Occurrence of rheumatoid arthritis is not increased in the first degree relatives of a population based inception cohort of inflammatory polyarthritis

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.

Assessing prognosis and prediction of treatment response in early rheumatoid arthritis: systematic reviews

BACKGROUND

Rheumatoid arthritis (RA) is a chronic, debilitating disease associated with reduced quality of life and substantial costs. It is unclear which tests and assessment tools allow the best assessment of prognosis in people with early RA and whether or not variables predict the response of patients to different drug treatments.

OBJECTIVE

To systematically review evidence on the use of selected tests and assessment tools in patients with early RA (1) in the evaluation of a prognosis (review 1) and (2) as predictive markers of treatment response (review 2).

DATA SOURCES

Electronic databases (e.g. MEDLINE, EMBASE, The Cochrane Library, Web of Science Conference Proceedings; searched to September 2016), registers, key websites, hand-searching of reference lists of included studies and key systematic reviews and contact with experts.

STUDY SELECTION

Review 1 - primary studies on the development, external validation and impact of clinical prediction models for selected outcomes in adult early RA patients. Review 2 - primary studies on the interaction between selected baseline covariates and treatment (conventional and biological disease-modifying antirheumatic drugs) on salient outcomes in adult early RA patients.

RESULTS

Review 1 - 22 model development studies and one combined model development/external validation study reporting 39 clinical prediction models were included. Five external validation studies evaluating eight clinical prediction models for radiographic joint damage were also included. c-statistics from internal validation ranged from 0.63 to 0.87 for radiographic progression (different definitions, six studies) and 0.78 to 0.82 for the Health Assessment Questionnaire (HAQ). Predictive performance in external validations varied considerably. Three models [(1) Active controlled Study of Patients receiving Infliximab for the treatment of Rheumatoid arthritis of Early onset (ASPIRE) C-reactive protein (ASPIRE CRP), (2) ASPIRE erythrocyte sedimentation rate (ASPIRE ESR) and (3) Behandelings Strategie (BeSt)] were externally validated using the same outcome definition in more than one population. Results of the random-effects meta-analysis suggested substantial uncertainty in the expected predictive performance of models in a new sample of patients. Review 2 - 12 studies were identified. Covariates examined included anti-citrullinated protein/peptide anti-body (ACPA) status, smoking status, erosions, rheumatoid factor status, C-reactive protein level, erythrocyte sedimentation rate, swollen joint count (SJC), body mass index and vascularity of synovium on power Doppler ultrasound (PDUS). Outcomes examined included erosions/radiographic progression, disease activity, physical function and Disease Activity Score-28 remission. There was statistical evidence to suggest that ACPA status, SJC and PDUS status at baseline may be treatment effect modifiers, but not necessarily that they are prognostic of response for all treatments. Most of the results were subject to considerable uncertainty and were not statistically significant.

LIMITATIONS

The meta-analysis in review 1 was limited by the availability of only a small number of external validation studies. Studies rarely investigated the interaction between predictors and treatment.

SUGGESTED RESEARCH PRIORITIES

Collaborative research (including the use of individual participant data) is needed to further develop and externally validate the clinical prediction models. The clinical prediction models should be validated with respect to individual treatments. Future assessments of treatment by covariate interactions should follow good statistical practice.

CONCLUSIONS

Review 1 - uncertainty remains over the optimal prediction model(s) for use in clinical practice. Review 2 - in general, there was insufficient evidence that the effect of treatment depended on baseline characteristics.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016042402.

FUNDING

The National Institute for Health Research Health Technology Assessment programme.

Familial aggregation of rheumatoid arthritis and co-aggregation of autoimmune diseases in affected families: a nationwide population-based study

Objective

The aim was to estimate familial relative risk (RR) for RA and other autoimmune diseases and the genetic contribution to RA phenotypic variance (heritability).

Methods

This study used the Taiwan National Health Insurance Research Database to identify all National Health Insurance registered beneficiaries (n = 23 658 577) in 2010; among them, 37 482 individuals had RA. We estimated familial RRs and 95% CIs of RA and other autoimmune diseases using marginal Cox proportional models and heritability of RA using a threshold liability model.

