and unrelated cases among different populations. Finally, we examined the phenotypic expression and penetrance of the P392L mutation in the Quebecois families.

RESULTS AND CONCLUSIONS

The 14 mutations reported in SQSTM1/p62 all affect the ubiquitin-associated domain of the protein. The P392L mutation is the most commonly observed mutation in PDB patients and was consistently found in unrelated and familial PDB cases in the populations tested. Analysis of adjacent polymorphisms suggests that P392L is associated with two different haplotypes in the Quebecois patients, similar to what has been observed in European populations. In Quebec, both haplotypes had similar frequencies in unrelated P392L carriers, whereas one haplotype was predominant in the other populations studied. These data suggest that these two haplotypes, possibly introduced by European founders in the Quebecois population, were equally distributed in the succeeding generations. Finally, the P392L mutation is transmitted as an autosomal dominant trait in the Quebecois families, with a high but incomplete penetrance peaking after age 60. The large phenotypic variability and similarity between unrelated and familial cases, respectively, remain unexplained and require further research.

Evidence for increased clinical severity of familial and sporadic Paget's disease of bone in Campania, southern Italy

The analysis of 236 Italian patients with Paget's bone disease showed higher clinical severity and greater frequency of neoplastic degeneration among patients who live or descend from individuals living in the Campania region (southern Italy). A prevalent involvement of the spine and the skull, the sites preferentially involved in giant cell tumors complicating Paget's disease, was also shown in familial cases from this geographical region.

INTRODUCTION

The Campania region in southern Italy has been recently indicated as a high prevalence area for Paget's disease of bone (PDB), and most pagetic families with multiple occurrence of neoplasms in affected members were from this geographical region.

MATERIALS AND METHODS

We evaluated the PDB epidemiological characteristics in 125 patients from Campania in comparison with 111 patients from other Italian regions. Twenty-three patients from Campania and 26 patients from other Italian areas had at least one first-degree relative affected by PDB (familial cases). The remaining patients made up the sporadic cases.

RESULTS

Among subjects from Campania, the patients in the familial group tended to come from larger families and showed at diagnosis higher serum total alkaline phosphatase, larger extension of disease, and earlier mean age with respect to patients with PDB of the sporadic group. The skull, spine, and humerus were the sites preferentially involved in the familial cases. In contrast, no such differences were observed between familial and sporadic PDB cases among patients from the other geographical areas, except for a lower age at diagnosis. An increased PDB clinical severity was finally observed in the PDB cohort from Campania in comparison with patients from other Italian regions. Neoplastic degeneration of pagetic bones (osteosarcoma and giant cell tumor) was exclusively observed in patients with polyostotic PDB from Campania.

CONCLUSIONS

We showed a higher clinical severity of PDB with occurrence of neoplastic degeneration in the high prevalence area of Campania, with its maximum expression in cases with familial disease. This peculiar pattern might be traced to genetic predisposition and/or to the abnormal impact of a still undefined environmental trigger.

Identification and molecular characterization of a novel splice-site mutation (G1205C) in the SQSTM1 gene causing Paget's disease of bone in an extended American family

Paget's disease of bone (PDB) is a common late-onset bone disorder characterized by focal areas of abnormal bone remodeling. Positional cloning efforts resulted in the identification of seven genetic loci (PDB1-7) with putative involvement in the pathogenesis of PDB. Meanwhile, the PDB-causing gene from the PDB3 region on chromosome 5q35 has been identified as the SQSTM1 gene. All mutations identified in this gene so far are located in or close to the ubiquitin-associated (UBA) domain of the protein. In 2001, we reported genotyping results of genetic markers located in the PDB3 region in an extended American family, indicating the involvement of the PDB3 locus. Here, we report the identification of a novel mutation (G1205C) in the SQSTM1 gene in this family. The G1205C mutation is located in the splice donor site of intron 7 and reverse-transcription polymerase chain reaction experiments showed that the presence of the C allele results in the production of two abnormal mRNA transcripts. Translation of the first transcript would result in a protein that lacks amino acids 351-388, including 26 amino acids of the second PEST domain in addition to two amino acids of the UBA domain. The second mutant mRNA transcript could result in a truncated protein (390X) that lacks almost the complete UBA domain. PDB mutations that disrupt the function of the PEST domain of SQSTM1 have not been reported before, so probably the pathogenic effect of both transcripts resides in the disruption of the ubiquitin-binding properties of the protein.

p62 ubiquitin binding-associated domain mediated the receptor activator of nuclear factor-kappaB ligand-induced osteoclast formation: a new insight into the pathogenesis of Paget's disease of bone

