The challenge of early synovitis: multiple pathways to a common clinical syndrome
Arthritis Research & Therapy volume 1, Article number: 31 (1999)
Synovial inflammation involving one or more joints is the presenting feature, and often the predominant clinical manifestation of a spectrum of pathologic states, many of which continue to be incompletely understood. The outcome of early synovitis can range from rapid and complete resolution to a persistent inflammatory process associated with irreversible articular damage and progressive functional decline.
A rapidly expanding body of information generated from clinical, epidemiological, and basic research is providing a deeper understanding of how genetic susceptibility factors interact in complex ways with diverse environmental factors, resulting in seemingly related clinical syndromes. Such clinical syndromes can be thought of as 'phenocopies': in other words phenotypically similar, yet mechanistically distinct, states. Delineation of the specific molecular pathways that underlie disease expression is also linking highly distinct and seemingly unrelated clinical syndromes. These disorders are mechanistically similar, yet phenotypically distinct. These concepts are particularly relevant to understanding the spectrum of autoimmunity, chronic inflammation, and how they intersect to produce synovitis.
In attempting to understand more completely the mechanistic similarities and differences in patients with early synovitis, an increasing panoply of variables needs to be considered. Although, to date, no clear model has emerged upon which to classify early synovitis better, an understanding of how these variables interact and intersect will undoubtedly be of value in delineating the early synovitis phenocopies.
Clinical patterns and classification
In clinical practice, early synovitis is initially classified on the basis of the extent, location, and symmetry of the joint involvement. Although rheumatologists, as a group, are particularly skilled at this type of pattern recognition, the etiopathogenic mechanisms determining these patterns of joint involvement are unknown, and therefore the implications are empiric. Symmetrical involvement of the wrists and small joints of the hands and feet is highly characteristic of established rheumatoid arthritis (RA) and, when present at the onset of the synovitis, suggests the patient's symptoms will probably evolve into the typical RA phenotype, particularly if rheumatoid factor (RF) is present. The tendency for psoriatic arthritis to involve the distal interphalangeal joints of the hands, and to involve multiple joints of a single digit asymmetrically, is also used as an early classification feature, even in the absence of any obvious psoriatic plaques. The 'reactive arthritis' syndrome that in some individuals follows particular genitourinary and gastrointestinal infections typically features an asymmetric lower extremity oligoarthritis. Patients with this articular pattern are often labeled with this diagnosis, even if an antecedent infection cannot be identified. Features such as enthesitis, sacroiliitis, and dactylitis tend to cluster with this complex of articular inflammation, and collectively form an overall 'spondylarthropathy' pattern.
This informal pattern recognition has been formalized into criteria sets, which attempt to classify arthritis syndromes, although not necessarily on a mechanistic basis. The best validated and most widely used of these criteria sets are the 1987 American College of Rheumatology (ACR) RA criteria  and the 1991 European Spondylarthropathy Study Group (ESSG) spondylarthropathy criteria . These criteria sets were developed as a consensus of expert opinion around patients with well-established and characteristic clinical features. They are not well suited for classifying cohorts of early synovitis patients, particularly if the aim is to identify uniform groups that have a common pathogenic mechanism and predictable prognosis. Indeed, even within the context of what is generally accepted to be 'typical' RA, there is considerable genetic, pathologic, and immunologic heterogeneity.
Published data from early synovitis cohorts, including our own at the NIH, indicate that a large percentage of patients can only be labeled as having 'unclassified' or 'undifferentiated' arthritis [3,4,5,6]. In our cohort, approximately one-third of the patients who were evaluated within one year of symptom onset fell into this category, and in some series this has been as high as 50% [4,7]. It has been stated  that the term 'undifferentiated' could have any of the following implications: 1) an early stage of a well defined rheumatic disease that will later become differentiated; 2) an abortive form, or forme fruste, of a well defined rheumatic disease; 3) an overlap syndrome; or 4) a truly unknown, undefined disease that may be differentiated in the future. Of note, none of these classifications imply a pathogenic mechanism. The follow-up data that are available from early synovitis cohorts suggest that most of the undifferentiated patients remain undifferentiated, but in general tend to have a favorable prognosis with frequent remission [4,6].