Results

The RR (95% CI) for RA was 328.27 (135.95, 795.63) for twins of RA patients; 11.97 (8.68, 16.52) for siblings; 4.86 (4.16, 5.67) for parents; 4.65 (3.92, 5.50) for offspring; and 2.32 (1.83, 2.95) for spouses. Using a threshold liability model, we estimated that familial transmission was 59.4% (95% CI: 50.3, 69.5%) and that heritability was 43.5% (33.9, 54.1%). The RR (95% CI) in individuals with a first-degree relative with RA was 2.91 (2.49, 3.42) for SLE; 2.92 (1.62, 5.25) for SSc; 3.13 (2.50, 3.93) for primary SS; 0.95 (0.36, 2.51) for idiopathic inflammatory myositis; 1.96 (1.54, 2.48) for type 1 diabetes mellitus; 3.32 (1.82, 5.95) for multiple sclerosis; 1.31 (1.31, 2.43) for IBD; 2.76 (2.46, 3.10) for AS; and 1.65 (1.54, 1.77) for psoriasis.

Conclusion

The risks of RA and other autoimmune diseases increased in individuals with an RA family history. Approximately two-thirds of RA phenotypic variation is explained by familial factors.

The recurrence risk of genetic complex diseases

Complex inherited diseases affected by an interaction between collective effects of the genotype at one or multiple loci either to increase or to lower susceptibility to disease, combined with a variety of environmental exposures that may trigger, accelerate, exacerbate, or protect against the disease process. The new aspects of genetic techniques have been opened for diagnosis and analysis of inherited disorders. While appropriate Mendelian laws is applied to estimate the recurrence risk of single gene diseases, using empirical recurrence risks are the most important and available method to evaluate pedigree of complex (multifactorial), chromosomal, and unknown etiology disorders. Although, generally, empirical recurrent risks are not accurate, either because of the difference of gene frequencies and environmental factors among populations or heterogeneity of disease; using results of plenty family population studies, computerized estimating programs, genotyping technologies, and Genome-wide association studies (GWASs) of single nucleotide polymorphisms (SNPs), can make it possible nowadays to estimate these risks. The specific family situation and importance recurrence risks of some common complex genetic diseases will be presented in this review and some important multifactorial disorders’ recurrence risks will be summarized to help genetic counselors for supporting families and representing better view of genetic disorders.

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.

Prediction of future rheumatoid arthritis

Rheumatoid arthritis (RA) results from an interaction between genetic susceptibility and environmental factors. Several of these factors are known, such as family history of RA, high birth weight, smoking, silica exposure, alcohol nonuse, obesity, diabetes mellitus, rheumatoid factor, anti-citrullinated protein antibody, and genetic variants such as the shared epitope and protein tyrosine phosphatase nonreceptor type 22. The impact of these factors can be modeled in the 2 main groups at risk of RA: family members of patients with RA and seropositive persons with or without arthralgia. Current models have the potential to select individuals for preventive strategies.

The immunopathology of ANCA-associated vasculitis

The small-vessel vasculitides are a group of disorders characterised by variable patterns of small blood vessel inflammation producing a markedly heterogeneous clinical phenotype. While any vessel in any organ may be involved, distinct but often overlapping sets of clinical features have allowed the description of three subtypes associated with the presence of circulating anti-neutrophil cytoplasmic antibodies (ANCA), namely granulomatosis with polyangiitis (GPA, formerly known as Wegener’s Granulomatosis), microscopic polyangiitis (MPA) and eosinophilic granulomatosis with polyangiitis (eGPA, formerly known as Churg-Strauss syndrome). Together, these conditions are called the ANCA-associated vasculitidies (AAV). Both formal nomenclature and classification criteria for the syndromes have changed repeatedly since their description over 100 years ago and may conceivably do so again following recent reports showing distinct genetic associations of patients with detectable ANCA of distinct specificities. ANCA are not only useful in classifying the syndromes but substantial evidence implicates them in driving disease pathogenesis although the mechanism by which they develop and tolerance is broken remains controversial. Advances in our understanding of the pathogenesis of the syndromes have been accompanied by some progress in treatment, although much remains to be done to improve the chronic morbidity associated with the immunosuppression required for disease control.

