Heberden Oration, 1969. Rheumatoid arthritis--nature or nurture?

Familial risk of seropositive rheumatoid arthritis and interaction with smoking: a population-based cohort study

OBJECTIVES

We evaluated the familial risk of seropositive rheumatoid arthritis (RA) and examined interactions between family history and smoking.

METHODS

Using the National Health Insurance and Health Screening Program databases, which include information on familial relationships and lifestyle factors, we identified 5 524 403 individuals with first-degree relatives (FDRs) from 2002-2018. We calculated familial risk using hazard ratios (HRs) with 95% CIs which compare the risk of individuals with and without affected FDRs. Interactions between smoking and family history were assessed on an additive scale using the relative excess risk due to interaction (RERI).

RESULTS

Individuals with affected FDR had 4.52-fold (95% CI 3.98, 5.12) increased risk of disease compared with those with unaffected FDR. Familial risk adjusted for lifestyle factors decreased slightly (HR 4.49), suggesting that a genetic contribution is the predominant driver in the familial aggregation of RA. Smoking was associated with an increased risk of disease that was more pronounced among heavy (HR 1.92 95% CI 1.70, 2.18) compared with moderate (HR 1.15 95% CI 1.04, 1.28) smoking. In the interaction analysis, the risk associated with the combined effect of smoking and family history was higher than the sum of their individual effects, though statistically non-significant (RERI 1.30 95% CI ‒0.92, 3.51). Heavy smokers with a positive family history showed a prominent interaction (RERI 4.13 95% CI ‒0.88, 9.13) which exceeded moderate smokers (RERI 0.61 95% CI ‒1.90, 3.13), suggesting a dose-response interaction pattern.

CONCLUSION

Our findings indicate the possibility of an interaction between RA-associated genes and smoking.

Erosion-free rheumatoid arthritis: clinical and conceptional implications-a BARFOT study

BACKGROUND

Bone erosions may appear early or later during rheumatoid arthritis (RA), causing joint damage and functional impairment. However, in some patients erosions do not occur, even after several years of disease. This study evaluates the prevalence, clinical relevance and possible predictors of erosion-free RA.

METHODS

Six hundred and eight patients from an early RA cohort (BARFOT) having radiographs of hands and feet at inclusion and after 1, 2, 5 and 8 years were studied. Clinical and functional assessments were performed on all these time-points.

RESULTS

In all, 144 patients (24%) did not develop erosions up to 8 years follow-up (Never erosive group), while 464 patients (76%) had erosions on one or more assessments (Ever erosive group). At diagnosis, the patients in the Never erosive group were significantly younger, satisfied fewer ACR criteria, and were less frequently RF- and/or anti-CCP- positive compared with those in the Ever erosive group. The Never erosive patients had consistently more tender joints, lower erythrocyte sedimentation rate (ESR) and, from two years and onwards, fewer swollen joints. Absence of rheumatoid factor (RF) and/or anti-CCP were strong independent predictors for erosion-free disease. The erosion-free patients were less frequently treated with DMARDs and/or prednisolone.

CONCLUSIONS

One-quarter of the patients was erosion-free during eight years in this early RA cohort. Erosion-free patients had a less severe disease course as to disease activity and were more often seronegative compared with those with erosive disease. The results suggest that non-erosive RA represents a milder form of RA.

Metabolic reprogramming in Rheumatoid Arthritis Synovial Fibroblasts: A hybrid modeling approach

Rheumatoid Arthritis (RA) is an autoimmune disease characterized by a highly invasive pannus formation consisting mainly of Synovial Fibroblasts (RASFs). This pannus leads to cartilage, bone, and soft tissue destruction in the affected joint. RASFs' activation is associated with metabolic alterations resulting from dysregulation of extracellular signals' transduction and gene regulation. Deciphering the intricate mechanisms at the origin of this metabolic reprogramming may provide significant insight into RASFs' involvement in RA's pathogenesis and offer new therapeutic strategies. Qualitative and quantitative dynamic modeling can address some of these features, but hybrid models represent a real asset in their ability to span multiple layers of biological machinery. This work presents the first hybrid RASF model: the combination of a cell-specific qualitative regulatory network with a global metabolic network. The automated framework for hybrid modeling exploits the regulatory network's trap-spaces as additional constraints on the metabolic network. Subsequent flux balance analysis allows assessment of RASFs' regulatory outcomes' impact on their metabolic flux distribution. The hybrid RASF model reproduces the experimentally observed metabolic reprogramming induced by signaling and gene regulation in RASFs. Simulations also enable further hypotheses on the potential reverse Warburg effect in RA. RASFs may undergo metabolic reprogramming to turn into "metabolic factories", producing high levels of energy-rich fuels and nutrients for neighboring demanding cells through the crucial role of HIF1.

[Family history of rheumatic diseases in patients with rheumatoid arthritis: a large scale cross-sectional study]

OBJECTIVE

To determine the associations between the family history of rheumatic diseases and clinical features in patients with rheumatoid arthritis (RA).

METHODS

In total, eight hundred and ninety patients with RA were enrolled. The demographic and clinical data were collected, including gender, age, height, body weight, age of disease onset, history of smoking and drinking, family history of rheumatic diseases, clinical and laboratory features, pain and global visual analogue scale (VAS), and multi-dimensional health assessment questionnaire (MDHAQ). Finally, 803 patients were completed the dataset and were included in the study.

RESULTS

In this cohort, the male/female ratio was 1:3.5, and the age of onset was (45.09±14.50) years. A total of 123 (15.32%) patients were accompanied with family history of rheumatic diseases, including RA, spondyloarthritis, Sjögren's syndrome, systemic lupus erythematosus and systemic sclerosis. The percentages of first degree, second degree and both first and second degree relatives were 91 (73.98%), 22 (17.89%), and 10 (8.13%) respectively. The most common disease was RA (70.73%), followed by other rheumatic diseases (21.95%), and RA combined with other rheumatic diseases (7.32%). The clinical and laboratory characteristics were compared between the patients with and without family history. The onset-age of the subjects was significantly different between those with and without family history of rheumatic diseases (39.97 ±13.68 vs. 46.01±14.46; P<0.01), which meant that the onset-age in patients with family history was 6.04 years earlier than that in patients without family history. The patients with family history had higher positive rate of rheumatoid factor (RF) compared with those without family history (78.48% vs. 66.67%, P<0.05). By adjusting with gender, body mass index (BMI), smoking and alcohol drinking, anti-cyclic citrullinated peptide (CCP) antibody and RF level, the age at disease onset in the patients with family history was 4.54 years earlier than that in the patients without family history (β=-4.54; 95%CI:-8.70, -0.38; P<0.05). Further hierarchical regression analysis showed that, the age at onset of the RA patients with family history was 10.02 years earlier than that without family history among the smoking patients (β= -10.02; 95%CI:-17.60, -2.43; P=0.01), while the age at onset of the RA patients with family history was 3.27 years earlier than that without family history among the never smoking patients (β=-3.27; 95%CI:-8.37, 1.82; P=0.21).

