Clinical practice. Paget's disease of bone

ZNF687 mutations are frequently found in pagetic patients from South Italy: implication in the pathogenesis of Paget's disease of bone

Paget's disease of bone (PDB) is a skeletal disorder whose molecular basis is not fully elucidated. However, 10% of patients show a familial PDB and 35% of them carry mutations in the SQSTM1 gene. We recently reported a founder mutation (p.Pro937Arg) in the ZNF687 gene, underlying PDB complicated by giant cell tumor (GCT/PDB) and rarely occurring in PDB patients without neoplastic degeneration. Since 80% of Italian GCT/PDB patients derive from Avellino, we hypothesized that ZNF687 mutation rate was higher in this region than elsewhere. Interestingly, our molecular analysis on 30 PDB patients showed that 33% hosted ZNF687 mutations, with the p.Pro937Arg identified in 8 familial cases. Two novel ZNF687 mutations (p.Pro665Leu and p.Gln784Glu) were detected in 2 sporadic patients. Only 2 subjects were positive for the p.Pro392Leu mutation in SQSTM1. ZNF687-mutated patients showed a severe PDB, with a remarkable number of affected sites. in vitro studies revealed that the ZNF687-mutant osteoclasts appeared as giant sized with up to 150 nuclei, never described in PDB. Finally, we also confirmed the causality of the p.Pro937Arg mutation in 4 additional GCT/PDB cases deriving from the same geographic area, indicating that PDB and GCT/PDB represent 2 sides of the same coin.

Skeletal dissemination in Paget's disease of the spine

PURPOSE

Paget's disease of bone (PDB) is a common skeletal disorder that is associated with locally increased bone turnover, skeletal deformity and pain. We report a case of skeletal dissemination in PDB of the spine.

METHODS

Case report.

RESULTS

A 46-year-old former professional athlete suffered from disseminated PDB throughout the spine and hips after various surgical interventions including spondylodesis, bone grafting and bone morphogenetic protein (rhBMP-2) administration. Only intravenous zoledronic acid prevented the further progression of skeletal dissemination, which was expressed by a normalization of (bone-specific) alkaline phosphatase levels. The biopsy obtained from the lumbar spine confirmed the diagnosis of PDB in the absence of malignant transformation.

CONCLUSIONS

We outline skeletal dissemination as a possibly surgery-related complication in a patient with PDB in the lumbar spine. Bisphosphonates remain the treatment of first choice in PDB and surgical interventions should be considered very carefully.

Bisphosphonates for Paget's disease of bone in adults

BACKGROUND

Bisphosphonates are considered to be the treatment of choice for people with Paget's disease of bone. However, the effects of bisphosphonates on patient-centred outcomes have not been extensively studied. There are insufficient data to determine whether reducing and maintaining biochemical markers of bone turnover to within the normal range improves quality of life and reduces the risk of complications.

OBJECTIVES

To assess the benefits and harms of bisphosphonates for adult patients with Paget's disease of bone.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, ISI Web of Knowledge and trials registers up to March 2017. We searched regulatory agency published information for rare adverse events.

SELECTION CRITERIA

Randomised controlled trials (RCTs) of bisphosphonates as treatment for Paget's disease in adults.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened search results, extracted data and assessed studies for risk of bias. We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

We included 20 trials (25 reports, 3168 participants). Of these, 10 trials (801 participants) compared bisphosphonates (etidronate, tiludronate, ibandronate, pamidronate, olpadronate, alendronate, risedronate, zoledronate) versus placebo, seven compared two bisphosphonates (992 participants), one trial compared a bisphosphonates with a bisphosphonate plus calcitonin (44 participants), and two studies, the largest trial (1331 participants) and its interventional extension study (502 participants), compared symptomatic treatment and intensive treatment where the goal was to normalise alkaline phosphatase.Most studies were assessed at low or unclear risk of bias. Six of 10 studies comparing bisphosphonates versus placebo were assessed at high risk of bias, mainly around incomplete outcome data and selective outcome reporting.Participant populations were reasonably homogeneous in terms of age (mean age 66 to 74 years) and sex (51% to 74% male). Most studies included participants who had elevated alkaline phosphatase levels whether or not bone pain was present. Mean follow-up was six months.Bisphosphonates versus placeboBisphosphonates tripled the proportion (31% versus 9%) of participants whose bone pain disappeared (RR 3.42, 95% confidence interval (CI) 1.31 to 8.90; 2 studies, 205 participants; NNT 5, 95% CI 1 to 31; moderate-quality evidence). This result is clinically important. Data were consistent when pain change was measured as any reduction (RR 1.97, 95% CI 1.29 to 3.01; 7 studies, 481 participants).There was uncertainty about differences in incident fractures: 1.4% fractures occurred in the bisphosphonates group and none in the placebo group (RR 0.89, 95% CI 0.18 to 4.31; 4 studies, 356 participants; very low-quality evidence).None of the studies reported data on orthopaedic surgery, quality of life or hearing thresholds.Results regarding adverse effects and treatment discontinuation were uncertain. There was a 64% risk of mild gastrointestinal adverse events in intervention group participants and 48% in the control group (RR 1.32, 95% CI 0.91 to 1.92; 6 studies, 376 participants; low-quality evidence). The likelihood of study participants discontinuing due to adverse effects was slightly higher in intervention group participants (4.4%) than the control group (4.1%) (RR 1.01, 95% CI 0.41 to 2.52; 6 studies, 517 participants; low-quality evidence). Zoledronate was associated with an increased risk of transient fever or fatigue (RR 2.57, 95% CI 1.21 to 5.44; 1 study, 176 participants; moderate-quality evidence).Bisphosphonates versus active comparatorMore participants reported pain relief with zoledronate than pamidronate (RR 1.30, 95% CI 1.10 to 1.53; 1 study, 89 participants; NNT 5, 95% CI 3 to 11) or risedronate (RR 1.36, 95% CI 1.06 to 1.74; 1 study, 347 participants; NNT 7, 95% CI 4 to 24; very low quality evidence). This result is clinically important.There was insufficient evidence to confirm or exclude differences in adverse effects of bisphosphonates (RR 1.05, 95% CI 0.95 to 1.76; 2 studies, 437 participants; low-quality evidence) and treatment discontinuation (2 studies, 437 participants) (RR 2.04, 95% CI 0.43 to 9.59; 2 studies, 437 participants; very low-quality evidence).Intensive versus symptomatic treatmentThere was no consistent evidence of difference to response in bone pain, bodily pain or quality of life in participants who received intensive versus symptomatic treatment.Inconclusive results were observed regarding fractures and orthopaedic procedures for intensive versus symptomatic treatment (intensive treatment for fracture: RR 1.84, 95% CI 0.76 to 4.44; absolute risk 8.1% versus 5.2%; orthopaedic procedures: RR 1.58, 95% CI 0.80 to 3.11; absolute risk 5.6% versus 3.0%; 1 study, 502 participants; low-quality evidence).There was insufficient evidence to confirm or exclude an important difference in adverse effects between intensive and symptomatic treatment (RR 1.05, 95% CI 0.79 to 1.41; low-quality evidence).There was insufficient evidence to confirm or exclude an important difference of risk of rare adverse events (including osteonecrosis of the jaw) from the regulatory agencies databases.