Familial risks and heritability of rheumatoid arthritis: role of rheumatoid factor/anti-citrullinated protein antibody status, number and type of affected relatives, sex, and age

OBJECTIVE

To estimate familial aggregation of rheumatoid arthritis (RA) in 3 large population-representative samples and to test if familial aggregation is affected by rheumatoid factor (RF)/anti-citrullinated protein antibody (ACPA) status, type of relative, sex, and age at onset of RA.

METHODS

A register-based nested case-control study was performed in the Swedish total population. Data on patients with RA were ascertained through the nationwide Swedish Patient Register (n = 88,639), the clinical Swedish Rheumatology Quality Register (n = 11,519), and the Epidemiological Investigation of Rheumatoid Arthritis case-control study (n = 2,871). Data on first- and second-degree relatives were obtained through the Swedish Multigeneration Register. Familial risks were calculated using conditional logistic regression.

RESULTS

Consistent across data sources, the familial odds ratio for RA was ∼3 in first-degree relatives of RA patients and 2 in second-degree relatives. Familial risks were similar among siblings, parents, and offspring. Familial aggregation was not modified by sex, but was higher in RA patients with early-onset disease and in RF/ACPA-positive RA patients. The observed familial risks were consistent with a heritability of ∼50% for ACPA-positive RA and ∼20% for ACPA-negative RA.

CONCLUSION

The pattern of risks suggests that familial factors influence RA in men and women equally and that these factors are of less importance for late-onset RA. Familial factors are more important for seropositive RA, but there is significant familial overlap between seropositive RA and seronegative RA. Even if the familial risk is assumed to be completely due to genetics, the observed risks suggest that heritability of RA is lower than previously reported, in particular for ACPA-negative RA.

On the origin of rheumatoid arthritis: the impact of environment and genes--a population based twin study

Background

Rheumatoid arthritis (RA) is an autoimmune disease with a complex origin. Previous studies have reported heritability estimates on RA at about 60%. Only 16% of the genetic background of the disease has been disclosed so far. The purpose of the present investigation was to provide an optimized estimate on the heritability of RA and to study the recurrence risk in a nationwide Caucasian twin population.

Methods and Findings

In a mail survey addressed to 56.707 twin individuals, RA was reported by 479 individuals, mean age 52 (range 16–73). Respondents underwent an interview and clinical examination. Ascertainment probability was 80%. RA was confirmed in 162 twin individuals yielding a prevalence at 0.37% (95% CI 0.31–0.43). The mean discordance time was 19 years (range 0–57). The concordance was 9.1% (95% CI 1.9 to 24.3) in MZ, 6.4% (95% CI 2.1 to 14.3) in DZss. The increased relative risk of attracting RA conditioned on having an affected cotwin compared to the background population risk was 24.6 to 35.4 in MZ twins and 17.3 to 31.6 in DZss twins. The correlation coefficients were 0.60 (0.33 to 0.78) in monozygotic (MZ) and 0.55 (0.33 to 0.72) in dizygotic same sexed (DZss) pairs. Twelve percent (95% CI 0–76%) of the phenotypic variance in the liability to RA was due to additive genetic effects, 50% (95% CI 0–72%) to shared environmental effects and 38% (95% CI 17–61%) to non-shared environmental effects.

Conclusions

This study emphasizes that family factors are important for the development of RA. Although genetic effectors are important, shared and non-shared environmental triggers and/or epigenetic stochastic events seem to be even more significant. However, it should be borne in mind that the genetic and non-genetic components may not be the same across disease subsets.

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 clustering of the serum cytokine profile in the relatives of rheumatoid arthritis patients

OBJECTIVE

Rheumatoid arthritis (RA) is prevalent in North American Native populations, with a high frequency of multicase families and seropositivity in first-degree relatives. This study was undertaken to determine whether the serum cytokine profile of first-degree relatives of North American Native patients with RA differed from that of individuals with no family history of autoimmunity and whether there was an association with RA autoantibodies.