Paget's disease of bone (PDB) is a debilitating bone disorder characterized by giant osteoclasts, enhanced bone destruction, and irregular bone formation. Recently, mutations in SQSTM1 (also known as p62) have been detected in PDB sufferers, with all mutations resulting in either loss of function or truncation/deletion of the ubiquitin binding-associated (UBA) domain. We hypothesized that mutation in the p62 gene resulting in either deletion or premature termination of the UBA domain accounts for the elevated osteoclastic formation and bone resorption associated with PDB. Remarkably, overexpression of the p62 UBA domain deletion mutant (p62DeltaUBA) significantly enhanced osteoclastogenesis in vitro compared to cells expressing either wild-type p62 (p62WT) or a control vector in a RAW264.7 osteoclastogenic system. Overexpression of p62DeltaUBA potentiated the formation of abnormally large multinucleated osteoclasts and resorption of bone, reminiscent of PDB. Consistent with the enhancement of osteoclastogenesis, overexpression of p62DeltaUBA potentiated receptor activator of nuclear factor-kappaB ligand-induced activation of nuclear factor-kappaB, NFAT, and ERK phosphorylation. Furthermore, as determined by confocal microscopy, deletion of the p62 UBA domain impaired the association of p62 with TRAF6 in the proteasomal compartment. These results suggest that the UBA domain encodes essential regulatory elements required for receptor activator of nuclear factor-kappaB ligand-induced osteoclast formation and bone resorption that may be directly associated with the progression of PDB.

Protocol for stage 1 of the GaP study (Genetic testing acceptability for Paget's disease of bone): an interview study about genetic testing and preventive treatment: would relatives of people with Paget's disease want testing and treatment if they were available?

BACKGROUND

Paget's disease of bone (PDB) is characterised by focal increases in bone turnover, affecting one or more bones throughout the skeleton. This disrupts normal bone architecture and causes pain, deformity, deafness, osteoarthritis, and fractures. Genetic factors are recognised to play a role in PDB and it is now possible to carry out genetic tests for research. In view of this, it is timely to investigate the clinical potential for a programme of genetic testing and preventative treatment for people who have a family history of PDB, to prevent or delay the development of PDB. Evidence from non-genetic conditions, that have effective treatments, demonstrates that patients' beliefs may affect the acceptability and uptake of treatment. Two groups of beliefs (illness and treatment representations) are likely to be influential. Illness representations describe how people see their illness, as outlined in Leventhal's Self-Regulation Model. Treatment representations describe how people perceive potential treatment for their disease. People offered a programme of genetic testing and treatment will develop their own treatment representations based on what is offered, but the beliefs rather than the objective programme of treatment are likely to determine their willingness to participate. The Theory of Planned Behaviour is a theoretical model that predicts behaviours from people's beliefs about the consequences, social pressures and perceived control over the behaviour, including uptake of treatment.

METHODS/DESIGN

This study aims to examine the acceptability of genetic testing, followed by preventative treatment, to relatives of people with PDB. We aim to interview people with Paget's disease, and their families, from the UK. Our research questions are:1. What do individuals with Paget's disease think would influence the involvement of their relatives in a programme of genetic testing and preventative treatment? What do relatives of Paget's disease sufferers think would influence them in accepting an offer of a programme of genetic testing and preventative treatment?

DISCUSSION

Our research will be informed by relevant psychological theory: primarily the Self-Regulation Model and the Theory of Planned Behaviour. The results of these interviews will inform the development of a separate questionnaire-based study to explore these research questions in greater detail.

Mechanisms of Disease: genetics of Paget's disease of bone and related disorders

Paget's disease of bone (PDB) is a common disorder in which focal abnormalities of increased bone turnover lead to complications such as bone pain, deformity, pathological fractures, and deafness. PDB has a strong genetic component and several susceptibility loci for the disease have been identified by genome-wide scans. Mutations that predispose individuals to PDB and related disorders have been identified in four genes. The rare PDB-like syndromes of familial expansile osteolysis, early-onset familial PDB, and expansile skeletal hyperphosphatasia are caused by insertion mutations in TNFRSF11A, which encodes receptor activator of nuclear factor (NF)kappaB (RANK)-a critical regulator of osteoclast function. Inactivating mutations in TNFRSF11B, which encodes osteoprotegerin (a decoy receptor for RANK ligand) cause idiopathic hyperphosphatasia, and polymorphisms in this gene seem to increase the risk for classical PDB. Mutations of the sequestosome 1 gene (SQSTM1), which encodes an important scaffold protein in the NFkappaB pathway, are a common cause of classical PDB. The rare syndrome of hereditary inclusion body myopathy, PDB, and fronto-temporal dementia is caused by mutations in the valosin-containing protein (VCP) gene. This gene encodes VCP, which has a role in targeting the inhibitor of NFkappaB for degradation by the proteasome. Several additional genes for PDB remain to be discovered, and it seems likely that they will also involve the RANK-NFkappaB signaling pathway or components of the proteasomal processing of this pathway, underscoring the critical importance of this signaling pathway in bone metabolism and bone disease.

