Juvenile idiopathic arthritis genetics - what's new? What's next?

[Periodontal disease in pediatric rheumatic diseases]

Gingivitis and periodontitis are immunoinflammatory periodontal diseases characterized by chronic localized infections usually associated with insidious inflammation This narrative review discusses periodontal diseases and mechanisms influencing the immune response and autoimmunity in pediatric rheumatic diseases (PRD), particularly juvenile idiopathic arthritis (JIA), childhood-onset systemic lupus erythematosus (C-SLE) and juvenile dermatomyositis (JDM). Gingivitis was more frequently observed in these diseases compared to health controls, whereas periodontitis was a rare finding. In JIA patients, gingivitis and periodontitis were related to mechanical factors, chronic arthritis with functional disability, dysregulation of the immunoinflammatory response, diet and drugs, mainly corticosteroids and cyclosporine. In C-SLE, gingivitis was associated with longer disease period, high doses of corticosteroids, B-cell hyperactivation and immunoglobulin G elevation. There are scarce data on periodontal diseases in JDM population, and a unique gingival pattern, characterized by gingival erythema, capillary dilation and bush-loop formation, was observed in active patients. In conclusion, gingivitis was the most common periodontal disease in PRD. The observed association with disease activity reinforces the need for future studies to determine if resolution of this complication will influence disease course or severity.

TNF-α Polymorphisms in Juvenile Idiopathic Arthritis: Which Potential Clinical Implications?

Whether tumor necrosis factor alpha (TNF-α) gene polymorphisms (SNPs) influence disease susceptibility and treatment of patients with juvenile idiopathic arthritis (JIA) is presently uncertain. TNF-α is one of the most important cytokine involved in JIA pathogenesis. Several single nucleotide polymorphisms (SNPs) have been identified within the region of the TNF-α gene but only a very small minority have proven functional consequences and have been associated with susceptibility to JIA. An association between some TNF-α SNPs and adult rheumatoid arthritis (RA) susceptibility, severity and clinical response to anti-TNF-α treatment has been reported. The most frenquetly studied TNF-α SNP is located at -308 position, where a substitution of the G allele with the rare A allele has been found. The presence of the allele -308A is associated to JIA and to a poor prognosis. Besides, the -308G genotype has been associated with a better response to anti-TNF-α therapy in JIA patients, confirming adult data. Psoriatic and oligoarticular arthritis are significantly associated to the -238 SNP only in some works. Studies considering other SNPs are conflicting and inconclusive. Large scale studies are required to define the contribution of TNF-α gene products to disease pathogenesis and anti-TNF-α therapeutic efficacy in JIA.

The pathogenesis of oligoarticular/polyarticular vs systemic juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) has had a long and difficult problem with classification. It is clearly a heterogeneous and multi-factorial autoimmune disease but all too often the distinctions among subtypes were unclear. In fact, there is now increasing evidence of a distinct pathogenesis of oligo/polyarticular JIA compared to systemic JIA. Oligo/polyarticular JIA is an antigen-driven lymphocyte-mediated autoimmune disease with abnormality in the adaptive immune system. Cartilage-derived auto-antigens activate autoreactive T cells including Th1 and Th17 cells with production of pro-inflammatory cytokines IFN-γ and IL-17. On the other hand, the inhibition of regulatory T (Treg) cells including natural Foxp3(+) Treg and self-heat shock protein-induced Treg cells with decreased anti-inflammatory cytokine IL-10 results in the loss of immune tolerance. Imbalance between autoreactive Th1/Th17 and Treg cells leads to the failure of T cell tolerance to self-antigens, which contributes to the synovial inflammation of oligo/polyarticular JIA. By contrast, systemic JIA is an autoinflammatory disease with abnormality in the innate immune system. A loss of control of the alternative secretory pathway leading to aberrant activation of phagocytes including monocytes, macrophages and neutrophils seems to be involved in the release of pro-inflammatory cytokines IL-1, IL-6, IL-18 and pro-inflammatory S100-proteins, which contribute to the multisystem inflammation of systemic JIA. Markedly distinct pathogenesis of oligo/polyarticular JIA and systemic JIA implies that they might need different treatment strategies.