METHODS

North American Native patients with RA (n = 105), their first-degree relatives (n = 273), healthy North American Native controls (n = 200), and Caucasian controls (n = 150) were studied. Serum levels of 42 cytokines were tested using a multiplex laser bead assay. Rheumatoid factor (RF), anti-cyclic citrullinated peptide 2 (anti-CCP-2), monocyte chemotactic protein 1 (MCP-l), and high-sensitivity C-reactive protein (hsCRP) were tested by enzyme-linked immunosorbent assay, and HLA-DRB1 alleles by specific primers. Discriminant analysis and logistic regression classified individuals based on their cytokine profile.

RESULTS

The prevalence of RF (cutoff level predetermined to include 5% of Caucasian controls) and anti-CCP (cutoff level of ≥40 units) was, respectively, 88% and 81% in the RA patients, 34% and 9% in first-degree relatives, and 9% and 4% in North American Native controls; the prevalence of anti-CCP was 0% in Caucasian controls. Levels of most cytokines were highest in RA patients; 17 of 40 cytokines (43%) were significantly higher in first-degree relatives than in controls, including multiple proinflammatory cytokines. Discriminant analysis showed a notable distinction between the groups, with 85% classification accuracy. First-degree relatives had markedly higher MCP-1 and hsCRP levels than North American Native controls, but there was no consistent association with RA autoantibodies.

CONCLUSION

Our findings indicate that levels of multiple cytokines and hsCRP are higher in first-degree relatives of North American Native patients with RA compared to individuals from a nonautoimmune background. These data suggest that elevated baseline cytokine levels may be part of the risk profile for developing RA.

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.

Classification of rheumatologic opinion on early inflammatory arthritis: harmonization of a heterogeneous standard

OBJECTIVE

Interrater variability limits rheumatologic opinion as a reference standard for early inflammatory arthritis (IA) classification. The study objectives were to determine whether rheumatologic opinion is associated with potential early IA classification methods despite high interrater variability, and to compare the relative strengths of those associations.

METHODS

Eighteen rheumatologists independently classified 30 initial rheumatology presentation summaries as early IA or not and recommended a pharmacotherapy. Case fulfillment of the following classification methods was independently determined: early referral to rheumatology recommendation for rheumatoid arthritis (ERRR), common early IA cohort inclusion criteria (CEAC), and prevalent IA classification criteria (American College of Rheumatology [ACR]/European Spondylarthropathy Study Group [ESSG]). Associations between rheumatologic opinion, disease-modifying antirheumatic drug (DMARD) recommendation, and each classification method were determined.

RESULTS

Participating rheumatologists published on early IA and represented 3 continents. The median case was age 43 (interquartile range [IQR] 30-53) years, had 40 (IQR 24-104) weeks of symptoms, 60 (IQR 18-120) minutes of morning stiffness, a swollen joint count of 6 (IQR 1-13), and an erythrocyte sedimentation rate of 25 (IQR 10-51) mm/hour. The mean ± SD multiple-rater kappa for rheumatologic opinion on early IA was 0.16 ± 0.02. The common odds ratios for associations between rheumatologic opinion and ERRR, CEAC, and ACR/ESSG were 10.3 (95% confidence interval [95% CI] 4.6-23.2), 4.4 (95% CI 2.5-7.7), and 0.7 (95% CI 0.4-1.1), respectively. Odds ratios for associations between DMARD recommendation and ERRR, rheumatologic opinion, CEAC, and ACR/ESSG were 18.7 (95% CI 8.1-43.2), 10.6 (95% CI 6.0-18.8), 2.8 (95% CI 1.7-4.6), and 0.5 (95% CI 0.3-0.7), respectively.

CONCLUSION

Classification methods can be used to harmonize rheumatologic opinion of early IA despite high interrater variability. The ERRR is very strongly associated with both rheumatologic opinions of early IA and DMARD treatment recommendations.

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.

The contribution of genetic variation and infection to the pathogenesis of ANCA-associated systemic vasculitis

The aetiology of anti-neutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis has not been well defined. Here we review two factors which may play a role in the pathogenesis of the disease: genetics and infection. In particular, we discuss the role of autoantibodies to LAMP-2, which may arise following infection with Gram-negative bacteria, and may contribute to the development of ANCA-associated systemic vasculitis in genetically susceptible individuals.