Paget's Disease of Bone and Genetic Disorders of RANKL/OPG/RANK/NF- B Signaling

Identification of the RANKL/OPG/RANK/NF-kB (receptor activator of nuclear factor kappa-B ligand / osteoprotegerin) signaling pathway as the major regulatory system for osteoclastogenesis began with discovery of these ligands and receptors in the tumor necrosis factor (TNF) superfamily. Subsequently, genetically altered mice revealed physiologic roles for these proteins in bone biology. However, full appreciation of their significance for the human skeleton came from clinical characterization of several extremely rare, heritable disorders followed by discovery of their genetic bases. Familial expansile osteolysis (FEO) is an autosomal dominant disorder featuring constitutive activation of RANK due to an 18-bp tandem duplication in its gene (TNFRSF11A). A similar, 27-bp duplication causes what has been called a familial form of early-onset Paget's disease of bone (PDB2). Expansile skeletal hyperphosphatasia (ESH) is allelic to FEO and PDB2 and involves a 15-bp tandem duplication in TNFRSF11A. Autosomal recessive inheritance of deactivating mutations of the gene encoding OPG (TNFRSF11B) causes most cases of juvenile Paget disease. These disorders feature high bone turnover, deafness during early childhood, "idiopathic external lysis" of adult teeth, and sometimes focal lesions in appendicular bones that mimic active PDB. Biochemical markers indicate rapid skeletal remodeling. In FEO, osteolysis progresses to fat-filled bone rather than to osteosclerosis. Antiresorptive therapy with bisphosphonates can be effective for each disorder.

Manifestations in a family with autosomal dominant bone fragility and limb-girdle myopathy

We report on an unusual family with an autosomal dominant limb-girdle type of myopathy and bone fragility. This family was previously reported by Henry et al. [1958] as autosomal dominant progressive limb girdle "muscular dystrophy" with propensity to fractures and defective healing of long bones. Clinical, biochemical, and radiological aspects were evaluated in eight living relatives in this family (three males and five females) and in eight deceased individuals. The average age-of-onset of the limb-girdle myopathy was 31 years occurring in 87% of affected individuals. The average age of onset of fractures was 24 years occurring in 88% of affected individuals. Biochemical analysis showed a mean alkaline phosphatase (ALP) of 64 U/L (normal 30-120) and borderline high creatine kinase (CK) of 213 U/L (normal 4-220). Radiographs revealed coarse trabeculation, patchy sclerosis, cortical thickening, and narrowing of the medullary cavity with an appearance not considered typical of Paget disease of bone (PDB) or of fibrous dysplasia. Results of nerve conduction studies were normal, and electromyograms and muscle biopsies documented non-specific myopathic changes. There is premature graying with thin hair, thin skin, hernias and the affected individuals appear older than their chronological age, and three members had a clotting disorder. Linkage analysis for markers for the chromosome 9p22.3-q12 locus indicated that the disorder in this family does not segregate with markers in the critical region of limb-girdle/inclusion body myopathy, PDB, and frontotemporal dementia (FTD) [IBMPFD, OMIM #605382]. Sequencing of Valosin-containing protein (VCP), the gene associated with IBMPFD, did not identify mutations. We have excluded linkage to the known loci for limb-girdle type of myopathy and bone disease and excluded several candidate genes. Elucidation of the novel molecular basis of this disorder may provide valuable links between bone, collagen and muscle, and targeted therapeutic options.