Pathogenesis and clinical manifestations of juvenile rheumatoid arthritis

Juvenile rheumatoid arthritis (JRA) is the most common rheumatic childhood disease; its onset is before 16 years of age and it persists for at least 6 weeks. JRA encompasses a heterogeneous group of diseases that is classified according to 3 major presentations: oligoarthritis, polyarthritis, and systemic onset diseases. These presentations may originate from the same or different causes that involve interaction with specific immunogenetic predispositions, and result in heterogeneous clinical manifestations. An arthritic joint exhibits cardinal signs of joint inflammation, such as swelling, pain, heat, and loss of function; any joint can be arthritic, but large joints are more frequently affected. Extra-articular manifestations include high fever, skin rash, serositis, and uveitis. The first 2 types of JRA are regarded as T helper 1 (Th1) cell-mediated inflammatory disorders, mainly based on the abundance of activated Th1 cells in the inflamed synovium and the pathogenetic role of proinflammatory cytokines that are mainly produced by Th1 cell-stimulated monocytes. In contrast, the pathogenesis of systemic onset disease differs from that of other types of JRA in several respects, including the lack of association with human leukocyte antigen type and the absence of autoantibodies or autoreactive T cells. Although the precise mechanism that leads to JRA remains unclear, proinflammatory cytokines are thought to be responsible for at least part of the clinical symptoms in all JRA types. The effectiveness of biologic therapy in blocking the action of these cytokines in JRA patients provides strong evidence that they play a fundamental role in JRA inflammation.

HLA B27 allele types in homogeneous groups of juvenile idiopathic arthritis patients in Latvia

Juvenile idiopathic arthritis (JIA) is a heterogeneous condition and therapeutic strategies vary in different JIA types. The routinely accepted practice to start with Sulphasalazine (SS) as the first line treatment in patients with HLA B27 positive JIA proves to be ineffective in a large proportion of children.

OBJECTIVE

to investigate HLA B27 positive JIA patients clinical characteristics, determined HLA B27 allele types and their connection with antirheumatic treatment in homogenous patient groups.

MATERIALS AND METHODS

56 patients diagnosed with JIA and observed over the period 2006 to 2009 included in the study. HLAB27 allele types were determined using PCR method.

RESULTS

In HLA B27 positive JIA patients mean disease onset was 12.34 ± 3.3 years. Most common (44%) JIA type was enthesitis related arthritis. Positive response to the treatment with SS was found in 32% of patients, Methotrexate (MTX) - in 43%, combined treatment - SS with MTX was effective in 12.5%. 12.5% of patients required combination MTX with Enbrel.Eight HLA B27 allele types were found in JIA patients in Latvia: *2702, *2703, *2704, *2705, *2710, *2715, *2717, *2728. The most common was *2705 - in 55% of cases. Among all the patients enthesitis related arthritis most commonly occurred in patients with HLAB*2705 allele (OR = 2.01, p < 0.02), oligoarthritis in patients with *2710 allele (OR = 3.0, p < 0.04) and polyarthritis with *2717 allele (OR = 3.0, p < 0.05). In patients with *2705 allele effective treatment was MTX (OR = 1.13, p < 0.03) and MTX with SS (OR = 2.02, p < 0.05), but in patients having *2703 allele - MTX with Enbrel (OR = 2.94, p < 0.02).

CONCLUSIONS

There are 8 different HLA B27 alleles in JIA patients in Latvia and the most common is *2705, but in order to assert them to be disease associated alleles, more extensive studies are needed, including control group of HLA B27 positive healthy individuals. Standard treatment approach with SS proves to be unsatisfactory in the majority of JIA patients. To improve children's quality of life achieving rapid disease control, the first line treatment in HLA B27 positive patients should be MTX. In order to start with the most appropriate drug it is necessary to determine HLAB 27 type at the onset of disease.