CONCLUSION

The family history of rheumatic diseases is a risk factor for early onset of RA, and may interact with smoking.

Quantifying the genetic risk for the development of axial spondyloarthropathy: could this become a diagnostic tool?

PURPOSE OF REVIEW

To assess the utility of recent genetic findings in ankylosing spondylitis (AS) and axial spondyloarthropathy (SpA) in relation to diagnostic testing, prognosis and responses to biologic treatment and the development of new therapies.

RECENT FINDINGS

AS and other forms of SpA are polygenic with more than 100 genes contributing to disease susceptibility. The role of genes in determining the outcome of the disease and response to treatment is less clear. Here, we review some of the progress that has been made over the past decade in understanding the genetic contribution to these diseases and how this may be used to inform the development of new treatments. In those with a high pretest probability of SpA human leukocyte antigen (HLA)-B27 testing can increase the posttest predictive value to almost 100% in some cases. There are currently no reliable genetic predictors of disease severity or response to treatment.

SUMMARY

The utility of HLA-B27 as a diagnostic tool when coupled with careful clinical assessment is well established but other genetic markers probably have relatively little to add. In contrast, novel drug targets are likely to be identified from genetic association studies.

Genetics of rheumatoid arthritis susceptibility, severity, and treatment response

A decade after the first genome-wide association study in rheumatoid arthritis (RA), a plethora of genetic association studies have been published on RA and its clinical or serological subtypes. We review the major milestones in the study of the genetic architecture of RA susceptibility, severity, and response to treatment. We set the scientific context necessary for non-geneticists to understand the potential clinical applications of human genetics and its significance for a stratified approach to the management of RA in the future.

Recent Advances in Defining the Genetic Basis of Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common inflammatory arthritis and exhibits genetic overlap with other autoimmune and inflammatory disorders. Although predominant associations with the HLA-DRB1 locus have been known for decades, recent data have revealed additional insight into the likely causative variants within HLA-DRB1 as well as within other HLA loci that contribute to disease risk. In addition, more than 100 common variants in non-HLA loci have been implicated in disease susceptibility. Genetic factors are involved not only in the development of RA, but also with various disease subphenotypes, including production and circulating levels of autoantibodies and joint destruction. The major current challenge is to integrate these new data into a precise understanding of disease pathogenesis, including the critical cell types and molecular networks involved as well as interactions with environmental factors. We predict that delineating the functional effects of genetic variants is likely to drive new diagnostic and therapeutic approaches to the disease.

Family history of rheumatoid arthritis: an old concept with new developments

Family history of rheumatoid arthritis (RA) is a proxy for an individual's genetic and, in part, environmental risk of developing RA, and is a well-recognized predictor of disease onset. Although family history of RA is an old concept, the degree of familial aggregation of RA, whether it differs by age, sex, or serology, and what value it has for clinical decisions once a diagnosis of RA has been made remain unclear. New data have been emerging in parallel to substantial progress made in genetic association studies. In this Review, we describe the various ways that familial aggregation has been measured, and how the findings from these studies, whether they are based on twins, cohorts of first-degree relatives, or genetic data, correspond to each other and aid understanding of the aetiology of RA. In addition, we review the potential usefulness of family history of RA from a clinical point of view, demonstrating that, in the era of big data and genomics, family history still has a role in directing clinical decision-making and research.

Genetics and epigenetics of rheumatoid arthritis

Investigators have made key advances in rheumatoid arthritis (RA) genetics in the past 10 years. Although genetic studies have had limited influence on clinical practice and drug discovery, they are currently generating testable hypotheses to explain disease pathogenesis. Firstly, we review here the major advances in identifying RA genetic susceptibility markers both within and outside of the MHC. Understanding how genetic variants translate into pathogenic mechanisms and ultimately into phenotypes remains a mystery for most of the polymorphisms that confer susceptibility to RA, but functional data are emerging. Interplay between environmental and genetic factors is poorly understood and in need of further investigation. Secondly, we review current knowledge of the role of epigenetics in RA susceptibility. Differences in the epigenome could represent one of the ways in which environmental exposures translate into phenotypic outcomes. The best understood epigenetic phenomena include post-translational histone modifications and DNA methylation events, both of which have critical roles in gene regulation. Epigenetic studies in RA represent a new area of research with the potential to answer unsolved questions.

Familial rheumatoid arthritis in patients referred to rheumatology clinics of Tabriz, Iran

BACKGROUND

The familial clustering of rheumatoid arthritis (RA) in first and second degree relatives of patients supports the role of genetic factors. The proportion of heredity in its development is roughly 60%; however, most individuals closely related to someone with RA do not get the disease. Considering the lack of sufficient data on the familial aggregation of RA in Iran, we designed this study for clarifying the familial prevalence of RA.

OBJECTIVE

To determine the prevalence of RA among relatives of patients with RA and to evaluate the mean disease onset age in relatives.

METHODS

In a longitudinal study from July 2008 to July 2010, we followed 210 unrelated patients with RA and their first and second degree relatives (FDR+ and SDR+), by interviewing and physical examination of those with symptoms, to ascertain prevalence. Familial RA was defined by presence of at least two siblings fulfilling the 1987 ACR criteria for RA.

RESULTS

We demonstrated that 17.6% of patients have at least one affected relative. The prevalence of RA in the family of studied patients was 0.83% (42 people). Thirty-two in FDR+ and 10 people in SDR+ (2.53% and 0.26% of all family), also 1.12% in female relatives and 0.39% in male relatives had RA. The odds ratio for FDR/SDR was 2.52. The mean age at disease onset in relatives was 42.30 ± 1.51 years in FDR+ and 34.40 ± 2.10 years in the SDR+ group (0.03).