AUTHORS' CONCLUSIONS

We found moderate-quality evidence that bisphosphonates improved pain in people with Paget's disease of bone when compared with placebo. We are uncertain about the results of head-to-head studies investigating bisphosphonates. We found insufficient evidence of benefit in terms of pain or quality of life from intensive treatment. Information about adverse effects was limited, but serious side effects were rare, and rate of withdrawals due to side effects was low.

Familial Early-Onset Paget's Disease of Bone Associated with a Novel hnRNPA2B1 Mutation

Paget disease of bone (PDB) is a common metabolic bone disease characterized by increased bone resorption and disorganized bone formation which affect single or multiple sites of bones. Although the exact cause of PDB is still controversial, genetic factors are considered to play an important role in PDB. Several genes involved in the differentiation or function of osteoclast were shown to be associated with PDB or related syndrome such as SQSTM1, TNFRSF11A, TNFRSF11B, and ZNF687. Multisystem proteinopathy (MSP), a newly proposed syndrome including inclusion body myopathy (IBM), PDB, frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS), is mainly caused by mutation in VCP gene. In 2013, a new casual gene for MSP was identified as hnRNPA2B1 gene. This may partly account for the inherited PDB traits which is however negative for mutation in already known causative PDB genes. We investigated a Chinese family with multiple affected individuals with PDB, but none of the members showed symptoms of IBM, FTD, or ALS. Three patients were evaluated clinically, biochemically, and radiographically. To screen for the responsible mutation, whole-exome sequencing was conducted in the proband, another patient, as well as a normal individual from the family. This revealed a novel heterozygous missense mutation of hnRNPA2B1 gene (c.929C>T, p. P310L) in the two patients which was then verified in all affected individuals. We describe here a novel missense mutation in hnRNPA2B1 gene in a large pedigree affected with PDB with members who do not present other manifestations of multisystem proteinopathy, such as IBM, FTD, and ALS.

Antibody Response to Paramyxoviruses in Paget's Disease of Bone

Paget's disease of bone (PDB) is a common skeletal disorder characterised by focal abnormalities of increased and disorganised bone turnover. Genetic factors play a central role in the pathogenesis of PDB but environmental factors also contribute. Measles virus (MV), respiratory syncytial virus (RSV) and canine distemper virus (CDV) have all been implicated as potential disease triggers but the data are conflicting. Since chronic paramyxovirus infection with measles is known to be accompanied by increased production of antiviral antibodies, we have analysed circulating concentrations of antibodies to MV, CDV, and RSV as well as mumps, rubella and varicella zoster virus (VZV) in 463 patients with PDB and 220 aged and gender-matched controls. We also studied the relation between viral antibody concentrations and various markers of disease severity and extent in 460 PDB patients. A high proportion of cases and controls tested positive for antiviral antibodies but there was no significant difference in circulating antibody concentrations between PDB cases and controls for MV, CDV, RSV, rubella or VZV. However, mumps virus antibody levels were significantly higher in the PDB cases (mean ± SD = 3.1 ± 0.84 vs. 2.62 ± 0.86. p < 0.001). There was no association between disease severity and circulating antibody concentrations to any of the viruses. In conclusion, we found no evidence to suggest that PDB is associated with abnormalities of immune response to measles or other paramyxoviruses, although there was evidence of a greater antibody response to mumps. The results do not support that hypothesis that PDB is associated with a persistent infection with measles or other paramyxoviruses.

[Paget's disease of bone: Diagnostic and therapeutic updates]

Paget's disease of bone is the second most common metabolic bone disease after osteoporosis. Its pathogenesis is not yet clearly understood. Geographic distribution and epidemiological variations suggest a role of genetic and environmental factors in its pathophysiology. The frequency of the Paget's disease of bone increases with age. Its discovery can be fortuitous. Prognosis mainly depends on the occurrence of complications involving bones and joints, neurological, cardiovascular or metabolic systems. Treatment of symptomatic forms currently relies on bisphosphonates that have transformed its prognosis.