Imaging in the evaluation of early synovitis
Radiographic imaging of articular and periarticular structures may contribute information that defines specific phenocopies more precisely. However, many of the findings such as soft tissue swelling, periarticular bone loss, new bone formation, and bone erosion may be non-specific. Moreover, the radiographic findings in patients with early synovitis are often subtle, confounding diagnostic categorization. In particular, establishing the unequivocal presence of erosions is notoriously difficult within the first year of synovitis. The insensitivity of plain radiography in detecting early erosions is evident when these techniques are compared to magnetic resonance imaging (MRI) [9,10,11,12]. Furthermore, in addition to detecting early erosions with a high degree of sensitivity, MRI is currently the only modality that clearly images the synovium, allowing the generation of quantitative data regarding synovial volume and perfusion [13,14,15,16,17]. These parameters are broadly indicative of the degree of synovial hyperplasia, infiltration, and proliferation. Longitudinal studies of inflamed RA joints have shown that the measurement of synovial volume using gadolinium-enhanced MRI is of value in predicting the subsequent development and progression of articular erosions [17,18]. This result tends to confirm the clinical impression that RA joints with a 'boggy', thickened synovium often undergo progressive damage.
MRI has been applied to the task of defining subsets of early synovitis patients on the basis of the distribution pattern of the inflammation [19,20,21]. The data suggest two principal imaging patterns, one where the inflammatory changes are based primarily in the synovium, and another where the periarticular entheses are inflamed in association with intense edema of the adjacent bone. These two patterns are proposed to broadly classify patients with early synovitis into an 'RA' phenotype where synovitis is the primary process, and a 'spondylarthropathy' phenotype where enthesitis is the primary process, and synovitis occurs on a secondary basis. Although the simplicity of this paradigm is conceptually appealing, it remains to be seen whether such a 'tidy' model will be of value in classifying the heterogeneous spectrum of patients seen in early synovitis clinics. It is also not clear whether these MRI patterns are based on distinct pathogenic mechanisms, as has been suggested . Interestingly, the limited data available regarding entheseal pathology suggest a relative paucity of inflammatory features histologically, a finding which may itself hint at a unique pathologic process in these structures.
In view of the widely divergent outcomes associated with early synovitis, it has been assumed that specific pathologic features, or constellations of pathologic features, can be identified in early synovial tissue samples. Identification of these features would allow the definition of distinct pathogenic mechanisms, and in turn, the definition of unique phenocopies. The pursuit of this hypothesis has been facilitated by the more widespread use of closed needle biopsy and needle arthroscopy techniques. Several centers, including our own, have undertaken extensive studies of early synovial tissue samples, taken soon after the onset of the synovitis, which are analyzed using a variety of histological and molecular pathology techniques. The patients are then followed longitudinally, and the pathologic data is related to outcomes. Although many of these initiatives are still in progress, the published data do not suggest major differences between early RA synovitis and other forms of early synovitis, or even between early and late synovitis [22,23,24]. The prominence of plasma cells and macrophages at all stages of RA synovitis has been noted [25,26,27]. Indeed, recent data suggest that synovial macrophage infiltration may occur at a very early, possibly preclinical, stage in RA , and that the degree of macrophage infiltration may ultimately be an indicator of the erosive potential of the synovitis [26,27]. Consistent with this view is mounting evidence that osteoclasts, the precursors of which are myeloid cells, are likely to be important mediators of bone erosion . It can be speculated that the identification of synovial microenvironments which promote pathways leading to the differentiation of large numbers of myeloid cells into osteoclasts would be an important step towards defining an erosive synovial phenotype pathologically. At present there is little experimental evidence in this regard.
Synovitis is clearly associated with a wide spectrum of infectious agents, and the mechanisms underlying this association are varied and complex. In the case of septic arthritis, arguably the best understood of these associations, a pathogen gains access to the usually sterile synovial cavity, precipitating an acute monoarticular synovitis which is predominated by polymorphonuclear leukocytes, and which is rapidly destructive. Viable organisms are directly demonstrable in the synovial fluid or tissue, and the inflammatory process usually resolves completely with the prompt and successful eradication of the organism. In general, genetic elements do not appear to play a major role in the susceptibility to most forms of septic arthritis, although this has not been extensively studied.