Identification of a novel candidate locus for juvenile idiopathic arthritis at 14q13.2 in the Latvian population by association analysis with microsatellite markers

To identify novel juvenile idiopathic arthritis (JIA) susceptibility loci, a 270 kb genomic region encompassing FAM177A1, KIAA0391, and PSMA6 genes was genotyped in 97 oligoarthritis (JIoA) and 50 polyarthritis (JIpA) patients and 230 individuals without autoimmune disorders by five microsatellites (MS) previously described as HSMS markers of the 14q13.2 region. Direct sequencing revealed two variable components of the (CAA)(n)(A)(m) motif in HSMS602 marker (FAM177A1 gene). Repeat (AC)(5)AT(AC)(n) of the HSMS701 (KIAA0391 gene) was variable in the Latvian population only in its downstream part. Allele (AC)(5)AT(AC)(15) of HSMS701 was found to be strongly associated with JIA (p = 4.91 x 10(-5), odds ratio [OR] = 18.87) and modestly associated with JIpA (p = 1.64 x 10(-3), OR = 15.69). Alleles (AC)(5)AT(AC)(18) of HSMS701 and (TG)(10) of HSMS702 appear to be JIA and JIoA risk factors (p = 1.09 x 10(-3), OR = 2.64 and p = 2.00 x 10(-3), OR = 7.67, respectively), but allele 168 bp of HSMS602 (p = 9.02 x 10(-4), OR = 0.35) appears to be protective. Two heterozygote genotypes (TG)(20/23) of the HSMS006 and (AC)(22/23) of the HSMS801 showed association with JIA (p < 2 x 10(-3)), but homozygote (TG)(19/19) was found to be protective (p = 5.41 x 10(-4), OR = 0.12). Our results define an additional susceptibility locus for JIA at the 14q13.2 genomic region encompassing KIAA0391 and PSMA6 genes.

Preferential immunoglobulin oxidation in children with juvenile idiopathic arthritis

OBJECTIVE

Juvenile idiopathic arthritis (JIA) is a rare chronic inflammatory disorder of the joints. There is strong evidence that oxidative damage occurs in rheumatoid diseases, including JIA. The increased level of protein oxidation products in total plasma proteins has recently been reported in children with diagnosed JIA. The objective of this study was to find out which fraction of plasma proteins is mostly damaged by oxidative stress and whether the damaging effect correlates with certain clinical or laboratory parameters.

METHODS

A new approach to estimate the carbonyl content of plasma protein fractions was developed, based on two-stage electrophoresis and immunochemical detection of the carbonyl derivatives of the proteins. This method allowed us to detect and quantitate carbonyl groups in the albumin, alpha-2, beta and gamma-globulin fractions. Sera of 25 children with JIA and 13 healthy controls were tested.

RESULTS

Albumin and gamma-globulins were found to be most modified by oxidation. In a group of children with systemic JIA, both albumin and gamma-globulins were oxidized while plasma gamma-globulin fraction damage was prevalent in pauciarticular JIA.

CONCLUSIONS

Among plasma proteins of children with JIA, gamma-globulins were preferentially oxidized, whereas most of the other proteins did not seem to be affected. Oxidative modification of plasma proteins was correlated with the type of JIA. These findings may allow the use of carbonyls as clinical markers of inflammatory process activity in patients with different types of JIA. It is also a potential tool for monitoring oxidative protein damage in other diseases and therapies.

Ankle Disease in Juvenile Idiopathic Arthritis: Ultrasound Findings in Clinically Swollen Ankles

Objective.

The ankle joint is frequently involved in juvenile idiopathic arthritis (JIA), but it is unclear whether this is predominantly due to synovitis, tenosynovitis, or both. We performed clinic-based ultrasound examination to assess the prevalence of synovitis and tenosynovitis in children with JIA felt clinically to have active inflammatory disease of the ankle.

Methods.