CONCLUSION

The risk of RA is greatest in FDR+ and is likely to be due to a combination of inherited and environmental factors.

Lack of association of TLR4 gene Asp299Gly and Thr399Ile polymorphisms with rheumatoid arthritis in Chinese Han population of Yunnan Province

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of synovium and subsequent joint destruction. Recently, genetic polymorphisms within the toll-like receptor 4 (TLR4) genes have been reported to be associated with RA. To analyze the association between the genetic polymorphisms within TLR4 gene and the susceptibility to RA in Chinese people, two functional variants, Asp299Gly and Thr399Ile, in the TLR4 gene were genotyped using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct sequencing techniques from 213 RA patients and 247 ethnically matched controls. None polymorphisms of Asp299Gly and Thr399Ile were detected in all RA cases and controls, which indicates that there is no relevance between these two SNPs and RA in the Chinese Han population. Further studies with extended single nucleotide polymorphisms (SNP) should be performed.

Recent advances in the genetics of rheumatoid arthritis

PURPOSE OF REVIEW

To review the recently discovered genetic risk loci in rheumatoid arthritis (RA), the pathways they implicate, and the genetic architecture of RA.

RECENT FINDINGS

Since 2008 investigators have identified many common genetic variants that confer disease risk through single nucleotide polymorphism genotyping studies; the list of variants will no doubt continue to expand at a rapid rate as genotyping technologies evolve and case-control sample collections continue to grow. In aggregate, these variants implicate pathways leading to NF-kappaB (nuclear factor kappa-light-chain-enhancer of activated B cells) activation, the interluekin-2 signaling pathway, and T-cell activation.

SUMMARY

Although the effect of any individual variant is modest and even in aggregate considerably less than that of the major histocompatability complex, discovery of recent risk variants suggests immunological processes that are involved in disease pathogenesis.

T Cell Receptor β Gene Polymorphism and Rheumatoid Arthritis

Susceptibility to rheumatoid arthritis is, in part, conferred by genetic factors. Previous studies have suggested that inheritance of a particular allele of a restriction fragment length polymorphism (RFLP) detected in the T cell receptor beta (TCR beta) gene complex is associated with rheumatoid arthritis (RA). We have specifically tested this hypothesis in ethnically and geographically matched populations of RA patients and controls. We were unable to confirm previous observations of a TCR beta association with RA even after stratifying our study and control populations by HLA type.

The molecular genetics of HLA-related disorders

The HLA region on the short arm of chromosome 6 contains a set of highly polymorphic loci responsible for regulating the immune response. Particular haplotypes, defined serologically, have been associated with a risk of developing certain autoimmune diseases such as insulin-dependent (juvenile-onset) diabetes mellitus, multiple sclerosis and rheumatoid arthritis. Recent developments in molecular biology have permitted an improved resolution of the locus and of the sequential arrangement of the susceptibility determinants on these haplotypes. Restriction fragment length polymorphisms have allowed subdivisions of serological haplotypes to be made. These correlate with disease susceptibility in some cases. Amplification of specific HLA class II alleles and nucleic acid sequencing have resulted in the identification of the structural determinants in the HLA that underlie some of these diseases.

Genetic basis of rheumatoid arthritis

Rheumatoid arthritis (RA) is a multifactorial disease due to a combination of genetic and environmental factors. Identification of the genetic factors involved in the pathogenesis of RA should open up avenues for developing radical treatment strategies directed at the cause of the disease. The Association de Recherche sur la Polyarthrite (ARP) supports research in this field, in which our group has been involved since 1993. Thanks to this support, considerable progress has been made. Several combinations of susceptibility alleles of various genes are probably involved in the development of RA. Although HLA-DRB1 is the main RA gene, it accounts for only part of the familial risk for RA. HLA-DRB1 alleles are neither necessary nor sufficient to cause the development of RA in a given individual. Several genome scans conducted in populations from France, Japan, North America and UK have confirmed the role of the HLA region and suggested several other susceptibility loci. Association studies support a role for several genes, including TNFR2, PADI4, SLC22A4, RUNX1, and PTPN22. However, the imperfect matching of cases and controls requires that confirmation of these results be obtained. To confirm that a gene confers susceptibility to RA, the association must be replicated in several independent studies and, more importantly, evidence of genetic linkage must be obtained in family studies. The identification of genetic factors conferring susceptibility to RA will open up new avenues toward radical treatments for RA and may help to optimize the diagnostic, prognostic, and pharmacogenetic management of today's patients with RA.

Association between single-nucleotide polymorphisms in theSEC8L1 gene, which encodes a subunit of the exocyst complex, and rheumatoid arthritis in a Japanese population

OBJECTIVE

To identify rheumatoid arthritis (RA) susceptibility genes in a Japanese population by conducting a large-scale case-control association analysis and linkage disequilibrium (LD) mapping on chromosome 7q31-34, a candidate susceptibility locus identified in a preliminary genome-wide scan in 53 Japanese families, using single-nucleotide polymorphisms (SNPs).

METHODS

We prepared 728 dense, evenly spaced SNPs with a minor allele frequency >0.15 in each gene locus on chromosome 7q31-34. Using these SNPs, a 2-stage case-control analysis was performed on 760 RA patients (157 men and 603 women) and 806 non-RA controls (189 men and 617 women). Haplotypes and LD mapping results were assessed based on SNP genotypes in 380 controls.

RESULTS

Forty-eight SNPs showed allele associations (P < 0.05) in the first set of DNA samples (380 RA cases and 380 non-RA controls; first-stage analysis). For 4 of the SNPs in the SEC8L1 gene, the association was replicated (P < 0.05) in the second, independent set of DNA samples (an additional 380 RA cases and 380 non-RA controls; second-stage analysis). When data from the 2 groups were combined, the most significant allele association was observed with SNP 441, an intronic SNP of the SEC8L1 gene (P = 0.000059). The SEC8L1 SNPs with significant allele associations were all located in a single conserved LD block (block 4). Haplotype analysis revealed the disease-risk (P = 0.0015) and disease-protective (P = 0.0000062) haplotypes. Resequencing of coding exons within block 4 did not identify any nonsynonymous SNPs. Real-time quantitative polymerase chain reaction revealed that SEC8L1 was expressed ubiquitously in human tissues, including fibroblast-like synoviocytes from RA patients.