The distinct clinical features of giant cell tumor of bone in pagetic and non-pagetic patients are associated with genetic, biochemical and histological differences

Giant Cell Tumor of Bone (GCT) is a tumor characterized by neoplastic mesenchymal stromal cells and a high number of osteoclast-like multinucleated giant cells. Rarely, GCT could arise in bones affected by Paget's disease of bone (GCT/PDB). Although it is already known that GCT/PDB and GCT show a different clinical profile regarding the age-onset and skeletal localization, our deep clinical comparison between the two GCT/PDB and GCT cohorts, permitted us to identify additional differences (e.g. focality, ALP serum levels, the 5-year survival rate and the familial recurrence), strongly suggesting a different molecular basis. Accordingly, driver somatic mutations in H3F3A and IDH2 were described in GCT patients, while we recently identified a germline mutation in ZNF687 as the genetic defect of GCT/PDB patients. Here, we detected H3F3A mutations in our GCT cohort, confirming its molecular screening as the elected diagnostic tool, and then we excluded the two-hit in H3F3A and IDH2 as the trigger event for the GCT/PDB development. Importantly, we also identified an alternative biochemical profile with GCT/PDB not exhibiting the up-regulation of the GCT marker FGFR2IIIc. Finally, our histological analysis also showed a different appearance of the two forms of the tumor, with GCT/PDB showing a higher number of osteoclast-like giant cells (twice), with an abnormal number of nuclei per cell, corroborating its different behaviour in terms of neoplastic properties. We demonstrated that the distinct clinical features of pagetic and conventional GCT are associated with different genetic background, resulting in a specific biochemical and histological behaviour of the tumour.

Long-Term Randomized Trial of Intensive Versus Symptomatic Management in Paget's Disease of Bone: The PRISM-EZ Study

It has been suggested that normalization of bone turnover may improve clinical outcome in Paget's disease of bone (PDB) by preventing complications such as fractures and the development of osteoarthritis. Here we investigated the long-term effects of a treatment strategy that aimed to normalize bone turnover in PDB with that of symptomatic treatment. The study group comprised 502 subjects who were enrolled into a 3-year extension of the Paget's Disease: Randomized Trial of Intensive versus Symptomatic Management (PRISM) study. Intensive bisphosphonate therapy was continued in 270 of these subjects with the aim of normalizing bone turnover using zoledronic acid as the treatment of first choice. Symptomatic treatment continued in 232 subjects in whom bisphosphonates were only given for the treatment of bone pain. The primary outcome was fracture and secondary outcomes were orthopedic procedures, quality of life, and bone pain, adjusted for baseline characteristics. Serum total alkaline phosphatase (ALP) concentrations were significantly lower in the intensive group on entry to the study and the differences between groups increased as the study progressed. There were no clinically important differences in quality of life measures or bone pain between the treatment groups. Intensive treatment was associated with a nonsignificant increase in fracture risk (hazard ratio = 1.90; 95% CI, 0.91 to 3.98; p = 0.087), orthopedic procedures (1.81; 95% CI, 0.71 to 4.61; p = 0.214), and serious adverse events (relative risk 1.28; 95% CI, 0.96 to 1.42). We conclude that long-term intensive bisphosphonate therapy confers no clinical benefit over symptomatic therapy and is associated with a nonsignificant increase in the risk of fractures, orthopedic events, and serious adverse events. The results of this study suggest that in patients with established PDB, bisphosphonate therapy should focus on control of symptoms rather than suppression of bone turnover. © 2016 American Society for Bone and Mineral Research.

Management of Paget's Disease of the Calcaneum

The calcaneum is not the most common site for Paget's disease of bone, with only a few reports of monostotic involvement. We present 2 cases of Paget's disease of bone affecting the calcaneus, present an overview of the published data, and describe our management of these interesting cases.

Atlas of human diseases influenced by genetic variants with extreme allele frequency differences

Genetic variants with extreme allele frequency differences (EAFD) may underlie some human health disparities across populations. To identify EAFD loci, we systematically analyzed and characterized 81 million genomic variants from 2504 unrelated individuals of 26 world populations (phase III of the 1000 Genomes Project). Our analyses revealed a total of 434 genes, 15 pathways, and 18 diseases and traits influenced by EAFD variants from five continental populations. They included known EAFD genes, such as LCT (lactose tolerance), SLC24A5 (skin pigmentation), and EDAR (hair morphology). We found many novel EAFD genes, including TBC1D2B (autophagy mediator), TRIM40 (gastrointestinal inflammatory regulator), KRT71, KRT75, KRT83, and KRTAP10-1 (hair and epithelial keratin synthesis), PIK3R3 (insulin receptor interaction), DARS (neurological disorders), and NACA2 (skin inflammatory response). Our results also showed four complex diseases significantly associated with EAFD loci, including asthma (adjusted enrichment P = 4 × 10^-8), type I diabetes (P = 6 × 10^-9), alcohol consumption (P = 0.0002), and attention deficit/hyperactivity disorder (P = 0.003). This study provides a comprehensive atlas of genes, pathways, and human diseases significantly influenced by EAFD variants.

Genetic factors influencing the risk of multiple myeloma bone disease

A major complication of multiple myeloma (MM) is the development of osteolytic lesions, fractures and bone pain. To identify genetic variants influencing the development of MM bone disease (MBD), we analyzed MM patients of European ancestry (totaling 3774), which had been radiologically surveyed for MBD. Each patient had been genotyped for ~6 00 000 single-nucleotide polymorphisms with genotypes for six million common variants imputed using 1000 Genomes Project and UK10K as reference. We identified a locus at 8q24.12 for MBD (rs4407910, OPG/TNFRSF11B, odds ratio=1.38, P=4.09 × 10(-9)) and a promising association at 19q13.43 (rs74676832, odds ratio=1.97, P=9.33 × 10(-7)). Our findings demonstrate that germline variation influences MBD and highlights the importance of RANK/RANKL/OPG pathway in MBD development. These findings will contribute to the development of future strategies for prevention of MBD in the early precancerous phases of MM.