Evaluation of the role of Valosin-containing protein in the pathogenesis of familial and sporadic Paget's disease of bone

Paget's disease of bone (PDB) is a common metabolic bone disease of late onset with a strong genetic component. Rarely, PDB can occur as part of a syndrome in which the disease is accompanied by inclusion body myopathy and frontotemporal dementia (inclusion body myopathy, Paget's disease and frontotemporal dementia, IBMPFD). Recently, IBMPFD has been shown to be caused by mutations in Valosin-containing Protein (VCP), which is required for the proteasomal degradation of phosphorylated IkappaB-alpha, a necessary step in the activation of the transcription factor NF-kappaB. Here, we evaluated the role of VCP in the pathogenesis of typical PDB. We conducted mutation screening of VCP in 44 kindreds with familial Paget's disease recruited mainly through clinic referrals in the UK, Australia and New Zealand. We also performed an association study of VCP haplotypes in patients with PDB who did not have a family history of the disease (sporadic PDB). No mutations were found in VCP in three PDB families where there was evidence of allele sharing between affected subjects in the VCP critical region on chromosome 9p13. We failed to detect disease-associated mutations in any of the three exons previously reported to contain IBMPFD mutations in a further 41 PDB families. We found no evidence of allelic association between common VCP haplotypes in a case-control study of 179 sporadic PDB patients and 172 age- and sex-matched controls. Genetic variation in VCP does not appear to be a common cause of familial or sporadic PDB in the absence of myopathy and dementia.

Genetics of Paget's disease of bone

Paget's disease of bone is a chronic bone disease that affects up to 3% of Caucasians older than 55 years. The cause of Paget's disease is unknown but involves genetic factors. Familial cases display an autosomal dominant pattern of inheritance with incomplete penetrance. Genetic heterogeneity has been demonstrated and eight potential susceptibility loci identified. There is sound evidence incriminating Sequestosome 1 (SQSTM1) on the long arm of chromosome 5 (5q35-qter), of which nine mutations have been described in Paget's disease of bone. These mutations are located in exons 7 and 8, which encode a highly conserved ubiquitin-binding domain. The prevalence of SQSTM1 mutations is about 10% in France. Tests for SQSTM1 mutations should be done in patients with Paget's disease of bone, even where the family history is negative. Detection of a mutation allows evaluation of family members to ensure early diagnosis of the disease before complications develop.

The role of immune cells and inflammatory cytokines in Paget's disease and multiple myeloma

The osteoclast (OCL) is the primary cell involved in the pathogenesis of Paget's disease (PD) and the destructive bone process in multiple myeloma (MM). Both of these diseases are characterized by increased numbers of OCLs actively resorbing bone, but they differ in that bone formation is greatly increased in PD and is suppressed in MM. The marrow microenvironment plays a critical role in both disease processes, through the increased expression of inflammatory cytokines that enhance osteoclastogenesis and, in the case of MM, also suppress osteoblast (OBL) activity. In addition, the OCLs in PD are intrinsically abnormal, are markedly increased in number and size, and are hyper-responsive to inflammatory cytokines and 1,25-(OH)2D3. This article discusses the role of immune cells and inflammatory cytokines and chemokines in the increased OCL activity in PD and MM bone disease, as well as the potential role of interleukin-3 in the suppression of OBL activity in MM.

Guidelines for diagnosis and management of Paget's disease of bone in Japan

We here propose guidelines for the diagnosis and management of Paget's disease of bone (PDB) in Japan. These guidelines provide basic information on the epidemiology, pathophysiology, clinical signs and symptoms, diagnosis, indications for treatment, and available therapy, including orthopedic surgery. PDB is a chronic disorder characterized by focal abnormalities of bone turnover. The characteristic feature of PDB is excessive osteoclastic bone resorption coupled to increased and disorganized bone formation. The most common symptom of PDB is pain in involved bones. The most serious complication of PDB is malignant bone or soft-tissue tumor. PDB is uncommon in Japan; our survey in 2003 found 169 patients with PDB. The prevalence of PDB in Japan is 0.15/100 000; in patients aged 55 years or more, the proportion reaches 0.41/100 000. A careful medical history and physical examination are essential for the diagnosis. The diagnosis of PDB is based on finding the typical features on radiographs. Bone scintigraphy and measurement of serum alkaline phosphatase are sensitive means of screening for PDB. Since PDB is a rare disease in Japan, bone biopsy is quite often used to exclude bone metastases. The only evidence-based indication for treatment of PDB is pain in involved bones. In Japan, etidronate and calcitonin are approved by the Ministry of Health, Labour and Welfare for treating PDB, but currently risedronate is also under development for treating PDB in Japan. Indications for surgical intervention in PDB include unstable fractures, osteoarthritis, malignant soft-tissue tumor, osteosarcoma, and bone deformity.