CONCLUSION

Our locus-wide association and LD analyses identified intronic SNPs and haplotypes in the SEC8L1 gene that are strongly associated with RA. We propose that SEC8L1, which encodes a component of the exocyst complex, is a candidate susceptibility gene for RA in the Japanese population.

Dense genome-wide linkage analysis of rheumatoid arthritis, including covariates

OBJECTIVE

Rheumatoid arthritis (RA) is a heterogeneous disease that exhibits a complex genetic component. Previous RA genome scans confirmed the involvement of the HLA region and generated data on suggestive signals at non-HLA regions, albeit with few overlaps in findings between studies. The present study was undertaken to detect potential RA gene regions and to estimate the number of true RA gene regions, taking into account the heterogeneity of RA, through performance of a dense genome scan.

METHODS

In a study of 88 French Caucasian families (105 RA sibpairs), 1,088 microsatellite markers were genotyped (3.3-cM genome scan), and a multipoint model-free linkage analysis was performed. The statistical assessment of the results relied on 10,000 computer simulations. A covariate-based multipoint model-free linkage analysis was performed on the locations of regions with suggestive evidence for linkage.

RESULTS

Involvement of the HLA region was strongly confirmed (P = 6 x 10(-5)), and 19 non-HLA regions showed suggestive evidence for linkage (P < 0.05); 9 of these overlapped with regions suggested in other published RA genome scans. A routine 12-cM genome scan with the same families would have detected only 7 of the 19 regions, including only 4 of the 9 overlapping regions. From the 10,000 computer simulations, we estimated that 8 +/- 4 regions (mean +/- SD) were true-positives. RA covariate-based analysis provided additional linkage evidence for 3 regions, with age at disease onset, erosions, and HLA-DRB1 shared epitope as covariates.

CONCLUSION

The results of this study provide evidence of 19 non-HLA RA gene regions, with an estimate of 8 +/- 4 as true-positives, and provide additional evidence for 3 regions from covariate-based analysis.

Clustering of disease features within 512 multicase rheumatoid arthritis families

OBJECTIVE

To determine whether specific rheumatoid arthritis (RA) disease features demonstrate the presence of significant familial clustering.

METHODS

We studied 1,097 individuals with RA from 512 multicase families enrolled in the North American Rheumatoid Arthritis Consortium. All patients were interviewed and examined to collect standardized information about demographic and clinical characteristics. Affected individuals also underwent radiography of the hands and wrists and were genotyped for the HLA-DRB1 shared epitope. Familial clustering of disease features was assessed using contingency table analysis and Pearson correlation coefficients. Multivariate logistic and linear regression analyses were used to account for other characteristics that might influence familial clustering, such as disease duration, sex, and age at diagnosis.

RESULTS

Several disease characteristics exhibited significant familial clustering, including seropositivity (multivariate odds ratio [OR] 4.3, P < 0.0001), nodules (OR 2.3, P < 0.0001), and age at RA diagnosis (multivariate regression coefficient [beta] 0.44, P < 0.0001). Other characteristics demonstrated statistically significant but modest degrees of familial clustering (Joint Alignment and Motion score, Health Assessment Questionnaire score, and year of RA diagnosis) or modest but nonsignificant familial clustering (other extraarticular manifestations, other autoimmune diseases).

CONCLUSION

The clustering of certain disease characteristics implicates specific genetic or nongenetic causes. These results highlight the importance of considering disease phenotype in future genetic and epidemiologic studies of RA.

Genetics and clinical practice in rheumatology

The dramatic advances made recently in human genome research are fueling considerable interest in genetic testing. A specific feature of genetic testing is that the results are final and impact not only the patient, but also the entire family. Those elements should be factored into the risk/benefit ratio evaluation. In France, legislation the differentiates diagnostic tests in symptomatic patients from predictive tests in asymptomatic patients with affected family members. Only multidisciplinary groups with both clinical and genetic expertise can order predictive tests. In all cases the physician must sign a statement that informed consent was obtained from the patient prior to testing. The test must be done in an accredited laboratory and the result communicated by the physician to the patient. Patient confidentiality must be respected, particularly regarding family members. In monogenic diseases, the diagnostic weight of genetic testing is often considerable, although the limitations should be borne in mind. In multifactorial diseases, genetic testing seeks to identify risk factors that are usually associated with a low level of risk. The result should be interpreted in the light of the clinical presentation, family history, and genetic background. The predictive value is closely dependent on the clinical presentation but is generally limited, most notably when family members are affected. Great care should be taken to avoid causing undue anxiety among individuals with positive test results. Diseases that illustrate these aspects include Paget's disease of bone, of which inherited variants caused by a mutation in a single gene on chromosome 5 have been identified recently, and rheumatoid arthritis, which is a multifactorial disease.

Experimental neurogenic cystitis

Recent advances in basic and clinical research indicate that interstitial cystitis (IC) is a form of neurogenic inflammation, thereby opening new avenues for research into this painful disease. With this in mind, we have recently developed a rat model of neurogenic inflammation of the bladder produced by a central nervous system viral disease. As in IC, the inflammation in this model develops without direct injury or trauma to the bladder, is non-infectious, and is limited to the bladder. Our most recent studies aimed at further testing the similarity of this animal model to IC by assessing the urine content in histamine with the occurrence of mast cell degranulation in the bladder wall. We further verified for a sex difference in the occurrence of the disease. Our results showed increased levels of urine histamine and mast cell activation during the early stages of the disease. We additionally observed that females had a greater degree of plasma extravasation, while males had a greater cellular infiltration together with worse behavioral signs. Gonadectomy prevented the bladder inflammation altogether in both males and females. These findings further validate our model of neurogenic cystitis to study the neurogenic component of IC.

Association between tumor necrosis factor receptor II and familial, but not sporadic, rheumatoid arthritis: evidence for genetic heterogeneity

OBJECTIVE

Tumor necrosis factor alpha (TNFalpha) binds the receptors TNFRI and TNFRII. Results of genome scans have suggested that TNFR2 is a candidate rheumatoid arthritis (RA) locus. A case-control study in a UK Caucasian population has shown an association between a TNFR2 genotype (196R/R in exon 6) and familial, but not sporadic, RA. The present study was undertaken to test this association in the French Caucasian population.