Development of a molecular test of Paget's disease of bone

Depending on populations, 15 to 40% of patients have a familial form of Paget's disease of bone (PDB), which is transmitted in an autosomal-dominant mode of inheritance with incomplete penetrance. To date, only SQSTM1 gene mutations have been linked to the disease. Several single nucleotide polymorphisms (SNPs) have been associated with PDB in patient non-carriers of SQSTM1 mutations, but they have minor size effects. The current clinical practice guidelines still recommend to measure total serum alkaline phosphatase (sALP) for PDB screening. However, genetic or bone biomarkers alone may lack sensitivity to detect PDB. Thus, the objective of this study was to develop a molecular test of PDB, combining genetic and bone biomarkers, in order to detect PDB, which is frequently asymptomatic. We genotyped 35 SNPs previously associated with PDB in 305 patients, and 292 healthy controls. In addition, serum levels of 14 bone biomarkers were assayed in 51 patients and 151 healthy controls. Bivariate and multivariate logistic regression models with adjustment for age and sex were fitted to search for a combination of SNPs and/or bone biomarkers that could best detect PDB in patient non-carriers of SQSTM1 mutations. First, a combination of five genetic markers gave rise to the highest area under the ROC curve (AUC) with 95% confidence interval [95% CI] of 0.731 [0.688; 0.773], which allowed us to detect 81.5% of patients with PDB. Second, a combination of two bone biomarkers had an AUC of 0.822 [0.726; 0.918], and was present in 81.5% of patients with PDB. Then, the combination of the five genetic markers and the two bone biomarkers increased the AUC up to 0.892 [0.833; 0.951], and detected 88.5% of patients with PDB. These results suggested that an algorithm integrating first a screen for SQSTM1 gene mutations, followed by either a genetic markers combination or a combined genetic and biochemical markers test in patients non-carrier of any SQSTM1 mutation, may detect the PDB phenotype better than biomarkers already available in the clinical practice.

Two diagnoses from bone marrow biopsy: multiple myeloma and Paget's disease of bone

Multiple myeloma and Paget's disease of bone show certain similarities such as increased osteoclastic activity and predilection to the axial skeleton. However, pathological and radiological changes of the bones are distinctive between multiple myeloma and Paget's disease of bone. This case report describes a patient who had a concomitant diagnosis of multiple myeloma and Paget's disease evidenced from bone marrow biopsy. Such a co-existence is rare, with only a few cases reported so far.

ZNF687 Mutations in Severe Paget Disease of Bone Associated with Giant Cell Tumor

Paget disease of bone (PDB) is a skeletal disorder characterized by focal abnormalities of bone remodeling, which result in enlarged and deformed bones in one or more regions of the skeleton. In some cases, the pagetic tissue undergoes neoplastic transformation, resulting in osteosarcoma and, less frequently, in giant cell tumor of bone (GCT). We performed whole-exome sequencing in a large family with 14 PDB-affected members, four of whom developed GCT at multiple pagetic skeletal sites, and we identified the c.2810C>G (p.Pro937Arg) missense mutation in the zinc finger protein 687 gene (ZNF687). The mutation precisely co-segregated with the clinical phenotype in all affected family members. The sequencing of seven unrelated individuals with GCT associated with PDB (GCT/PDB) identified the same mutation in all individuals, unravelling a founder effect. ZNF687 is highly expressed during osteoclastogenesis and osteoblastogenesis and is dramatically upregulated in the tumor tissue of individuals with GCT/PDB. Interestingly, our preliminary findings showed that ZNF687, indicated as a target gene of the NFkB transcription factor by ChIP-seq analysis, is also upregulated in the peripheral blood of PDB-affected individuals with (n = 5) or without (n = 6) mutations in SQSTM1, encouraging additional studies to investigate its potential role as a biomarker of PDB risk.

Effect of zoledronic acid on serum calcium in Paget's disease patients after educational strategies to improve calcium and vitamin D supplementation

OBJECTIVE

Bisphosphonates are the most effective therapeutic agents in patients with Paget's disease of bone. As a result of their inhibition of osteoclastic activity, hypocalcemia of variable frequency and severity following intravenous bisphosphonate therapy has been reported. The present study assessed the effect of physician and patient education on adequate supplementation of calcium and vitamin D to reduce the potential risk of developing hypocalcemia following infusion of 5 mg zoledronic acid.

METHODS

This was an open-label, multicenter, controlled registry trial in which patients with Paget's disease were treated with a single intravenous infusion of zoledronic acid. Physicians were provided with educational materials focusing on optimization of calcium and vitamin D supplementation following zoledronic infusion that they used to educate their patients. The primary safety variable was the percentage of patients with serum calcium level <2.07mmol/l 9-11 days after zoledronic acid infusion.

RESULTS

A total of 75 patients were evaluable in the post dose hypocalcemia safety analysis. Of these, only 1 patient had treatment-emergent hypocalcemia, with a serum calcium level of 1.92 mmol/l 4 days following therapy. Hypocalcemia-related symptoms were not reported in this patient and the serum calcium returned to normal range at 2.17 mmol/l within 1 week on oral calcium supplementation.

CONCLUSIONS

These results suggest that, with optimization of calcium and vitamin D supplementation by physician and patient education, hypocalcemia is an infrequent occurrence following zoledronic acid infusion.

Paget's sarcoma of the patella

Paget's sarcoma is a rare complication of Paget's disease and isolated Paget's disease of the patella is extremely rare. We describe a unique case of Paget's sarcoma of the patella in a 69-year-old male farmer who had a remote history of a fracture in the same patella 40 years previously. In this case, imaging and pathogenesis of Paget's disease of bone is described and factors implicated in the development of Paget's disease in this patient are evaluated.

Bone turnover markers in Paget's disease of the bone: A Systematic review and meta-analysis

The aim of this systematic review and meta-analysis is to study the utility of the commonly used bone turnover markers in evaluating disease activity in patients with Paget's disease of bone before and after treatment with bisphosphonates. We found good correlation between the bone turnover marker concentrations and disease activity assessed by bone scintigraphy.