Lyme arthritis is frequently in the differential diagnosis in patients with early synovitis, particularly in endemic areas. This disorder has been a good model for understanding the mechanisms by which microorganisms can interact with the host's immune responses to precipitate and perpetuate synovitis. Borrelia burgdorferi spirochetes have been demonstrated in synovial tissue samples obtained early in the disease, and PCR techniques have further enhanced the early detection of this organism in synovial tissue and fluid [30,31,32,33,34]. The chronic arthropathy, typically affecting a single knee joint, is more suggestive of a persistent local immune response to bacterial antigens than of a chronic infectious process. Furthermore, this syndrome demonstrates an association with HLA-DR4. The histopathologic features of chronic Lyme synovitis can be indistinguishable from those of RA , although we have observed that Lyme synovitis tends to feature extensive stromal fibrin deposits. Of considerable scientific interest has been the recent observation that individuals with persistent, treatment-resistant Lyme arthritis demonstrate specific T cell responses to endogenous lymphocyte function associated antigen (LFA)-1 sequences that are homologous to sequences in the OSP-A outer membrane protein of Borrelia burgdorferi . This apparent molecular mimicry illustrates the degree of complexity inherent in the mechanisms by which microorganisms interact with the host to cause a persistent inflammatory lesion in the synovium.
The complex interplay between pathogen and host, which can whimsically be termed 'the battle of the genomes', is particularly relevant to reactive arthritis. In this intriguing clinical syndrome, there is a clear association with specific pathogens...sometimes, a clear genetic predilection...sometimes, and complete resolution of the synovitis...most of the time. In well characterized cases, a lower extremity asymmetric synovitis, variably associated with enthesitis and sacroiliitis, typically follows a genitourinary or gastrointestinal infectious syndrome after 2–4 weeks. Yet only a minority of patients with this pattern of early synovitis have demonstrable organisms in their urogenital or gastrointestinal tract. Many are labeled as having undifferentiated arthritis. On the other hand, detailed studies of synovial samples from the NIH early synovitis cohort have demonstrated the presence of Chlamydia trachomatis (CT) DNA, RNA, and antigens, not only in the synovium of patients with 'typical' reactive arthritis, but also in a spectrum of other synovial tissues, including samples from patients with RF-positive RA, and even in apparently healthy individuals [37,38]. In this cohort, synovial cytokine expression profiles assessed using a nested reverse transcriptase polymerase chain reaction (RT PCR) technique  failed to confirm the comparatively high interleukin (IL)-4 levels in the synovium of reactive arthritis patients that were previously reported . In agreement with the previous studies, they did indicate that the synovium of patients with early CT reactive arthritis, in contrast to that of undifferentiated arthritis patients with a similar clinical pattern but no synovial CT, exhibits high levels of both interferon (IFN)-γ and IL-10 [41,42]. Such a cytokine profile has been speculated to play a role in attenuating the expression of specific CT genes such as MOMP, while promoting the expression of other genes such as hsp60 [43,44]. Ultimately, this may result in ineffective elimination of the pathogen.
Interest in a bacterial or viral etiology for RA continues to wax and wane. Particularly provocative have been recent studies indicating the presence of parvovirus B19 and Epstein-Barr virus (EBV) DNA, RNA, and antigens, specifically in the synovium of RA patients [45,46]. In the case of EBV, this was highly associated with DR4 encoding shared epitope alleles, suggesting an important immunogenetic link. As these studies were performed primarily on synovial samples from patients with long-standing disease, it would be quite instructive to verify the findings in heterogeneous early synovitis cohorts. It is possible that, rather than being specific etiologic agents, these viruses are involved in the persistence of the synovitis once it is established.
It has recently been recognized that, in addition to RF, a number of antigen-autoantibody systems are highly specific for RA, and may be of importance both pathogenetically and prognostically . These systems include the antifilaggrin (AFA), antikeratin (AKA), antiperinuclear factor (APF) group, all of which appear to relate to the presence of citrulline residues in target antigens . Anti-Sa antibodies, also highly specific for RA, identify an unknown 50 kDa antigen (called Sa) which is present in the synovium, and may also be citrullinated . Antibodies directed against the protease inhibitor calpastatin (Ra-1) have been shown to be common in RA sera , as have antibodies directed toward advanced-glycation-endproduct-modified immunoglobulin G (AGE-IgG) . Ra-33 is directed towards a spliceosomal ribonucleoprotein, and is detectable in RA, systemic lupus erythematosus (SLE), and mixed connective tissue disease (MCTD) patients . Approximately 10–15% of RA patients demonstrate antibodies to native collagen II, although these antibodies are not specific to this arthropathy .
Several groups are currently evaluating the diagnostic and prognostic significance of these autoantibodies in cohorts of patients with early synovitis. The preliminary findings from our cohort confirm a strong association of antifilaggrin and anti-Sa antibodies with RF-positive polyarthritis, although we identified a number of patients with RF-negative synovitis, both poly and oligoarticular, who were also positive for these two antibodies. Moreover, it appears that anti-Sa antibodies may be associated with a subset of patients having more severe, erosive RA .