Prevalence and clinical features of Paget's disease of bone in Japan

The present study aimed to evaluate the prevalence and clinical presentation of Paget's disease of bone (PDB) in Japan. As PDB is a very rare disease in Japan, a nationwide mail survey was conducted targeting doctors in the specialty most frequently diagnosing and treating PDB patients in Japan. First, the literature for all case reports in Japan published between January 1990 and December 2002 was reviewed to determine who was diagnosing and treating PDB in Japan. This literature review for all case reports in Japan revealed that 72.1% of cases in Japan were reported from departments of orthopedic surgery. A nationwide two-phase mail survey was conducted for the departments of orthopedic surgery of 2,320 general hospitals accredited by the Japanese Orthopaedic Association. Phase 1 involved determining how many patients with PDB were followed at each hospital. If the answer was one or more, phase 2 of the survey gathered information on the clinical presentation of current patients. The mail survey yielded a final response rate of 75.4% for phase 1 and 87.6% for phase 2. Phase 1 indicated that the prevalence of PDB in Japan is about 2.8 cases per million capita. Phase 2 revealed a slight female predominance, lower frequency of familial clustering, higher frequency of femoral fracture in the affected femur, and a higher ratio of symptomatic PDB in Japan compared with findings in countries displaying a higher prevalence of PDB. The present epidemiological study revealed that the disorder is extremely rare in Japanese individuals, and that some differences exist with regard to the clinical features of PDB between Japanese patients and patients from high-prevalence countries.

Genetics of Paget's disease of bone

PDB (Paget's disease of bone) is a common condition characterized by focal increases in bone turnover affecting one or more sites throughout the skeleton. Genetic factors are important in the pathogenesis of PDB and many families have been described where PDB is inherited in an autosomal-dominant fashion. Several candidate loci for susceptibility to PDB and related syndromes have been identified by genome-wide scans and recent evidence suggests that mutations in genes that encode components of the RANK [receptor activator of NF-κB (nuclear factor-κB)]/NF-κB signalling pathway play an important role in the pathogenesis of this group of diseases. Insertion mutations in the TNFRSF11A gene encoding RANK have been identified as the cause of familial expansile osteolysis, some cases of early onset PDB and expansile skeletal hyperphosphatasia. Inactivating mutations in the TNFRSF11B gene that encodes OPG (osteoprotegerin) have been found to cause the syndrome of juvenile PDB. Polymorphisms in OPG also appear to increase the risk of developing PDB. The most important causal gene for classical PDB is Sequestosome 1 (SQSTM1), which is a scaffold protein in the NF-κB signalling pathway, and mutations affecting the UBA (ubiquitin-associated) domain of this protein occur in between 20–50% of familial and 10–20% of sporadic PDB cases. The rare syndrome of IBMPFD (inclusion body myopathy, PDB and fronto-temporal dementia) is due to mutations in the VCP gene and these also cluster in the domain of VCP that interacts with ubiquitin, suggesting a common disease mechanism with SQSTM1-mediated PDB.

Characteristics and familial aggregation of Paget's disease of bone in Italy

This study examined the characteristics of 147 PDB cases from Italy. Our data showed a reduced clinical severity of PDB with respect to other populations and provided further support of the importance of environmental factors (rural area of residence and animal contact) in the pathogenesis of PDB. Familial aggregation was observed in 15% of cases.

INTRODUCTION

The etiology of Paget's disease of bone (PDB) remains unknown. Current evidence suggests that interactions among genetic or exogenous factors seem to be necessary for disease expression. Major epidemiological studies were performed in the United Kingdom and in other populations of British descent. To date, there are no reliable data on PDB characteristics among the Italian population, and its frequency in different areas of the country remains unknown.

MATERIALS AND METHODS

In an attempt to evaluate clinical characteristics, the proportion of familial cases and the influence of environmental features on the occurrence of the disease, we studied 147 consecutive PDB patients. For all subjects, a detailed medical history was obtained, and constitutional features were recorded. Characteristics of PDB patients were compared with those obtained from 323 consecutive non-Pagetic outpatient control subjects.

RESULTS AND CONCLUSIONS

Of the 147 PDB patients, 22 (15%) had at least one other family member affected, 19 (13%) reported one family member with suspected features of PDB, and 106 (72%) were classified as sporadic PDB. Even though we observed a reduced clinical severity of PDB with respect to other populations (mean number of affected sites, 2.2 +/- 1.6), we did not find any evidence of a decreased severity of the disease over time. We also found an association of PDB with animal contact (odds ratio [OR], 2.22; p < 0.0005) and a significant prevalence of PDB in rural versus urban districts (OR, 2.42; p < 0.0005). Osteoarthritis (45%), fractures (14%), hearing loss (14%), and valvular calcifications (15%) were the most observed complications. Interestingly, the geographical distribution of PDB showed a concentration of cases in rural areas of Campania and Tuscany. These areas may indicate local clustering of PDB cases in Italy, similar to that observed in other countries.