INTRODUCTION

Paget's disease of bone is a common skeletal disorder of the elderly. Bone turnover marker concentrations are used for diagnosis and follow-up. We aimed to compare the available bone turnover markers and determine their utility in assessing disease activity when compared to quantitative bone scintigraphy.

METHODS

We conducted a systematic review and meta-analysis searching MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and Scopus. We evaluated total alkaline phosphatase (total ALP), bone-specific alkaline phosphatase (bone ALP), procollagen type 1 amino-terminal propeptide (P1NP), serum, and urine C-terminal telopeptide (uCTx and sCTx, respectively), and urine N-terminal telopeptide (uNTx). The main outcome of interest was the correlation of disease activity with concentrations of bone turnover markers in Paget's disease patients before and after treatment with bisphosphonates. Correlation coefficients were pooled across studies using the random effects model.

RESULTS

We included 17 observational studies and one trial reporting on 953 patients. Prior to treatment, all studied bone turnover markers had moderate to strong correlation with scintigraphic indices (correlation coefficients ranging from 0.58 to 0.80) with no statistically significant difference between the bone turnover markers overall (p = 0.08). P1NP, uNTx, and bone ALP tend to have higher correlation with scintigraphy. After starting treatment with bisphosphonate, there was moderate to strong correlation with disease activity with all markers except bone ALP (correlation coefficients ranging from 0.43 to 0.70).

CONCLUSION

The findings of this meta-analysis suggest the Paget's disease activity is best monitored by following P1NP levels. However, total ALP, bone ALP, and uNTx are good alternatives as markers of disease activity in untreated patients. Total ALP and uNTx can be useful in following patients with Paget's disease after treatment if P1NP is not available. Clinicians, however, should take availability, cost, and the presence of liver disease into consideration when deciding which bone turnover marker is most appropriate when evaluating patients with Paget's disease.

Targeted sequencing of the Paget's disease associated 14q32 locus identifies several missense coding variants in RIN3 that predispose to Paget's disease of bone

Paget's disease of bone (PDB) is a common disorder with a strong genetic component characterized by increased but disorganized bone remodelling. Previous genome-wide association studies identified a locus on chromosome 14q32 tagged by rs10498635 which was significantly associated with susceptibility to PDB in several European populations. Here we conducted fine-mapping and targeted sequencing of the candidate locus to identify possible functional variants. Imputation in 741 PDB patients and 2699 controls confirmed that the association was confined to a 60 kb region in the RIN3 gene and conditional analysis adjusting for rs10498635 identified no new independent signals. Sequencing of the RIN3 gene identified a common missense variant (p.R279C) that was strongly associated with the disease (OR = 0.64; P = 1.4 × 10⁻⁹), and was in strong linkage disequilibrium with rs10498635. A further 13 rare missense variants were identified, seven of which were novel and detected only in PDB cases. When combined, these rare variants were over-represented in cases compared with controls (OR = 3.72; P = 8.9 × 10⁻¹⁰). Most rare variants were located in a region that encodes a proline-rich, intrinsically disordered domain of the protein and many were predicted to be pathogenic. RIN3 was expressed in bone tissue and its expression level was ∼10-fold higher in osteoclasts compared with osteoblasts. We conclude that susceptibility to PDB at the 14q32 locus is mediated by a combination of common and rare coding variants in RIN3 and suggest that RIN3 may contribute to PDB susceptibility by affecting osteoclast function.

Modifications to nano- and microstructural quality and the effects on mechanical integrity in Paget's disease of bone

Paget's disease of bone (PDB) is the second most common bone disease mostly developing after 50 years of age at one or more localized skeletal sites; it is associated with severely high bone turnover, bone enlargement, bowing/deformity, cracking, and pain. Here, to specifically address the origins of the deteriorated mechanical integrity, we use a cohort of control and PDB human biopsies to investigate multiscale architectural and compositional modifications to the bone structure (ie, bone quality) and relate these changes to mechanical property measurements to provide further insight into the clinical manifestations (ie, deformities and bowing) and fracture risk caused by PDB. Here, at the level of the collagen and mineral (ie, nanometer-length scale), we find a 19% lower mineral content and lower carbonate-to-phosphate ratio in PDB, which accounts for the 14% lower stiffness and 19% lower hardness promoting plastic deformation in pathological bone. At the microstructural scale, trabecular regions are known to become densified, whereas cortical bone loses its characteristic parallel-aligned osteonal pattern, which is replaced with a mosaic of lamellar and woven bone. Although we find this loss of anisotropic alignment produces a straighter crack path in mechanically-loaded PDB cases, cortical fracture toughness appears to be maintained due to increased plastic deformation. Clearly, the altered quality of the bone structure in PDB affects the mechanical integrity leading to complications such as bowing, deformities, and stable cracks called fissure fractures associated with this disease. Although the lower mineralization and loss of aligned Haversian structures do produce a lower modulus tissue, which is susceptible to deformities, our results indicate that the higher levels of plasticity may compensate for the lost microstructural features and maintain the resistance to crack growth.