Risks and relative risks of Wegener's granulomatosis among close relatives of patients with the disease

OBJECTIVE

The etiology of Wegener's granulomatosis (WG) supposedly involves interplay between genetic susceptibility and environmental triggers. However, little is known about whether WG actually clusters in families. Information on the degree of familial aggregation in WG is of clinical relevance, because patients with WG often want to know whether their diagnosis puts their closest relatives at increased risk of the disease. The aim of this study was to investigate the risk of WG in relatives of patients with WG.

METHODS

Using Swedish nationwide registers on morbidity, family structure, and vital status, we compared the occurrence of WG (register-based plus chart review) among 6,670 first-degree relatives and 428 spouses of 1,944 Swedish patients with WG with the occurrence among 68,994 first-degree relatives and 4,812 spouses of 19,655 control subjects from the general population. Relative risks were estimated using the Cox proportional hazards regression model.

RESULTS

Two of the 6,670 first-degree relatives of patients with WG and 13 of the 68,994 first-degree relatives of their population controls had WG, resulting in a relative risk of 1.56 (95% confidence interval 0.35-6.90). None of the 428 spouses of patients had WG.

CONCLUSION

In absolute terms, the occurrence of WG among close biologic and nonbiologic relatives of patients with WG is low. In terms of relative risk, our results provide strong evidence against a pronounced increase in familial risk such as that noted for systemic lupus erythematosus, irritable bowel disease, and multiple sclerosis but are compatible with familial aggregation of a magnitude similar to that for rheumatoid arthritis.

Environmental epidemiology and risk factors for autoimmune disease

It has long been recognized that environmental influences play an important role in the risk of developing chronic rheumatic disease. Defining specific pathogenic environmental mediators that may trigger the development or progression of autoimmune disease remains a focus of increasing investigative effort. Factors promoting disease may not be identical to factors that influence the severity or progression of the disorder. Human monozygotic twin studies, animal studies, and genetic models demonstrate that genetic influences strongly determine whether one will develop autoimmunity, however, genes affecting the metabolism of exogenous agents that may trigger disease expression have only recently drawn attention. In this article the authors review recent reports that advance our understanding of previously recognized environmental risk factors and challenge accepted beliefs that increased estrogenic exposures predate the incidence of autoimmune disorders, systemic lupus erythematosus in particular.

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.

Clinical and immunogenetic characteristics of European multicase rheumatoid arthritis families

OBJECTIVE

To describe the characteristics of a new set of European families with affected sib pairs (ASP) collected by the European Consortium on Rheumatoid Arthritis Families (ECRAF) to replicate the results of our first genome scan. Potential gradients for disease severity in Europe and concordance within families were studied.

PATIENTS AND METHODS

From 1996 to 1998 European white families with at least two affected siblings were enrolled in the study. Demographic (sex, age at onset), clinical data (rheumatoid factor (RF), disease duration, erosive disease, extra-articular features (EF)), and HLA-DRB1 oligotyping were analysed.

RESULTS

565 patients with rheumatoid arthritis (RA), belonging to 271 families including 319 affected sib pairs (ASP) were collected. Belgium, France, Italy, the Netherlands, Portugal, and Spain contributed 20, 96, 52, 24, 9, and 70 families, respectively. Sex (78% women), age at onset (mean 44 years), and RF positivity (79%) were similar among the countries. Differences were found in disease duration (11-18 years) and in the prevalence of erosive disease (70-93%), nodules (15-44%), subjective Sjögren's syndrome (5-38%), and EF (3-16%) (p<0.05 in all cases). A total of 22% RA sibs were shared epitope (SE) negative, whereas 47% and 30% carried one and two SE alleles respectively. Carriage of SE differed widely among countries (p<0.0001): no SE alleles (6-36%), one allele (43-60%), and two alleles (20-39%). SE encoding alleles were mainly DRB1*04 in the Netherlands and Belgium, whereas SE carriage was less common and evenly distributed between DRB1*01, *04, and *10 in Mediterranean countries. No concordance within families was found either in age/calendar year of onset (intraclass correlation coefficient <0.50) or in clinical and radiological features (kappa<0.22).

CONCLUSIONS

The differences in RA characteristics between European countries and within families underline the heterogeneity of the disease. No clear cut gradient of disease severity was seen in Europe.