Paget disease of bone

Paget disease of bone (PD) is characterized by excessive bone resorption in focal areas followed by abundant new bone formation, with eventual replacement of the normal bone marrow by vascular and fibrous tissue. The etiology of PD is not well understood, but one PD-linked gene and several other susceptibility loci have been identified, and paramyxoviral gene products have been detected in pagetic osteoclasts. In this review, the pathophysiology of PD and evidence for both a genetic and a viral etiology for PD will be discussed.

Ubiquitin-associated domain mutations of SQSTM1 in Paget's disease of bone: evidence for a founder effect in patients of British descent

Mutations in the UBA domain of SQSTM1 are a common cause of Paget's disease of bone. Here we show that the most common disease-causing mutation (P392L) is carried on a shared haplotype, consistent with a founder effect and a common ancestral origin.

INTRODUCTION

Paget's disease of bone (PDB) is a common condition with a strong genetic component. Mutations affecting the ubiquitin-associated (UBA) domain of sequestosome 1 (SQSTM1) have recently been shown to be an important cause of PDB. The most common mutation results in a proline to leucine amino acid change at codon 392 (P392L), and evidence has been presented to suggest that there may be a recurrent mutation rather than a founder mutation on an ancestral chromosome. Because marked geographical differences exist in the prevalence of PDB, we have investigated the frequency of SQSTM1 mutations in different populations and looked for a founder effect on chromosomes bearing SQSTM1 UBA domain mutations.

MATERIALS AND METHODS

We conducted mutation screening of SQSTM1 and performed haplotype analysis using the PHASE software program in 83 kindreds with familial PDB, recruited mainly through clinic referrals in the United Kingdom, Australia, and New Zealand. Similar studies were conducted in 311 individuals with PDB who did not have a family history and 375 age- and sex-matched controls from the United Kingdom.

RESULTS

The proportion of patients with familial PDB who had SQSTM1 UBA domain mutations varied somewhat between referral centers from 7.1% (Sydney, Australia) to 50% (Perth, Australia), but the difference between centers was not statistically significant. Haplotype analysis in 311 British patients with PDB who did not have a family history and 375 age- and sex-matched British controls showed that two common haplotypes accounted for about 90% of alleles at the SQSTM1 locus, as defined by common single nucleotide polymorphisms (SNPs) in exon 6 (C916T, G976A) and the 3'UTR (C2503T, T2687G). These were H1 (916T-976A-2503C-2687T) and H2 (916C-976G-2503T-2687G). There was no significant difference in haplotype distribution in PDB cases and controls, but the P392L mutation was found on the H2 haplotype in 25/27 cases (93%), which is significantly more often than expected given the allele frequencies in the normal population (odds ratio, 13.2; 95% CI, 3.1-56.4; p < 0.0001). Similar findings were observed in familial PDB, where 12/13 (92%) of P392L mutations were carried on H2 (odds ratio 17.2; 95% CI, 2.2-138; p = 0.001).

CONCLUSIONS

These results provide strong evidence for a founder effect of the SQSTM1 P392L mutation in PDB patients of British descent, irrespective of family history. Our results imply that these individuals share a common ancestor and that the true rate of de novo mutations may be lower than previously suspected.

SQSTM1 and Paget's disease of bone

Mutations in the Sequestosome 1 gene ( SQSTM1; also known as p62) have recently been identified as the cause of 5q35-linked Paget's disease of bone (PDB). All of the mutations identified to date affect the ubiquitin-associated (UBA) domain of SQSTM1, a region of the protein that binds noncovalently to ubiquitin. In this review we consider the possible functional significance of the SQSTM1-ubiquitin interaction, and consequences of the SQSTM1 UBA domain mutations. Clarification of the in vivo roles of SQSTM1 in bone-cell function will be central to improving our understanding of the molecular pathogenesis of PDB and related conditions.

Susceptibility to Paget's disease of bone is influenced by a common polymorphic variant of osteoprotegerin

To clarify the role of the TNFRSF11B gene encoding osteoprotegerin (OPG), in Paget's disease of bone (PDB) we studied TNFRSF11B polymorphisms in an association study of 690 UK subjects and in a worldwide familial study of 66 kindreds. We found that the G1181 allele of TNFRSF11B, encoding lysine at codon 3 of the OPG protein, predisposes to both sporadic and familial PDB.