Clinical characteristics and evolution of giant cell tumor occurring in Paget's disease of bone

Patients with Paget's bone disease (PDB) have an increased risk of developing giant cell tumor (GCT). This study was performed to evaluate the clinical characteristics and evolution of GCT complicating PDB and to compare these clinical characteristics to those observed in two large PDB cohorts, the PDB Italian Registry and the United Kingdom's Multi-Centre Randomised Controlled Trial of Symptomatic Versus Intensive Bisphosphonate Therapy for Paget's Disease (PRISM) study. A systematic literature review identified 117 cases of PDB complicated by GCT (PDB-GCT), which involved the skeletal sites affected by PDB (110 patients) or the extraskeletal tissues adjacent to affected bones (7 patients). In contrast to what previously reported for GCT patients without GCT patients (83.2%) were white and one-fourth of them (24.8%) had multifocal GCTs. Compared to PDB patients without GCT, PDB-GCT patients showed a higher male/female ratio (2.1 versus 1.2) and more severe disease (age at PDB onset 52.1 ± 12.1 versus 63.3 ± 10.6 years; number of affected sites 6.1 ± 2.9 versus 2.34 ± 1.6; prevalence of polyostotic PDB 93.3% versus 60.6%). The mortality rate of PDB-GCT patients was higher than those occurring in GCT patients without PDB (about 50% versus 0% to 5% at 5 years) or in PDB patients without GCT (log rank = 29.002). Moreover, up to 98% of PDB-GCT cases had elevated total alkaline phosphatase levels at neoplasm diagnosis, suggestive of active PDB. Importantly, PDB-GCT patients from Southern Italy (45.6% of all GCT patients) showed a higher prevalence of multifocal GCT (51.7%) and of positive familial history for PDB (70.8%) and GCT (65.0%). Finally, indirect evidence suggests a decline in the incidence of GCT in PDB patients. The occurrence of GCT in PDB patients is associated with severe disease and reduced life expectancy of affected patients. The increased prevalence of familial diseases in PDB-GCT patients from Southern Italy suggests a founder effect. The observed changes over time in the incidence of GCT in PDB patients could be related to improved clinical management and/or living conditions of patients.

Paget's Disease of Bone among Various Ethnic Groups

Paget's disease of bone (PDB) is a relatively benign disease common among many European populations, including those in the UK, Italy and Spain. However, it appears to be rare among Scandinavians and non-European immigrants living in Europe. The prevalence among Asian populations may be underestimated because a large number of reported cases were discovered incidentally. There is a need for surveys addressing the prevalence rate and consequences of PDB to be carried out in various parts of the world, particularly Asia.

Current perspectives on bisphosphonate treatment in Paget's disease of bone

Paget's disease of bone is a chronic metabolic bone disease with focal increase in bone turnover. The exact etiology of the disease is uncertain, although genetic and environmental factors are believed to be important. Bisphosphonate is the main class of medication being used to control disease activity via its antiresorptive effect. This review discusses the controversies concerning the use of bisphosphonates in the treatment of Paget's disease of bone, the efficacy of different bisphosphonates in controlling disease activity, and the possible rare side effects of bisphosphonates. Symptoms are the main indication for treatment in Paget's disease of bone. As treatment benefits in asymptomatic individuals remain controversial and nonevidence based, the decision to treat these patients should be individualized to their risk and benefit profiles. There are several trials conducted to evaluate and compare the efficacy of different regimes of bisphosphonates for treating Paget's disease of bone. Most trials used biochemical markers rather than clinical symptoms or outcomes as parameters for comparison. Zoledronate is an attractive option as it can achieve high rates of biochemical remission and sustain long duration of suppression by a single dose. Atypical femoral fracture and osteonecrosis of the jaw are two rare and severe side effects reported, possibly related to the use of bisphosphonates in patients with osteoporosis and malignancy-induced hypercalcemia. As the regimes of bisphosphonates used for treating Paget's disease of bone are different from those two diseases, the risks of developing these two possible side effects are expected to be very low, although this remains unknown. Vitamin D and calcium supplement should be given to patients at risk of vitamin D insufficiency when given zoledronate, as symptomatic hypocalcemia may develop. For those intolerant of bisphosphonates, subcutaneous calcitonin can be used for a limited period due to its associated risk of malignancy.

Global gene expression profiling in R155H knock-in murine model of VCP disease

Dominant mutations in the valosin-containing protein (VCP) gene cause inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia, which is characterized by progressive muscle weakness, dysfunction in bone remodeling, and frontotemporal dementia. More recently, VCP has been linked to 2% of familial amyotrophic lateral sclerosis cases. VCP plays a significant role in a plethora of cellular functions including membrane fusion, transcription activation, nuclear envelope reconstruction, postmitotic organelle reassembly, and cell cycle control. To elucidate the pathological mechanisms underlying the VCP disease progression, we have previously generated a VCP(R155H/+) mouse model with the R155H mutation. Histological analyses of mutant muscle showed vacuolization of myofibrils, centrally located nuclei, and disorganized muscle fibers. Global expression profiling of VCP(R155H/+) mice using gene annotations by DAVID identified key dysregulated signaling pathways including genes involved in the physiological system development and function, diseases and disorders, and molecular and cellular functions. There were a total of 212 significantly dysregulated genes, several of which are involved in the regulation of proteasomal function and NF-κB signaling cascade. Findings of the gene expression study were validated by using quantitative reverse transcriptase polymerase chain reaction analyses to test genes involved in various signaling cascades. This investigation reveals the importance of the VCP(R155H/+) mouse model in the understanding of cellular and molecular mechanisms causing VCP-associated neurodegenerative diseases and in the discovery of novel therapeutic advancements and strategies for patients suffering with these debilitating disorders.

Clinical presentation of Paget's disease: evaluation of a contemporary cohort and systematic review

Paget's disease of bone (PDB) has become less common over recent decades but it is unclear if this has impacted on clinical presentation. Here we evaluated the presenting features of PDB in a contemporary cohort of UK patients and conducted a systematic review of studies in which the presenting features had been reported. The case series comprised 88 patients referred to a specialist clinic between 2005 and 2013. Bone pain was the most common presenting feature occurring in 73.8% of patients. Others included bone deformity (18.1%), deafness (7.9%) and pathological fracture (5.7%). The disease was asymptomatic in 22% of cases. Antiresorptive treatment was given for pain in 34 cases and 61.7% of patients responded. Patients with a shorter disease duration were more likely to respond (p = 0.047). In the systematic review, bone pain was the most common presenting feature (52.2% of cases) followed by deformity (21.5%), deafness (8.9%) and fracture (8.5%). Time trend analysis in subjects of European descent showed that fracture was less common in studies performed during the past 25 years as compared with older studies (5.5 vs. 10.8% p < 0.001) whereas pain was more common (54.3 vs. 48.3%, p = 0.003). While changes in the mode of presentation of PDB have occurred over recent years, many patients present with complications such as fracture and deformity. Further research is required to determine if early detection and therapeutic intervention might be of value in preventing the morbidity associated with this common disease.