Studies evaluating genetic association with rheumatic diseases have generally been carried out in populations of patients with well established, well characterized clinical syndromes. In the case of RA, the association is based principally in the class II region of the major histocompatibility complex (MHC), a group of at least 50 genes on human chromosome 6 that encode cell-surface proteins and that are involved in the immune response to both self and nonself antigens. The genetic association has been best explained by the shared epitope (SE) hypothesis . In this model, disease susceptibility and/or severity is based on the presence of a shared epitope, the QK(R)RAA amino acid residue sequence in the third hypervariable region of the DRβ 1 molecule. The SE sequence is present in a number of DRB1 alleles, all of which have been individually and collectively associated with typical RF-positive RA. Furthermore, there appears to be an allele dosage effect, particularly in respect to disease severity . We have found that the SE alleles, particularly DRB1*0401, are clearly over-represented in patients with early RF-positive polyarthritis compared to both other patients with early synovitis and normal controls . Moreover, we detect a high degree of association between SE alleles and the presence of anti-Sa and antifilaggrin antibodies . Interestingly, we were able to show an association between SE and the presence of early erosions in patients with RF-negative, but not RF-positive polyarthritis. Similar data have been generated from the Norfolk Arthritis Registry (Silman A, personal communication).
Based on elegant transgenic animal models , an alternative hypothesis has been proposed to explain the MHCclass II RA association . This hypothesis suggests that RA disease susceptibility actually relates to DQ locus alleles, and that this susceptibility is modified by the absence of protective (non-SE) DRB1 alleles. The model, which is harmonious with models of genetic susceptibility to type I diabetes, has recently been tested in two European RA populations and found to be a good fit with the epidemiologic data , but was not confirmed in another European study . Analysis of the data from our early synovitis cohort supports this model, although issues of linkage dysequilibrium continue to be problematic in these analyses. These issues have been raised in the context of several other MHC associations, including those relating to the tumor necrosis factor (TNF)-α gene.
There is a high degree of association between specific subtypes of HLA-B27 and the heterogeneous clinical spectrum of the 'spondylarthropathies'. It is not yet clear how disorders such as ankylosing spondylitis, reactive arthritis, and psoriatic arthritis are related pathogenetically, and what role B27 plays in these mechanisms. The association with axial manifestations such as sacroiliitis and spondylitis is particularly strong in all of these conditions. Our own data indicate that B27 is increased in the entire spectrum of early synovitis, including up to 20% of patients with RF-positive polyarthritis, a finding that has been previously reported in a Finnish RA cohort [61,62]. Moreover, we identified a significant association between B27 and SE alleles in the patients but not in a control population. These observations point to complex genetic interactions potentially involving extended 'arthritogenic' haplotypes, rather than associations of individual MHC alleles with specific forms of arthritis. The complexity of the genetic associations has been recently pointed out in experimental arthritis models where disease susceptibility, severity, and chronicity were each shown to be determined by entirely different regions in the genome [63,64].
Towards a mechanistically based prognostic model
As data from longitudinal studies of early synovitis cohorts are gathered, the relative importance of candidate prognostic variables is being clarified. The initial clinical patterns, autoantibody profiles, synovial pathologic features, cytokine profiles, and gene polymorphisms, among many other variables, represent variables that are being tested in robust multivariate models. In addition, the underlying mechanisms which potentially link these diverse variables are being explored, both in humans and in animal models. Ultimately, both the biological and statistical models aim to define homogeneous patient subsets to which targeted therapeutic paradigms can be applied. The definition of meaningful outcomes continues to be challenging, and recently there has been a shift towards using ambitious outcome measures such as the achievement of complete remission, the prevention rather than retardation of erosive damage, and the maintenance of normal function.
Currently, there is general agreement that the majority of patients who present with RF-positive symmetrical polyarthritis will probably go on to have persistent, erosive synovitis associated with a variable degree of disability. These patients are being targeted for early aggressive therapies. On the other hand, there is less certainty about the prognosis of RF-negative polyarthritis. At present it is not known whether there are common risk factors for bone erosion that link RF-positive RA, psoriatic arthritis, and subsets of RF-negative polyarthritis. On the basis of our own data, and data from other early synovitis cohorts, it can be proposed that in patients with early RF-negative polyarthritis, the presence of an RA-associated autoantibody such as anti-Sa, antifilaggrin, or anticitrulline, and/or the presence of one or more SE alleles, is an important indicator of erosive potential and an unfavorable prognosis. These variables can be used to allocate subsets of RF-negative polyarthritis patients to the same aggressive therapeutic strategies proposed for RF-positive patients.