INTRODUCTION

Paget's disease of bone (PDB) is a common disorder characterized by focal abnormalities of bone turnover. Genetic factors are important in the pathogenesis of PDB, and studies have shown that inactivating mutations of the TNFRSF11B gene, encoding osteoprotegerin (OPG), cause the rare syndrome of juvenile Paget's disease. In this study, we sought to determine whether polymorphisms of the TNFRSF11B gene contribute to the pathogenesis of classical PDB.

MATERIALS AND METHODS

We screened for polymorphisms of the TNFRSF11B gene by DNA sequencing of the proximal promoter, coding exons, and intron-exon boundaries in 20 PDB patients and 10 controls. Informative single nucleotide polymorphisms (SNPs), including a G1181C SNP, which predicts a lysine-asparagine substitution at codon 3 of the OPG signal peptide and haplotypes, were related to the presence of PDB in 312 cases compared with 378 controls and to transmission of PDB in 140 affected offspring from 66 kindreds with familial PDB.

RESULTS AND CONCLUSIONS

The G1181 allele was significantly over-represented in PDB patients (chi(2) = 5.7, df = 1, p = 0.017, adjusted alpha = 0.024), equivalent to an odds ratio for PDB of 1.55 (95% CI: 1.11-2.16). The distribution of TNFRSF11B haplotypes significantly differed in sporadic PDB cases and controls (chi(2) = 30.2, df = 9, p < 0.001) because of over-representation of haplotypes containing the G1181 allele in cases. The family study showed that the most common haplotype containing the G1181 allele was transmitted more frequently than expected to 140 individuals with familial PDB (chi(2) = 7.35, df = 1, p < 0.01), and the transmission disequilibrium was even more pronounced in a subgroup of 78 familial PDB patients who did not carry mutations of the SQSTM1 gene (chi(2) = 8.44, df = 1, p < 0.005). We conclude that the G1181 allele of TNFRSF11B, encoding lysine at codon 3 of the OPG protein, predisposes to the development of sporadic PDB and familial PDB that is not caused by SQSTM1 mutations.

Identification of SQSTM1 mutations in familial Paget's disease in Australian pedigrees

We have conducted a genome-wide scan on a pedigree containing 372 adult members, of whom 49 have PDB. In the present study, we report linkage of a large pedigree to the PDB3 region on chromosome 5q35-qter with a peak multipoint LOD score of 6.77. Sequestosome 1 (SQSTM/p62) has been identified as the causative PDB gene in this region. Six sequestosome 1 mutations have been described to date. Four mutations have been identified in exon 8, 1210delT and 1215delC both resulting in premature stop codon at amino acid 394, 1215C to T (P392L), 1224insT (E396X), one mutation in exon 7, 1200C to T (P387L) and a G to A splice junction mutation at IVS7+1. These mutations cluster in the C terminus of the protein and are predicted to disrupt the ubiquitin binding properties of sequestosome 1. Sequence analysis of the gene encoding sequestosome 1 revealed a single base pair deletion (1215delC) segregating with the majority of affected members in the pedigree. This deletion introduces a stop codon at position 394, resulting in premature termination of the protein (L394X) and loss of the ubiquitin-associated binding domain. Screening of affected members from 10 further PDB families identified the previously reported P392L mutation in one family. No SQSTM1/p62 coding mutations were found in the remaining 9 families or in 113 age-matched controls.

Vitamin D receptor, oestrogen receptor- and calcium-sensing receptor genotypes, bone mineral density and biochemical markers in Paget's disease of bone

OBJECTIVES

The significance of genetic polymorphisms in the development of Paget's disease of bone is unclear at present.

METHODS

We analysed the BsmI polymorphism of the vitamin D receptor (VDR) gene, the PvuII and XbaI polymorphisms of the oestrogen receptor-alpha (ER alpha) gene, and the A986S polymorphism of the calcium-sensing receptor (CaSR) gene in 69 pagetic patients and 120 healthy subjects. We also examined the relationship of these polymorphisms with lumbar spine and femoral neck BMD as well as with biochemical parameters (serum alkaline phosphatase, osteocalcin and parathyroid hormone) in Paget's disease.

RESULTS

The XbaI and PvuII genotype distributions of the ER alpha gene were significantly different between patients with Paget's disease and control subjects (P<0.001). Also, the CaSR A986S genotype frequency was significantly different between pagetic patients and controls (P<0.01). No significant effect of gene polymorphisms on BMD or biochemical parameters of bone turnover was observed.

CONCLUSION

Our results suggest that the ER alpha PvuII/XbaI and CaSR A986S polymorphisms may contribute to genetic susceptibility to Paget's disease. However, further studies are required to investigate the underlying pathomechanism and to replicate the associations.