METHODS

To test for an association in sporadic RA, 100 families were genotyped for the 196M/R polymorphism and analyzed using the transmission disequilibrium test and haplotype relative risk. To test for an association in familial RA, RA index cases from 100 affected sibpair (ASP) families were genotyped for 196M/R. Linkage analysis was performed with 3 TNFR2 microsatellite markers.

RESULTS

The TNFR2 196R/R genotype was not associated with sporadic RA (odds ratio [OR] 0.59, P = 0.72), but was associated with familial RA (OR 4.0, P = 0.026). The association was most marked in the context of TNFR2 "twin-like" RA sibs (affected sibs sharing both TNFR2 haplotypes) (OR 9.2, P = 0.0017). Linkage analysis results were consistent with the association; most of the TNFR2 linkage evidence was found in the subgroup of families with 196R/R ASP index cases.

CONCLUSION

This study is the first to replicate evidence of the involvement of TNFR2 in RA genetic heterogeneity. Our data refine the initial hypothesis, to suggest that a TNFR2 recessive factor, in linkage disequilibrium with the 196R allele, plays a major role in a subset of families with multiple cases of RA.

Research in complex diseases

Many diseases that have a substantial effect on health have a complex pathogenesis. Examples are atherosclerosis, diabetes mellitus, and rheumatoid arthritis. Here, we discuss a hierarchy of goals of research in complex diseases, and introduce a stepwise approach for the development of disease models, paying specific attention to the position of genetic factors and stochastic variables in these models.

Relative importance of genetic effects in rheumatoid arthritis: historical cohort study of Danish nationwide twin population

OBJECTIVE

To determine the relative importance of environmental and genetic effects in the development of rheumatoid arthritis.

DESIGN

Historical cohort study with record linkage between a twin registry and the Danish discharge registry as well as the Danish national registry of deaths used to estimate completeness.

SETTING

Two population based nationwide twin birth cohorts.

PARTICIPANTS

37 338 twins were sent a questionnaire about rheumatic diseases. Self reported rheumatoid arthritis was verified by clinical examination and from medical records.

MAIN OUTCOME MEASURES

The probandwise concordance rate of rheumatoid arthritis in monozygotic and dizygotic twins.

RESULTS

The response rate was 84.7%. Rheumatoid arthritis was verified in 13 monozygotic and 36 dizygotic twins. There were no concordant monozygotic twin pairs and two concordant dizygotic twin pairs. Based on capture-recapture methods the probability of ascertainment was 78.3%. The probandwise concordance rate was 0 (95% confidence interval 0 to 24.7) in monozygotic twins and 8.8 (1.9 to 23.7) in dizygotic twins.

CONCLUSION

Genes are of minor importance in the development of rheumatoid arthritis.

Epidemiology and genetics of rheumatoid arthritis

The prevalence of rheumatoid arthritis (RA) is relatively constant in many populations, at 0.5-1.0%. However, a high prevalence of RA has been reported in the Pima Indians (5.3%) and in the Chippewa Indians (6.8%). In contrast, low occurrences have been reported in populations from China and Japan. These data support a genetic role in disease risk. Studies have so far shown that the familial recurrence risk in RA is small compared with other autoimmune diseases. The main genetic risk factor of RA is the HLA DRB1 alleles, and this has consistently been shown in many populations throughout the world. The strongest susceptibility factor so far has been the HLA DRB1*0404 allele. Tumour necrosis factor alleles have also been linked with RA. However, it is estimated that these genes can explain only 50% of the genetic effect. A number of other non-MHC genes have thus been investigated and linked with RA (e.g. corticotrophin releasing hormone, oestrogen synthase, IFN-gamma and other cytokines). Environmental factors have also been studied in relation to RA. Female sex hormones may play a protective role in RA; for example, the use of the oral contraceptive pill and pregnancy are both associated with a decreased risk. However, the postpartum period has been highlighted as a risk period for the development of RA. Furthermore, breastfeeding after a first pregnancy poses the greatest risk. Exposure to infection may act as a trigger for RA, and a number of agents have been implicated (e.g. Epstein-Barr virus, parvovirus and some bacteria such as Proteus and Mycoplasma). However, the epidemiological data so far are inconclusive. There has recently been renewed interest in the link between cigarette smoking and RA, and the data presented so far are consistent with and suggestive of an increased risk.

The inheritance of rheumatoid arthritis in Iceland

OBJECTIVE

Rheumatoid arthritis (RA) is the most common form of inflammatory arthritis. Although there is a large body of evidence suggesting that RA is immune mediated, the etiology remains unresolved. Twin studies have shown disease concordance rates of approximately 15% in monozygotic twins and 4% in dizygotic twins, while the estimated risk ratio for siblings of RA patients ranges from 5 to 8. Our goal was to use genealogic data from Iceland to further investigate the genetic component of RA.

METHODS

Data were obtained from a population-based, computerized genealogy database that was developed to examine multigenerational relationships among individuals in the relatively homogeneous population of Iceland. Using an algorithm, the minimum founder test, we calculated the least number of founders required to account for a list of RA patients, and compared it with 1,000 sets of same-sized matched control groups. In addition, we estimated the kinship coefficient and risk ratios for relatives of the RA patients.

RESULTS

Several familial clustering tests demonstrated that the RA patients were more related to each other than were the average control set of Icelanders. A significantly fewer number of founders was necessary to account for our patient list than for the random sets of matched controls (P < 0.001), and the average pairwise identity-by-descent sharing was greater among the patients than among the control sets (P < 0.001). In addition, there was an increased risk of RA in first- and second-degree relatives of the patients; e.g., for siblings, the risk ratio was 4.38 (95% confidence interval 3.26-5.67), and for uncles/aunts, the risk ratio was 1.95 (95% confidence interval 1.52-2.43).

CONCLUSION

The familial component of RA is shown to extend beyond the nuclear family, thus providing stronger evidence for a significant genetic component to RA.

Anti-TNF alpha therapy of rheumatoid arthritis: what have we learned?