Patients who present with oligoarthritis, in general, have the highest rates of complete resolution of synovitis within the first months after symptom onset, irrespective of whether they are labeled as having reactive arthritis or undifferentiated arthritis. There has been some suggestion that the presence of HLA-B27 in this group of patients is associated with more persistent synovitis, although the risk factors for erosive disease remain entirely unclear. It is possible that the presence of bacterial antigens or bacterial DNA transcripts in the synovium is a persistence factor. If indeed this is the case, this group of patients is the best suited for early synovial biopsy and a broad-based search for microbial antigens and transcripts in the synovium [65,66]. Despite the fact that most antibiotic trials of chronic reactive arthritis have been disappointing so far, there are little data available regarding how the effects of antimicrobial therapy may relate to the presence of bacterial antigens and transcripts in the synovium.
There is an increasing recognition that patients with synovitis of recent onset have divergent pathogenic mechanisms underlying what appear to be relatively similar clinical phenotypes. There is also a recognition that there are major differences in the outcome of early synovitis. The challenge facing investigators in this area is clarifying how these mechanisms determine outcome and, in turn, which mechanisms are the most appropriate therapeutic targets.
Arnett FC, Edworthy SM, Bloch DA, et al: The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis. Arthritis Rheum. 1988, 31: 315-324.
Dougados M, van der Linden S, Juhlin R, et al: The European Spondylarthropathy Study Group preliminary criteria for the classification of spondylarthropathy. Arthritis Rheum. 1991, 34: 1218-1227.
El-Gabalawy HS, Goldbach-Mansky R, Smith D, et al: Association of HLA alleles and clinical features in patients with synovitis of recent onset. Arthritis Rheum. 1999, 42: 1696-1705.
Hulsemann JL, Zeidler H: Undifferentiated arthritis in an early synovitis out-patient clinic. Clin Exp Rheumatol. 1995, 13: 37-43.
Harrison BJ, Symmons DM, Brennan P, et al: Inflammatory polyarthritis in the community is not a benign disease: predicting functional disability one year after presentation. J Rheumatol . 1996, 23: 1326-1331.
Wolfe F, Ross K, Hawley DJ, Roberts FK, Cathey MA: The prognosis of rheumatoid arthritis and undifferentiated polyarthritis syndrome in the clinic: a study of 1141 patients. J Rheumatol. 1993, 20: 2005-2009.
Hulsemann JL, Zeidler H: Diagnostic evaluation of classification criteria for rheumatoid arthritis and reactive arthritis in an early synovitis outpatient clinic. Ann Rheum Dis. 1999, 58: 278-280.
Wollenhaupt J, Zeidler H: Undifferentiated arthritis and reactive arthritis. Curr Opin Rheumatol. 1998, 10: 306-313.
Foley-Nolan D, Stack JP, Ryan M, et al: Magnetic resonance imaging in the assessment of rheumatoid arthritis: a comparison with plain film radiographs. Br J Rheumatol. 1991, 30: 101-106.
Forslind K, Larsson EM, Johansson A, Svensson B: Detection of joint pathology by magnetic resonance imaging in patients with early rheumatoid arthritis. Br J Rheumatol. 1997, 36: 683-638.
McQueen FM, Stewart N, Crabbe J, et al: Magnetic resonance imaging of the wrist in early rheumatoid arthritis reveals a high prevalence of erosions at four months after symptom onset. Ann Rheum Dis. 1998, 57: 350-356.
Jorgensen C, Cyteval C, Anaya JM, Baron MP, Lamarque JL, Sany J: Sensitivity of magnetic resonance imaging of the wrist in very early rheumatoid arthritis. Clin Exp Rheumatol. 1993, 11: 163-168.
Jevtic V, Watt I, Rozman B, et al: Contrast enhanced Gd-DTPA magnetic resonance imaging in the evaluation of rheumatoid arthritis during a clinical trial with DMARDs. A prospective two-year follow-up study on hand joints in 31 patients. Clin Exp Rheumatol. 1997, 15: 151-156.
Oliver C, Speake S, Watt I, Dieppe P, Ratcliffe G: Advantages of an increased dose of MRI contrast agent for enhancing inflammatory synovium. Clin Radiol. 1996, 51: 487-493.