Thirty-four patients with 49 clinically swollen ankles were studied (19 polyarticular JIA, 13 oligoarticular JIA, 1 systemic JIA, 1 psoriatic JIA). All cases had at least one clinically swollen ankle joint. The children were assessed clinically and had ultrasound examination during routine clinic appointments.

Results.

We found 71% of ankles had tenosynovitis and 39% had tenosynovitis alone. Only 29% of swollen ankles had a tibiotalar effusion alone. We found 33% had both tenosynovitis and a tibiotalar effusion. When results were analyzed by JIA subtype, we found 81% of oligoarticular JIA ankles had medial ankle tenosynovitis but only 19% had tibiotalar effusion alone. There was a significant difference between JIA subgroups for the frequency of occurrence of medial ankle tenosynovitis (p = 0.048) and lateral ankle tenosynovitis (p = 0.001).

Conclusion.

The tibiotalar joint was not involved in 39% of the swollen ankles; and tenosynovitis, sometimes in isolation, was the dominant finding. This has implications for therapeutic intervention and also for an improved classification of children with JIA, especially with ankle involvement.

Laboratory tests in the diagnosis and follow-up of pediatric rheumatic diseases: an update

OBJECTIVES

We reviewed the literature to evaluate the role of common laboratory tests and to examine the recent progress in the laboratory diagnosis of pediatric rheumatic diseases.

METHODS

We used the PubMed database (1950-2008) to search for the keywords "laboratory," "erythrocyte sedimentation rate" (ESR), "C-reactive protein" (CRP), "blood cytology," "procalcitonin" (PCT), "complement system," "ferritin," "antistreptolysin O titer" (ASO), "autoantibodies," "genetic studies," in conjunction with "rheumatic disease in children" and "pediatric autoimmune diseases." All relevant original and review articles in English were reviewed as well as textbooks of pediatric rheumatology.

RESULTS

Laboratory tests (ESR, CRP, blood cytology, complement system, ferritin, ASO titer) play an important role in confirming a diagnosis and in the follow-up of rheumatic diseases in the pediatric age group. The ESR is probably the most widely measured index of the acute phase response. Measurement of CRP is very useful in the rapid diagnosis of infection as a progressive increase can be shown in the first 48 hours. Also, the subsequent fall in serum CRP concentration on resolution of inflammation is useful for monitoring the efficacy of treatment. In chronic diseases, a combination of CRP and ESR may provide the most useful information. Cytopenia and different forms of anemia can be encountered in many rheumatic diseases: they can be related to disease activity or to therapeutic side effects. Determination of complement levels (C3 and/or C4) is useful in the follow-up of systemic lupus erythematosus (SLE) and membranoproliferative glomerulonephritis. Ferritin is a laboratory hallmark of primary and secondary hemophagocytic lymphohistiocytosis. ASO titer should be obtained to confirm a diagnosis of acute rheumatic fever; other important antibody markers of streptococcal infection include antihyaluronidase, antideoxyribonuclease B, and antistreptokinase antibodies. We also found that, in the pediatric age, the main indication for synovial fluid analysis is suspected joint infection. Antinuclear antibodies, anti-Smith antigen, and anti-double-stranded DNA antibodies are important in the diagnosis of SLE, are useful prognostic markers, and facilitate clinical and treatment follow-up. Anti-SSA/Ro and anti-SSB/La antibodies are associated with Sjögren's syndrome and congenital heart block, while the anti-U1 small nuclear ribonucleoprotein antibodies show high specificity for mixed connective tissue disease. Repetitive spontaneous abortions, thrombocytopenia, and many types of venous or arterial thrombosis are associated with antiphospholipid antibodies. The presence of cytoplasmic antineutrophil antibodies is essential in the diagnosis of Wegener granulomatosis. The discovery of underlying single causative gene defects led to the identification of several autoinflammatory diseases, a group of genetic disorders characterized by recurrent attacks of inflammation (hereditary periodic fever syndromes). These include familial Mediterranean fever due to mutations in the Mediterranean fever (MEFV) gene, hyperimmunoglobulinemia D syndrome due to mutations in the MK gene for mevalonate kinase, cryopyrinopathies such as Muckle-Wells syndrome or neonatal-onset multisystemic inflammatory disease (neonatal-onset multisystemic inflammatory disease or chronic infantile neurological cutaneous and articular (CINCA)) associated with cold-induced autoinflammatory syndrome 1 gene mutations, and tumor necrosis factor receptor-associated periodic syndrome due to mutation of TNF receptor I gene.