Rheumatoid arthritis (RA), a systemic disease, is characterized by a chronic inflammatory reaction in the synovium of joints and is associated with degeneration of cartilage and erosion of juxta-articular bone. Many pro-inflammatory cytokines including TNF alpha, chemokines, and growth factors are expressed in diseased joints. The rationale that TNF alpha played a central role in regulating these molecules, and their pathophysiological potential, was initially provided by the demonstration that anti-TNF alpha antibodies added to in vitro cultures of a representative population of cells derived from diseased joints inhibited the spontaneous production of IL-1 and other pro-inflammatory cytokines. Systemic administration of anti-TNF alpha antibody or sTNFR fusion protein to mouse models of RA was shown to be anti-inflammatory and joint protective. Clinical investigations in which the activity of TNF alpha in RA patients was blocked with intravenously administered infliximab, a chimeric anti-TNF alpha monoclonal antibody (mAB), has provided evidence that TNF regulates IL-6, IL-8, MCP-1, and VEGF production, recruitment of immune and inflammatory cells into joints, angiogenesis, and reduction of blood levels of matrix metalloproteinases-1 and -3. Randomized, placebo-controlled, multi-center clinical trials of human TNF alpha inhibitors have demonstrated their consistent and remarkable efficacy in controlling signs and symptoms, with a favorable safety profile, in approximately two thirds of patients for up to 2 years, and their ability to retard joint damage. Infliximab (a mAB), and etanercept (a sTNF-R-Fc fusion protein) have been approved by regulatory authorities in the United States and Europe for treating RA, and they represent a significant new addition to available therapeutic options.

Heavy cigarette smoking is strongly associated with rheumatoid arthritis (RA), particularly in patients without a family history of RA

OBJECTIVES

To investigate the potential relation between cumulative exposure to cigarette smoking in patients with or without rheumatoid arthritis (RA) and a positive family history of the disease.

METHODS

239 outpatient based patients with RA were compared with 239 controls matched for age, sex, and social class. A detailed smoking history was recorded and expressed as pack years smoked. Conditional logistic regression was used to calculate the association between RA and pack years smoked. The patients with RA were also interviewed about a family history of disease and recorded as positive if a first or second degree relative had RA. The smoking history at the time of the study of the patients with RA with or without a family history of the disease was compared directly with that of their respective controls. Patients with RA with or without a family history of the disease were also compared retrospectively for current smoking at the time of disease onset.

RESULTS

An increasing association between increased pack years smoked and RA was found. There was a striking association between heavy cigarette smoking and RA. A history for 41-50 pack years smoked was associated with RA (odds ratio (OR) 13.54, 95% confidence interval (95% CI) 2.89 to 63.38; p<0.001). The association between ever having smoked and RA was modest (OR 1.81, CI 1.22 to 2.19; p=0.002). Furthermore, cigarette smoking in the patients with RA without a positive family history of RA was more prevalent than in the patients with a positive family history of RA for ever having smoked (72% v 54%; p=0.006), the number of pack years smoked (median 25.0 v 4.0; p<0.001), and for smoking at the time of disease onset (58% v 39%; p=0.003).

CONCLUSIONS

Heavy cigarette smoking, but not smoking itself, is strongly associated with RA requiring hospital follow up and is markedly more prevalent in patients with RA without a family history of RA.

Tumor necrosis factor markers show sex-influenced association with rheumatoid arthritis

OBJECTIVE

The observation that not all shared-epitope genotypes confer the same risk suggests that a second HLA-region locus may confer risk. Tumor necrosis factor alpha (TNFgamma) is a possible candidate. We examined TNFalpha for sex influences on HLA-associated risk for rheumatoid arthritis (RA).

METHODS

DRB1 and TNF microsatellite typing of 297 Caucasian RA patients (132 men, 165 women) and 267 Caucasian controls was performed.

RESULTS

The TNFab microsatellite haplotype distribution differed among the male RA, female RA, and control groups (P < 0.01); the difference was largely an excess of TNFa2b1 haplotypes in the male RA group. However, this did not simply reflect an excess of shared-epitope haplotypes bearing TNFa2b1. In RA, not all shared-epitope-bearing haplotypes had the same TNFab. The *0401-bearing haplotypes commonly had TNFa6b5, TNFa2b1, TNFa10b4, and TNFa11b4, while the *0404-bearing haplotypes had TNFa11b4. In the female RA group, TNFa2b1 was most often on *0401-bearing haplotypes. In the male RA group, there was a surprise: TNFa2b1 was often on HLA haplotypes without shared-epitope DRB1 alleles. To estimate the relative strength of associated HLA markers, we performed logistic regression analyses stratified by sex and controlling for a potential confounder, age at disease onset. Among women, TNFa2b3 favored RA (odds ratio 1.932, P < 0.05) while TNFa6b5 was protective (odds ratio 0.522, P < 0.05). Among males, TNFa2b1 and TNFa11b4 conferred elevated odds ratios (2.58 and 1.681, respectively, P < 0.05). However, the odds ratios for TNFa2b1 in men and TNFa2b3 in women were generally well below those for RA-associated DRB1 markers (for example, DRB1*0401 3.553 in male RA patients and 6.991 in female RA patients).

CONCLUSION

Certain TNFab-bearing HLA haplotypes modify RA risk in a manner influenced by sex but independent of DRB1, particularly TNFa2b1 in men.

Update on the genetics of the idiopathic inflammatory myopathies

A number of lines of investigation suggest that, as is likely the case for other autoimmune diseases, the idiopathic inflammatory myopathies (IIM) develop as a result of specific environmental exposures in genetically susceptible individuals. Current data imply that multiple genes are involved in the etiology of these complex disorders. Targeted gene studies and whole genome approaches have begun to identify several genetic risk factors for autoimmune diseases, but the rarity and heterogeneity of the IIM have limited our knowledge of their associated genes. Current findings suggest that human leukocyte antigen (HLA) genes on chromosome 6, particularly HLA DRB1*0301 and the linked allele DQA1*0501, have the strongest associations with all clinical forms of IIM in white patients. Different HLA alleles, however, may confer risk or protection for myositis in distinct ethnic, serologic, and environmental exposure groups. Non-HLA genetic risk factors, which have been documented for other autoimmune diseases, are now being identified for the IIM. These include polymorphic genes encoding immunoglobulin heavy chains (defined by serologic markers known as Gm allotypes), cytokines and their receptors, and certain proteins that accumulate in the myocyte vacuoles of inclusion body myositis patients. Selected allelic polymorphisms of interleukin-1 receptor antagonist variable number tandem repeats and genes for tumor necrosis factor alpha and interleukin-1 alpha also have recently been associated with IIM. The pathogenic bases for the differences among the many clinically, pathologically and immunologically defined syndromes known as the IIM will be elucidated through a better understanding of the multiple genes that define risks for their development, as well as through investigations of gene-gene and gene-environment interactions.