Ostergaard M, Stoltenberg M, Lovgreen-Nielsen P, Volck B, Jensen CH, Lorenzen I: Magnetic resonance imaging-determined synovial membrane and joint effusion volumes in rheumatoid arthritis and osteoarthritis: comparison with the macroscopic and microscopic appearance of the synovium. Arthritis Rheum. 1997, 40: 1856-1867.
Ostergaard M, Stoltenberg M, Lovgreen-Nielsen P, Volck B, Sonne-Holm S, Lorenzen I: Quantification of synovistis by MRI: correlation between dynamic and static gadolinium-enhanced magnetic resonance imaging and microscopic and macroscopic signs of synovial inflammation. Magn Reson Imaging. 1998, 16: 743-754.
Ostergaard M, Hansen M, Stoltenberg M, et al: Magnetic resonance imaging-determined synovial membrane volume as a marker of disease activity and a predictor of progressive joint destruction in the wrists of patients with rheumatoid arthritis. Arthritis Rheum. 1999, 42: 918-929.
Jevtic V, Watt I, Rozman B, et al: Prognostic value of contrast enhanced Gd-DTPA MRI for development of bone erosive changes in rheumatoid arthritis. Br J Rheumatol. 1996, 35 (suppl 3): 26-30.
Jevtic V, Watt I, Rozman B, Kos-Golja M, Demsar F, Jarh O: Distinctive radiological features of small hand joints in rheumatoid arthritis and seronegative spondyloarthritis demonstrated by contrast-enhanced (Gd-DTPA) magnetic resonance imaging. Skeletal Radiol. 1995, 24: 351-355.
McGonagle D, Gibbon W, O'Connor P, Green M, Pease C, Emery P: Characteristic magnetic resonance imaging entheseal changes of knee synovitis in spondylarthropathy. Arthritis Rheum. 1998, 41: 694-700.
McGonagle D, Gibbon W, Emery P: Classification of inflammatory arthritis by enthesitis. Lancet. 1998, 352: 1137-1140.
Tak PP, Smeets TJ, Daha MR, et al: Analysis of the synovial cell infiltrate in early rheumatoid synovial tissue in relation to local disease activity. Arthritis Rheum. 1997, 40: 217-225.
Tak PP, Smeets TJM, Boyle DL, et al: p53 overexpression in synovial tissue from patients with early and longstanding rheumatoid arthritis compared with patients with reactive arthritis and osteoarthritis. Arthritis Rheum. 1999, 42: 948-953.
Thurkow EW, VanDerHeijden IM, Breedveld FC, et al: Increased expression of IL-15 in the synovium of patients with rheumatoid arthritis compared with patients with Yersinia induced arthritis and osteoarthritis. J Pathol. 1997, 181: 444-450. 10.1002/(SICI)1096-9896(199704)181:4<444::AID-PATH778>3.0.CO;2-O.
Smeets TJM, Dolhain RJEM, Breedveld FC, Tak PP: Analysis of the cellular infiltrates and expression of cytokines in synovial tissue from patients with rheumatoid arthritis and reactive arthritis. J Pathol. 1998, 186: 75-81. 10.1002/(SICI)1096-9896(199809)186:1<75::AID-PATH142>3.0.CO;2-B.
Mulherin D, Fitzgerald O, Bresnihan B: Synovial tissue macrophage populations and articular damage in rheumatoid arthritis. Arthritis Rheum. 1996, 39: 115-124.
Bresnihan B: Pathogenesis of joint damage in rheumatoid arthritis. J Rheumatol. 1999, 26: 717-719.
Kraan MC, Versendaal H, Jonker M, et al: Asymptomatic synovitis precedes clinically manifest arthritis. Arthritis Rheum . 1998, 41: 1481-1488.
Gravallese EM, Harada Y, Wang JT, Gorn AH, Thornhill TS, Goldring SR: Identification of cell types responsible for bone resorption in rheumatoid arthritis and juvenile rheumatoid arthritis. Am J Pathol. 1998, 152: 943-951.
Nanagara R, Duray PH, Schumacher HR: Ultrastructural demonstration of spirochetal antigens in synovial fluid and synovial membrane in chronic Lyme disease: possible factors contributing to persistence of organisms. Hum Pathology. 1996, 27: 1025-1034.
van der Heijden IM, Wilbrink B, Rijpkema SGT, et al: Detection of Borrelia burgdorferi sensu stricto by reverse line blot in the joints of Dutch patients with lyme arthritis. Arthritis Rheum. 1999, 42: 1473-1480.
priem S, Burmester GR, Kamradt T, Wolbart K, Rittig MG, Krause A: Detection of Borrelia burgdorferi by polymerase chain reaction in synovial membrane, but not in synovial fluid from patients with persisting Lyme arthritis after antibiotic therapy. Ann Rheum Dis. 1998, 57: 118-121.