Genetics of Paget's disease of bone

Paget's disease of bone (PDB) is a common condition, which is characterised by focal areas of increased and disorganized bone remodeling. Genetic factors play an important role in the disease. In some cases, Paget's disease is inherited in an autosomal dominant manner and the most common cause for this is a mutation in the SQSTM1 gene. Other familial cases have been linked to the OPTN locus on Chromosome 10p13 and still other variants have been identified by genome wide association studies that lie within or close to genes that play roles in osteoclast differentiation and function. Mutations in TNFRSF11A, TNFRSF11B and VCP have been identified in rare syndromes with PDB-like features. These advances have improved understanding of bone biology and the causes of PDB. The identification of genetic markers for PDB also raises the prospect that genetic profiling could identify patients at high risk of developing complications, permitting enhanced surveillance and early therapeutic intervention.

Five polyostotic conditions that general orthopedic surgeons should recognize (or should not miss)

General orthopedic surgeons frequently encounter patients with conditions affecting multiple bones. It is important to recognize common polyostotic diseases. This article describes five polyostotic conditions: Multipe Enchondromatosis (Ollier Disease and Maffucci syndrome), Multiple Hereditary Exostosis (Diaphyseal Aclasis), Fibrous Dysplasia (McCune-Albright syndrome and Mazabraud syndrome), Paget's Disease of bone (Osteitis Deformans), and Skeletal Metastases. This is a survey of the clinical, pathologic and radiographic features that assist in diagnosing these conditions. Also, an overview of the laboratory findings, treatment, follow-up, and prognosis is presented. Recognizing these diseases will aid in prompt and accurate diagnosis and appropriate referral and therapy.

An Insight in to Paget's Disease of Bone

Paget's disease of bone (PDB) is a common disorder which may affect one or many bones. Although many patients are asymptomatic, a variety of symptoms and complications may occur. PDB is a focal disorder of bone turnover characterized by excessive bone resorption coupled with bone formation. PDB begins with a period of increased osteoclastic activity and bone resorption, followed by increased osteoblast production of woven bone that is poorly mineralized. In the final phase of the disease process, dense cortical and trabecular bone deposition predominates, but the bone is sclerotic and poorly organized and lacks the structural integrity and strength of normal bone. This article briefly reviews the etiopathogenesis, clinical radiographic and histological features of Paget's disease.

Republished: Paget's disease of bone: clinical review and update

Paget's disease (PD) is a focal disorder of bone remodelling that occurs commonly in older people. In this article, we review clinical aspects of PD with an emphasis on recent findings. The epidemiology of PD appears to be changing rapidly, with several groups in different parts of the world reporting a marked reduction in the prevalence and incidence of PD, as well as in the severity of disease seen by clinicians. These findings seem most likely to be caused by changes in exposure to unknown environmental factors that have a role in the development of PD. However, genetic factors are also important. Mutations in SQSTM1 occur in 25-50% of familial PD. Genotype-phenotype relationships are present, as PD develops at an earlier age and is more extensive and severe in those with SQSTM1 mutations, and these findings are more pronounced in those with truncating mutations. However, the prevalence of PD in adults with SQSTM1 mutations is uncertain, and it is not known how such mutations might cause PD. Ultimately, if the cause of PD is determined, it seems likely that it will include both genetic and environmental factors. Lastly, clinical trials have shown that potent bisphosphonates are highly effective treatments for active PD, and reduce pain, improve quality of life, normalise bone turnover and heal lytic lesions on radiographs. They can also induce sustained remission that persists for many years.

Clinician approach to diagnosis of stress fractures including bisphosphonate-associated fractures

Stress fractures are repetitive strain injuries that occur in normal bones and in abnormal bones. Stress fractures share many features in common but differences depend on the status of the underlying bone. This review article for clinicians addresses aspects about stress fractures with particular respect to fatigue fractures, Looser zones of osteomalacia, atypical Looser zones, atypical femoral fractures associated with bisphosphonate therapy and stress fractures in Paget's disease of bone.

Malignant degeneration of multilevel monostotic Paget's disease involving the thoracic spine: an unusual presentation

Paget's disease is the second most common metabolic bone disease after osteoporosis and is characterized by abnormal bone turnover and remodeling that can lead to pain, pathological fracture, bony deformity and nerve compression syndromes. The lumbar region is the most commonly affected site within the spine followed by the thoracic and cervical spine. Even though the spine is affected very commonly in Paget's disease, malignant degeneration is exceptionally rare. Multilevel monostotic spine involvement due to Paget's disease is very uncommon. An unusual clinico-radiological manifestation of multilevel thoracic Paget's disease with sarcomatous degeneration presenting as a neurosurgical emergency is reported with a pertinent review of the literature.

Diagnosis and treatment of Paget's disease of bone: a mini-review

Paget's disease of bone (PDB) is a chronic progressive disorder of bone metabolism that may go undetected for many years, and endocrinologists should be alert to its clinical signs and promptly diagnose and treat PDB before it results in irreversible complications, such as deformity, fracture or neurological sequelae. Most commonly, PDB is suspected upon the incidental finding of elevated serum alkaline phosphatase levels or a radiographic abnormality in an otherwise healthy individual above 55 years of age. Some of these individuals may have symptoms such as bone pain or enlargement with increased warmth. In general, a basic laboratory evaluation of bone metabolism, plain radiographies of affected bones and bone scintigraphy are sufficient to corroborate the diagnosis. Antiresorptive therapy with bisphosphonates is the mainstay of treatment of symptomatic PDB, and intravenous zoledronic acid has emerged as an effective and safe treatment option, leading to sustained remission and improved quality of life. It is extremely important, though, to ensure calcium and vitamin D sufficiency before and during treatment in order to prevent hypocalcemia. The benefit of treating all asymptomatic patients is not clear, but treatment is warranted if the pagetic lesion is located in a site where progression to fracture, deformity, or compression would significantly impair the patient quality of life. This mini-review focuses on important aspects of the diagnosis and treatment of PDB.