Hormonal and immunologic risk factors for the development of rheumatoid arthritis: an integrative physiopathogenetic perspective

Evidence indicates that women who are susceptible to premenopausal onset of RA and men each have identifiable risk factors or risk markers long before onset of the clinical disease. Accordingly, further definition of such predictive factors promises to identify persons who are susceptible to developing RA during preclinical phases. Like coronary artery disease, once risks for developing RA can be reliably quantitated, research in primary prevention should become a realistic objective. Disease prevention objectives are central to the public health strategy of the National Arthritis Action Plan and the US Public Health Service "Healthy People 2000" plan (2010 plan also proposed). The decade of arthritis and musculoskeletal diseases (2000-2010) offers an incentive to nurture a new paradigm of RA prevention. Further research in neuroendocrine, immunologic, and microvascular risk factors for the development of RA promises to unravel its complex physiopathogenetic mechanisms and permit identification of persons who are at high risk for developing this disease. Successful research in identifying reliable risk factors (or markers) can be expected to lead to prevention strategies. Effective programs in identifying persons susceptible to RA could lead to earlier control measures and significantly reduce the enormous burden of this common disease, which affects all segments of the population.

Familial autoimmunity and the idiopathic inflammatory myopathies

Many lines of evidence suggest that autoimmune diseases result from chronic immune activation following environmental exposures in genetically susceptible individuals. A genetic basis for autoimmunity is supported by twin and family studies, candidate gene investigations, animal models, and whole genome microsatellite scans. These findings predict, and clinical observations support, familial clustering of a number of individual autoimmune diseases, notably lupus, multiple sclerosis, type-1 diabetes mellitus, rheumatoid arthritis, and recently the idiopathic inflammatory myopathies. Yet, not only is the same autoimmune disease increased in prevalence in pedigrees of persons affected with a given disorder, but other autoimmune diseases are as well. We review these data and propose a hypothesis consistent with these findings. This model posits that a rheumatic disease, as currently classified, is actually composed of a number of elemental disorders. Each of these is defined by the minimal necessary and sufficient environmental exposures and genes that result in a pathology leading to a given sign-symptom complex.

Analysis of TAP and HLA-DM polymorphism in thai rheumatoid arthritis

Rheumatoid arthritis is an autoimmune disease with a strong association with DR4 in many populations. In the Thai population, rheumatoid arthritis is associated with DRB1*0405. To evaluate the role of polymorphism in TAP and HLA-DM genes, which are important in antigen processing and presentation in predisposition to rheumatoid arthritis, 82 Thai patients with rheumatoid arthritis and 100 unrelated normal controls were studied. TAP and HLA-DM typing was performed by ARMS-PCR and PCR-SSO method, respectively. There was no difference in the distribution of TAP1, TAP2, DMA, and DMB genes between the patients and controls. This study suggested that TAP and HLA-DM genes do not confer susceptibility to rheumatoid arthritis.

Immunogenetic differences between patients with familial and non-familial rheumatoid arthritis

OBJECTIVE

To search for possible immunogenetic differencies between the patients with familial and non-familial rheumatoid arthritis (RA).

METHODS

The study compared 129 familial RA patients with 217 non-familial patients for the frequencies of HLA-DR antigens including DR4 subtypes, DR4-DQB1*0301 and DR4-DQB1*0302 haplotypes and HLA-B27 antigen as well as the age of disease onset and existence of rheumatoid factor or joint erosions.

RESULTS

Two major differences between familial and non-familial groups were found: firstly, familial RA patients had increased frequency of HLA-DR4 as compared with the non-familial RA group (68.2 v. 54.8%; p = 0.019). Secondly, the mean age at onset of RA was significantly lower in the familial than in the sporadic RA patients (42.0 v. 46.5 years; p = 0.0020) and the difference still remained when the DR4 positive and negative subgroups were compared separately.

CONCLUSION

These results confirm the more prominent association with HLA-DR4 in familial than in the non-familial cases and suggest that accumulation of HLA risk genes may, at least partly, explain the familial occurrence of the disease. Other susceptibility genes may also be concentrated in multiplex case families as suggested by an earlier age at the onset of RA in both HLA-DR4 positive and negative familial patients.

Genealogy construction in a historically isolated population: application to genetic studies of rheumatoid arthritis in the Pima Indian

PURPOSE

Due to the characteristics of complex traits, many traits may not be amenable to traditional epidemiologic methods. We illustrate an approach that defines an isolated population as the "unit" for carrying out studies of complex disease. We provide an example using the Pima Indians, a relatively isolated population, in which the incidence and prevalence of Type 2 diabetes, gallbladder disease, and rheumatoid arthritis (RA) are significantly increased compared with the general U.S. population. A previous study of RA in the Pima utilizing traditional methods failed to detect a genetic effect on the occurrence of the disease.

METHODS

Our approach involved constructing a genealogy for this population and using a genealogic index to investigate familial aggregation. We developed an algorithm to identify biological relationships among 88 RA cases versus 4,000 subsamples of age-matched individuals from the same population. Kinship coefficients were calculated for all possible pairs of RA cases, and similarly for the subsamples.

RESULTS

The sum of the kinship coefficient among all combination of RA pairs, 5.92, was significantly higher than the average of the 4,000 subsamples, 1.99 (p < 0.001), and was elevated over that of the subsamples to the level of second cousin, supporting a genetic effect in the familial aggregation. The mean inbreeding coefficient for the Pima was 0.00009, similar to that reported for other populations; none of the RA cases were inbred.

CONCLUSIONS

The Pima genealogy can be anticipated to provide valuable information for the genetic study of diseases other than RA. Defining an isolated population as the "unit" in which to assess familial aggregation may be advantageous, especially if there are a limited number of cases in the study population.