Jaulhac B, CharyValckenaere I, Sibilia J, et al: Detection of Borrelia burgdorferi by DNA amplification in synovial tissue samples from patients with Lyme arthritis. Arthritis Rheum. 1996, 39: 736-745.
Nocton JJ, Dressler F, Rutledge BJ, Rys PN, Persing DH, Steere AC: Detection of Borrelia burgdorferi DNA by polymerase chain reaction in synovial fluid from patients with Lyme arthritis. New Engl J Med. 1994, 330: 229-234.
Steere AC, Duray PH, Butcher EC: Spirochetal antigens and lymphoid-cell surface markers in Lyme synovitis: comparison with rheumatoid synovium and tonsillar lymphoid tissue. Arthritis Rheum. 1988, 31: 487-495.
Gross DM, Forsthuber T, Tary-Lehmann M, et al: Identification of LFA-1 as a candidate autoantigen in treatment-resistant Lyme arthritis. Science. 1998, 281: 703-706. 10.1126/science.281.5377.703.
Schumacher HR, Arayssi T, Crane M, et al: Chlamydia trachomatis nucleic acids can be found in the synovium of some asymptomatic subjects. Arthritis Rheum . 1999, 42: 1281-1284.
Goldbach-Mansky R, Hudson A, Gerard H, et al: Does the presence of C-trachomatis in synovial tissue correlate with immune serology and outcome in recent onset synovitis?. Arthritis Rheum. 1998, 41: S148-S148.
Kotake S, Schumacher HR, Yarboro CH, et al: In vivo gene expression of type 1 and type 2 cytokines in synovial tissues from patients in early stages of rheumatoid, reactive, and undifferentiated arthritis. Proc Assoc Am Physicians. 1997, 109: 286-301.
Simon AK, Seipelt E, Sieper J: Divergent T-cell cytokine patterns in inflammatory arthritis. Proc Natl Acad Sci U S A. 1994, 30: 8562-8566.
Kotake S, Schumacher HR, Arayssi TK, et al: Gamma interferon and interleukin-10 gene expression in synovialtissues from patients with early stages of Chlamydia associated arthritis and undifferentiated oligoarthritis and from healthy volunteers. Infect Immun. 1999, 67: 2682-2686.
Kotake S, Schumacher HR, Yarboro CH, et al: In vivo, gene expression of type 1 and type 2 cytokines in synovial tissues from patients in early stages of rheumatoid, reactive, and undifferentiated arthritis. Proc Assoc Am Physicians . 1997, 109: 286-301.
Gerard HC, Branigan PJ, Schumacher HR, Hudson AP: SynovialChlamydia trachomatis in patients with reactive arthritis Reiter's syndrome are viable but show aberrant gene expression. J Rheumatol. 1998, 25: 734-742.
Nanagara R, Li F, Beutler A, Hudson A, Schumacher HRJ: Alteration of Chlamydia trachom atis biologic behavior in synovial membranes. Suppression of surface antigen production in reactive arthritis and Reiter's syndrome. Arthritis Rheum. 1995, 38: 1410-417.
Takahashi Y, Murai C, Shibata S, et al: Human parvovirus B19 as a causative agent for rheumatoid arthritis. Proc Natl Acad Sci USA. 1998, 95: 8227-8232.
Saal JG, Krimmel M, STEIDLE M, et al: Synovial Epstein-Barr virus infection increases the risk of rheumatoid arthritis in individuals with the shared HLA-DR4 epitope. Arthritis Rheum. 1999, 42: 1485-1496.
Menard HA, El Amine M, Despres N: Rheumatoid arthritis associated autoimmune systems. J Rheumatol. 1998, 25: 835-837.
Schellekens GA, de Jong BAW, Van den Hoogen FHJ, Van de Putte LBA, Van Venrooij WJ: Citrulline is an essential constituent of antigenic determinants recognized by rheumatoid arthritis-specific autoantibodies. J Clin Invest. 1998, 101: 273-281.
Despres N, Boire G, Lopezlongo FJ, Menard HA: The Sa system: a novel antigen-antibody system specific for rheumatoid arthritis. J Rheumatol. 1994, 21: 1027-1033.