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 vs sporadic rheumatoid arthritis (RA). A prospective study in an early RA inception cohort

OBJECTIVES

To study potential differences in demographic, process and outcome variables between familial and sporadic rheumatoid arthritis (RA) in an early RA inception cohort.

METHODS

In 1998, we ascertained the familial status of all collaborative patients in a large early RA inception cohort at our department. Familial RA was defined by the presence of at least two siblings fulfilling the American College of Rheumatology criteria for RA. Baseline demographic data and prospectively recorded disease activity variables, therapies and radiological damage during the first 6 yr of disease were included in the analysis. A regression analysis was performed to assess whether familial clustering is a prognostic factor.

RESULTS

We identified 142 patients with sporadic and 36 with familial RA. The most striking difference between these groups was the larger sibship size in multicase families (8.2 +/- 2.5 vs 5. 5 +/- 2.8; P < 0.0001). Age at onset was similar in both groups, although males with familiar RA were younger at disease onset than those with sporadic RA (median 50 vs 57 yr; P=0.03). No differences were found in gender, presence of rheumatoid factor (RF), antinuclear factor and HLA-DR typing or in disease activity, interventions and outcome over 6 yr of follow-up. Early radiological damage and disease activity, but not familial history of RA were prognostic for X-ray damage.

CONCLUSION

We show that sibship size is the only relevant risk factor for familial RA. No differences in genotypic and phenotypic characteristics, disease severity or radiological damage were observed among familial and sporadic RA. Familial history of RA is not a poor prognostic factor. This prospective study confirms previous cross-sectional findings in the Dutch population.

[Clinical characteristics of familial rheumatoid arthritis in Spain. A study of 73 families. Spanish Consortium for Rheumatoid Arthritis (CEAR) and European Consortium for Familial Rheumatoid Arthritis (ECRAF)]

OBJECTIVE

To describe clinical characteristics and the homogeneity of disease expression between involved members in multicase Spanish rheumatoid arthritis (RA) families.

PATIENTS AND METHODS

73 families with two or more siblings with RA were found, with a total of 149 patients distributed in 79 pairs (70 sib pairs, and 3 sib trios). Demographic, clinical and radiological characteristics were recorded in a standard questionnaire.

RESULTS

Clinical characteristics were similar to those of sporadic RA with a high frequency of women (78%), positive rheumatoid factor (RF) (86%), erosions (89%) and a 25% of the patients having extraarticular disease. The most important variable in disease severity was disease duration. The concordance between family members of the same age and calendar year of disease onset, and the pattern of disease expression, was not higher than expected, showing that the disease is heterogenic.

CONCLUSION

Environmental factors seem to be more important in RA susceptibility. Clinical characteristics of familiar RA in Spain do not seem to be different from sporadic RA, although differences were found in disease expression within families that may be due to variation of genetic or environmental factors, responsible for the susceptibility and disease duration.

The role of genetic factors in autoimmune disease: implications for environmental research

Studies in both humans and in animal models of specific disorders suggest that polymorphisms of multiple genes are involved in conferring either a predisposition to or protection from autoimmune diseases. Genes encoding polymorphic proteins that regulate immune responses or the rates and extent of metabolism of certain chemical structures have been the focus of much of the research regarding genetic susceptibility. We examine the type and strength of evidence concerning genetic factors and disease etiology, drawing examples from a number of autoimmune diseases. Twin studies of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type I diabetes, and multiple sclerosis (MS) indicate that disease concordance in monozygotic twins is 4 or more times higher than in dizygotic twins. Strong familial associations (odds ratio ranging from 5-10) are seen in studies of MS, type I diabetes, Graves disease, discoid lupus, and SLE. Familial association studies have also reported an increased risk of several systemic autoimmune diseases among relatives of patients with a systemic autoimmune disease. This association may reflect a common etiologic pathway with shared genetic or environmental influences among these diseases. Recent genomewide searches in RA, SLE, and MS provide evidence for multiple susceptibility genes involving major histocompatibility complex (MHC) and non-MHC loci; there is also evidence that many autoimmune diseases share a common set of susceptibility genes. The multifactorial nature of the genetic risk factors and the low penetrance of disease underscore the potential influence of environmental factors and gene-environment interactions on the etiology of autoimmune diseases.