New susceptibility locus for rheumatoid arthritis suggested by a genome-wide linkage study

Rheumatoid arthritis (RA), the most common autoimmune disease, is associated in families with other autoimmune diseases, including insulin-dependent diabetes mellitus (IDDM). Its genetic component has been suggested by familial aggregation (lambdas = 5), twin studies, and segregation analysis. HLA, which is the only susceptibility locus known, has been estimated to account for one-third of this component. The aim of this paper was to identify new RA loci. A genome scan was performed with 114 European Caucasian RA sib pairs from 97 nuclear families. Linkage was significant only for HLA (P < 2.5.10(-5)) and nominal for 19 markers in 14 other regions (P < 0.05). Four of the loci implicated in IDDM potentially overlap with these regions: the putative IDDM6, IDDM9, IDDM13, and DXS998 loci. The first two of these candidate regions, defined in the RA genome scan by the markers D18S68-D18S61-D18S469 (18q22-23) and D3S1267 (3q13), respectively, were studied in 194 additional RA sib pairs from 164 nuclear families. Support for linkage to chromosome 3 only was extended significantly (P = 0.002). The analysis of all 261 families provided a linkage evidence of P = 0. 001 and suggested an interaction between this putative RA locus and HLA. This locus could account for 16% of the genetic component of RA. Candidate genes include those coding for CD80 and CD86, molecules involved in antigen-specific T cell recognition. In conclusion, this first genome scan in RA Caucasian families revealed 14 candidate regions, one of which was supported further by the study of a second set of families.

Severe rheumatoid arthritis prohibits the pregnancy-induced decrease in alpha3-fucosylation of alpha1-acid glycoprotein

Patients suffering from rheumatoid arthritis (RA) may experience a temporary reduction of disease symptoms during pregnancy. As indicated by the occurrence of RA-disease symptoms during pregnancy, three categories of patients were defined, namely, remission, relapse and unchanged. In all three categories changes in the plasma level and glycosylation of alpha1-acid glycoprotein (AGP) were determined longitudinally in comparison to those occurring in pregnancy of healthy women. In healthy pregnancy, we observed: (i) a peak in the plasma concentration at week 18 and a minimum at week 30; (ii) a continuous increase in the degree of branching of the glycans during the entire pregnancy period, and (iii) a decrease in the degree of alpha3-fucosylation of AGP-glycans with a minimum occurring at week 25. Comparable pregnancy-induced changes in glycosylation were found for two other acute-phase proteins alpha1-protease inhibitor (PI) and alpha1-antichymotrypsin (ACT). Increased oestrogen levels, known to occur during pregnancy, may be one of the factors that induce these changes, because the increased branching and decreased alpha3-fucosylation is in agreement with our earlier findings regarding an involvement of this hormone in the regulation of acute phase protein glycosylation in oestrogen-treated males as well as females. In all three clinical categories in RA, pregnancy also induced a continuous increase in the degree of branching of the glycans of AGP. However, similar changes in concentration and fucosylation were only found during remission of the disease symptoms. In the relapse and unchanged categories in RA, the degree of fucosylation and the plasma concentration of AGP remained constant throughout pregnancy. This indicates a relationship between changes in alpha3-fucosylation of AGP and RA disease activity.

A methodological appraisal of the impact of different classification procedures used in three different phases of the australian rheumatoid arthritis twin survey

AIMS

To compare methodological aspects of the impact of different classification procedures used in three phases of a twin study examining genetic factors in the aetiopathogenesis of rheumatoid arthritis (RA).

METHODS

We have previously reported the results of a study of the aetiopathogenesis of RA based on the Australian Twin Registry (ATR). In the original 258 pairs self-reporting a diagnosis of RA in twin, co-twin or both, a very high false positive self-reporting rate for RA was noted (Phase 1). Subsequent diagnostic information obtained by a disease-specific questionnaire, followed by telephone interviews with subjects and review of information obtained by mail and telephone interview from the patient's general practitioner or musculoskeletal specialist, identified 23 'true' RA pairs (Phase 2). Pairwise concordance percentages for RA based on those 20 discordant and 3 concordant pairs were as follows: monozygotic (MZ) 21% (95% confidence interval (CI)=6-44%), dizygotic (DZ) 0% (95% CI=0-25%) (probandwise concordance MZ 35% (8.9-67.3), DZ 0% (0-50.3)). Given the potential effects of misclassification on data interpretation, we have further pursued the accuracy of diagnosis by a systematic clinical, serological and radiographical evaluation of the 23 RA pairs (Phase 3).

RESULTS

In only one instance did more intense diagnostic investigation of the 23 pairs result in recategorization. The probandwise concordance percentages were recalculated: MZ=37.5%, DZ=0%.

CONCLUSIONS

Our original contention that genetic factors play some part in the aetiopathogenesis of RA, but do not account entirely for its determination, has been substantiated at a higher level of confidence and at almost identical levels of concordance.

The HLA-DQ7 and -DQ8 associations in DR4-positive rheumatoid arthritis patients. A combined analysis of data available in the literature

Several different lines of evidence have demonstrated that inherited susceptibility to rheumatoid arthritis (RA) is associated with the DRB1 genes encoding the HLA-DR4 and HLA-DR1 molecules. A contrasting hypothesis has recently been proposed, suggesting that, in general, the DRB1 locus is associated with protection to RA and that the RA-associated DRB1 alleles are not responsible for the primary disease association but merely permissive for the susceptibility conferred by the HLA-DQ alleles with which they are in linkage disequilibrium. We have performed a critical review of the literature on the HLA association in RA with special emphasis on studies in which both an HLA-DR and -DQ association has been investigated. Our analyses provide strong evidence against the hypothesis that HLA-DQ molecules play a major role in the general susceptibility to RA. Thus, the strongest association in rheumatoid arthritis is with DRB1 genes rather than DQB1 genes.

HLA-DRB1 in eight Finnish monozygotic twin pairs concordant for rheumatoid arthritis

This study presents the results of HLA-DRB1 typing of the eight monozygotic twin pairs with both members affected by rheumatoid arthritis (RA), sampled in the nationwide Finnish twin cohort. The shared epitope, associated with RA in case-control studies, was present in all eight twin pairs, being significantly more frequent than among RA patients in a recent Dutch case-control study. Furthermore, 4 out of 8 twin pairs were homozygous for the shared epitope, while in 73 Dutch healthy controls encoding the shared epitope only 13 (18%) were homozygous: this suggests a gene dose effect in RA susceptibility. Combining these results with data from other sources may help to clarify the contribution of HLA alleles in the genetic predisposition to RA.