Paget's disease of bone in patients younger than 40 years

Paget's disease of bone, although common in the United States, is relatively rare in patients younger than 40 years. In a large archival series, 10% of patients with Paget's disease of bone were younger than 40 years. Pain followed by pathologic fracture was the most common presenting complaint in this group of patients. There was no gender difference comparing the younger group with the older group of patients. Of the 521 patients in this series, only 10 were African-American; the others were Caucasians. Seven African-American patients were in the group of patients who were younger than 40 years. Appendicular and monostotic bone involvement was more frequent in the younger age group although these differences were not statistically significant. The incidence of malignant transformation in pagetic bone was high (30.3%), and is a reflection of the high volume of uncommon tumor referrals to our consultation service. However, there were no cases of associated malignancies in the group of patients younger than 40 years.

Analysis of environmental factors in familial versus sporadic Paget's disease of bone--the New England Registry for Paget's Disease of Bone

A registry for Paget's Disease (PD) was created to study the environmental and familial features of this disorder. This study examines the first 202 people enrolled. Those with a family history of PD (20%) suffered earlier deformity and fracture, and tended to have grandparents born abroad. These findings suggest heritage is important in PD; the role of environment remains unclear.

INTRODUCTION

The New England Registry for Paget's Disease of Bone is a database that was created to explore the distribution and determinants of disease frequency.

METHODS

Using a case-series design, we explored the association of environmental factors in expression of the disease, comparing those patients with familial Paget's disease to those with sporadic Paget's disease (PD).

RESULTS AND CONCLUSIONS

Analysis of the first 202 patients enrolled in the registry revealed a positive family history (FH) in 41 (20%). Significant findings in this cohort included an earlier age of onset (51 years FH+ versus 59 years FH-, p < 0.05), a trend to a higher incidence of bone deformity (49% versus 33%, p < 0.1), and an increased fracture rate (27% versus 11%, p < 0.05). Persons with a FH of PD were less likely to record the United States or Canada as their grandparents' birthplace (p < 0.01), and sibships tended to be larger (p < 0.05). A history of measles infection, childhood exposure to pets, milk ingestion, year of immigration to the United States, birth order, level of education, and functional status did not distinguish the two groups. The database confirms the high prevalence of familial PD and supports the theory that heritable factors are important in the pathogenesis of this focal disorder of bone metabolism.

Bilateral enophthalmos associated with paget disease of the skull: a case report

PURPOSE

To describe a case of familial Paget disease of bone associated with bilateral enophthalmos and mild exposure keratopathy.

METHODS

Case report and literature review.

RESULTS

A 71-year-old woman with familial Paget disease of bone had a long history of "receding eyes," headaches, and moderately dry eyes. She had bilateral enophthalmos with mild exposure keratopathy. Radiologic and endocrinologic investigation confirmed Paget disease of bone affecting the skull.

CONCLUSIONS

Enophthalmos in association with Paget disease of bone is rare and is likely to result from differential expansion of the cranium compared with the orbital bones.

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.

Heterogeneity in familial dominant Paget disease of bone and muscular dystrophy

The combination of autosomal dominant, early onset Paget disease of bone (PDB) and muscular dystrophy is an unusual disorder. We recently mapped the disorder in a large family from central Illinois with PDB and proximal limb-girdle type of muscular dystrophy (LGMD), and in 3 additional families with hereditary inclusion body myopathy (HIBM), Paget disease of bone and frontotemporal dementia, to a unique locus on chromosome 9p21.1-q12. The present study describes an unrelated 10-member family with autosomal dominant PDB and a scapuloperoneal type of muscular dystrophy. Clinical, biochemical, and radiological evaluations were performed to delineate clinical features in this family. Progression of the muscular dystrophy begins with weakness in the distal muscles of the legs accompanied by foot drop. EMG and muscle biopsy are compatible with a primary dystrophy. Onset of Paget disease is early, at a mean age of 41 years, with initial distribution in the long bones and eventual infiltration of the spine and pelvis. Creatine phosphokinase (CPK) and alkaline phosphatase levels are elevated in affected individuals. Molecular analyses excluded all known loci for Paget disease of bone, scapuloperoneal muscular dystrophy (SPMD), fascioscapulohumeral muscular dystrophy (FSH), amyotrophic lateral sclerosis (ALS), Bethlem myopathy, two forms of autosomal dominant limb-girdle muscular dystrophy (LGMD), and the critical region for LGMD or HIBM/PDB on chromosome 9p21.1-q12, thus providing evidence for genetic heterogeneity among families with the unique combination of muscular dystrophy and Paget disease of bone.