Despres N, Talbot G, Plouffe B, Boire G, Menard HA: Detection and expression of a cDNA clone that encodes a polypeptide containing 2 inhibitory domains of human calpastatin and its recognition by rheumatoid arthritis sera. J Clin Invest. 1995, 95: 1891-1896.
Ligier S, Fortin PR, Newkirk MM: A new antibody in rheumatoid arthritis targeting glycated IgG: IgM anti-IgG-AGE. Br J Rheumatol. 1998, 37: 1307-1314.
Skriner K, Sommergruber WH, Tremmel V, Fischer I, Barta A, Smolen JS, Steiner G: Anti-A2/RA33 autoantibodies are directed to the RNA binding region of the A2 protein of the heterogeneous nuclear ribonucleoprotein complex. Differential epitope recognition in rheumatoid arthritis, systemic lupus erythematosus, and mixed connective tissue disease. J Clin Invest. 1997, 100: 127-135.
Terato K, DeArmey DA, Ye XJ, Griffiths MM, Cremer MA: The mechanism of autoantibody formation to cartilage in rheumatoid arthritis: possible cross-reaction of antibodies to dietary collagens with autologous type II collagen. Clin Immunol Immunopathol. 1996, 79: 142-154. 10.1006/clin.1996.0061.
Goldbach-Mansky R, Hoxworth J, Lee J, et al: RA associated autoantibodies define subsets of patients with early synovitis. Arthritis Rheum. 1999, 42 (suppl): S128-
Gregersen PK, Silver J, Winchester RJ: The shared epitope hypothesis: an approach to understanding the molecular-genetics of susceptibility to rheumatoid arthritis. Arthritis Rheum. 1987, 30: 1205-1213.
Weyand CM, Hicok KC, Conn DL, Goronzy JJ: The influence of HLA-DRB1 genes on disease severity in rheumatoid arthritis. Ann Intern Med. 1992, 117: 801-806.
Nabozny GH, Baisch JM, Cheng S, et al: HLA-DQ8 transgenic mice are highly susceptible to collagen-induced arthritis: a novel model for human polyarthritis. J Exp Med. 1996, 183: 27-37.
Zanelli E, Gonzalez-Gay MA, David CS: Could HLA-DRB1 be the protective locus in rheumatoid arthritis?. Immunol Today. 1995, 16: 274-278.
van der Horst-Bruinsma IE, Visser H, Hazes JMW, et al: HLA-DQ-associated predisposition to and dominant HLA-DR-associated protection against rheumatoid arthritis. Hum Immunol. 1999, 60: 152-158.
De Vries N, van Elderen C, Tijssen H, van Riel PLCM, Van de Putte LBA: No support for HLA-DQ encoded susceptibility in rheumatoid arthritis. Arthritis Rheum. 1999, 42: 1621-1627.
Ilonen J, Hakala M, Reijonen H, Tiilikainen A: B27-bearing HLA haplotypes in rheumatoid arthritis: characterization in Finnish patients. Hum Immunol. 1991, 30: 7-10.
Paimela L, Leirisalorepo M, Helve T, Koskimies S: The prognostic value of HLA-DR4 and HLA-B27 antigens in early rheumatoid arthritis. Scand J Rheumatol. 1993, 22: 220-224.
Yang HT, Jirholt J, Svensson L, et al: Identification of genes controlling collagen-induced arthritis in mice: striking homology with susceptibility loci previously identified in the rat. J Immunol. 1999, 163: 2916-2921.
Vingsbo-Lundberg C, Nordquist N, Olofsson P, et al: Genetic control of arthritis onset, severity and chronicity in a model for rheumatoid arthritis in rats. Nature Genet. 1998, 20: 401-404.
Wilkinson NZ, Kingsley GH, Jones HW, Sieper J, Braun J, Ward ME: The detection of DNA from a range of bacterial species in the joints of patients with a variety of arthritides using a nested, broad-range polymerase chain reaction. Rheumatology. 1999, 38: 260-266. 10.1093/rheumatology/38.3.260.
Wilbrink B, van der Heijden IM, Schouls LM, et al: Detection of bacterial DNA in joint samples from patients with undifferentiated arthritis and reactive arthritis, using polymerase chain reaction with universal 16S ribosomal RNA primers. Arthritis Rheum . 1998, 41: 535-543.
About this article
Cite this article
El-Gabalawy, H. The challenge of early synovitis: multiple pathways to a common clinical syndrome. Arthritis Res Ther 1, 31 (1999). https://doi.org/10.1186/ar8
- Rheumatoid Arthritis
- Chlamydia Trachomatis
- Reactive Arthritis
- Shared Epitope