Common susceptibility alleles and SQSTM1 mutations predict disease extent and severity in a multinational study of patients with Paget's disease

Paget's disease of bone (PDB) has a strong genetic component. Here, we investigated possible associations between genetic variants that predispose to PDB and disease severity. Allelic variants identified as predictors of PDB from genome-wide association studies were analyzed in 1940 PDB patients from the United Kingdom, Italy, Western Australia, and Spain. A cumulative risk allele score was constructed by adding the variants together and relating this to markers of disease severity, alone and in combination with SQSTM1 mutations. In SQSTM1-negative patients, risk allele scores in the highest tertile were associated with a 27% increase in disease extent compared with the lowest tertile (p < 0.00001) with intermediate values in the middle tertile (20% increase; p = 0.0007). The effects were similar for disease severity score, which was 15% (p = 0.01) and 25% (p < 0.00001) higher in the middle and upper tertiles, respectively. Risk allele score remained a significant predictor of extent and severity when SQSTM-positive individuals were included, with an effect size approximately one-third of that observed with SQSTM1 mutations. A genetic risk score was developed by combining information from both markers, which identified subgroups of individuals with low, medium, and high levels of severity with a specificity of 70% and sensitivity of 55%. Risk allele scores and SQSTM1 mutations both predict extent and severity of PDB. It is possible that with further refinement, genetic profiling may be of clinical value in identifying individuals at high risk of severe disease who might benefit from enhanced surveillance and early intervention.

Lipid-enriched diet rescues lethality and slows down progression in a murine model of VCP-associated disease

Valosin-containing protein (VCP)-associated disease caused by mutations in the VCP gene includes combinations of a phenotypically heterogeneous group of disorders such as hereditary inclusion body myopathy, Paget's disease of bone, frontotemporal dementia and amyotrophic lateral sclerosis. Currently, there are no effective treatments for VCP myopathy or dementia. VCP mouse models carrying the common R155H mutation include several of the features typical of the human disease. In our previous investigation, VCP(R155H/R155H) homozygous mice exhibited progressive weakness and accelerated pathology prior to their early demise. Herein, we report that feeding pregnant VCP(R155H/+) heterozygous dams with a lipid-enriched diet (LED) results in the reversal of the lethal phenotype in VCP(R155H/R155H) homozygous offspring. We examined the effects of this diet on homozygous and wild-type mice from birth until 9 months of age. The LED regimen improved survival, motor activity, muscle pathology and the autophagy cascade. A targeted lipidomic analysis of skeletal muscle and liver revealed elevations in tissue levels of non-esterified palmitic acid and ceramide (d18:1/16:0), two lipotoxic substances, in the homozygous mice. The ability to reverse lethality, increase survival, and ameliorate myopathy and lipids deficits in the VCP(R155H/R155H) homozygous animals suggests that lipid supplementation may be a promising therapeutic strategy for patients with VCP-associated neurodegenerative diseases.

Paget's disease of bone: clinical review and update

Paget's disease (PD) is a focal disorder of bone remodelling that occurs commonly in older people. In this article, we review clinical aspects of PD with an emphasis on recent findings. The epidemiology of PD appears to be changing rapidly, with several groups in different parts of the world reporting a marked reduction in the prevalence and incidence of PD, as well as in the severity of disease seen by clinicians. These findings seem most likely to be caused by changes in exposure to unknown environmental factors that have a role in the development of PD. However, genetic factors are also important. Mutations in SQSTM1 occur in 25-50% of familial PD. Genotype-phenotype relationships are present, as PD develops at an earlier age and is more extensive and severe in those with SQSTM1 mutations, and these findings are more pronounced in those with truncating mutations. However, the prevalence of PD in adults with SQSTM1 mutations is uncertain, and it is not known how such mutations might cause PD. Ultimately, if the cause of PD is determined, it seems likely that it will include both genetic and environmental factors. Lastly, clinical trials have shown that potent bisphosphonates are highly effective treatments for active PD, and reduce pain, improve quality of life, normalise bone turnover and heal lytic lesions on radiographs. They can also induce sustained remission that persists for many years.

Ectopic mineralization disorders of the extracellular matrix of connective tissue: molecular genetics and pathomechanisms of aberrant calcification

Ectopic mineralization of connective tissues is a complex process leading to deposition of calcium phosphate complexes in the extracellular matrix, particularly affecting the skin and the arterial blood vessels and common in age-associated disorders. A number of initiating and contributing metabolic and environmental factors are linked to aberrant mineralization in these diseases, making the identification of precise pathomechanistic pathways exceedingly difficult. However, there has been significant recent progress in understanding the ectopic mineralization processes through study of heritable single-gene disorders, which have allowed identification of discrete pathways and contributing factors leading to aberrant connective tissue mineralization. These studies have provided support for the concept of an intricate mineralization/anti-mineralization network present in peripheral connective tissues, providing a perspective to development of pharmacologic approaches to limit the phenotypic consequences of ectopic mineralization. This overview summarizes the current knowledge of ectopic heritable mineralization disorders, with accompanying animal models, focusing on pseudoxanthoma elasticum and generalized arterial calcification of infancy, two autosomal recessive diseases manifesting with extensive connective tissue mineralization in the skin and the cardiovascular system.