CONCLUSIONS

Laboratory investigations play an important role in the diagnosis and follow-up of inflammatory rheumatic diseases in children. A good history and a complete physical examination are the best screening tests. Routine laboratory tests are useful to confirm a suspected diagnosis, to assess disease activity, and to measure the response and toxicity to treatment. Only a few tests represent diagnostic criteria such as antinuclear antibodies and anti-double-stranded DNA in SLE or cytoplasmic antineutrophil cytoplasmic autoantibodies in Wegener's granulomatosis. Recent advances in molecular genetics have impacted diagnosis, pathogenesis, and treatment in genetic fever syndromes.

Identification of a novel susceptibility locus for juvenile idiopathic arthritis by genome-wide association analysis

OBJECTIVE

Juvenile idiopathic arthritis (JIA) is a chronic rheumatic disease of childhood. Two well-established genetic factors known to contribute to JIA susceptibility, HLA and PTPN22, account for less than half of the genetic susceptibility to disease; therefore, additional genetic factors have yet to be identified. The purpose of this study was to perform a systematic search of the genome to identify novel susceptibility loci for JIA.

METHODS

A genome-wide association study using Affymetrix GeneChip 100K arrays was performed in a discovery cohort (279 cases and 184 controls). Single-nucleotide polymorphisms (SNPs) showing the most significant differences between cases and controls were then genotyped in a validation sample of cases (n = 321) and controls, combined with control data from the 1958 UK birth cohort (n = 2,024). In one region in which association was confirmed, fine-mapping was performed (654 cases and 1,847 controls).

RESULTS

Of the 112 SNPs that were significantly associated with JIA in the discovery cohort, 6 SNPs were associated with JIA in the independent validation cohort. The most strongly associated SNP mapped to the HLA region, while the second strongest association was with a SNP within the VTCN1 gene. Fine-mapping of that gene was performed, and 10 SNPs were found to be associated with JIA.

CONCLUSION

This study is the first to successfully apply a SNP-based genome-wide association approach to the investigation of JIA. The replicated association with markers in the VTCN1 gene defined an additional susceptibility locus for JIA and implicates a novel pathway in the pathogenesis of this chronic disease of childhood.

A comprehensive review of the genetics of juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common chronic arthropathy of childhood which is believed to be influenced by both genetic and environmental factors. The progress in identifying genes underlying JIA susceptibility using candidate gene association studies has been slow. Several associations between JIA and variants in the genes encoding the human leukocyte antigens (HLA) have been confirmed and replicated in independent cohorts. However it is clear that genetic variants outside the HLA also influence susceptibility to JIA. While a large number of non-HLA candidate genes have been tested for associations, only a handful of reported associations such as PTPN22 have been validated. In this review we discuss the principles behind genetic studies of complex traits like JIA, and comprehensively catalogue non-HLA candidate-gene association studies performed in JIA to date and review several validated associations. Most candidate gene studies are underpowered and do not detect associations, and those that do are often not replicated. We also discuss the principles behind genome-wide association studies and discuss possible implications for identifying genes underlying JIA. Finally we discuss several genetic variants underlying multiple clinically distinct autoimmune phenotypes.

Juvenile idiopathic arthritis

Juvenile idiopathic arthritis is a broad term that describes a clinically heterogeneous group of arthritides of unknown cause, which begin before 16 years of age. This term encompasses several disease categories, each of which has distinct methods of presentation, clinical signs, and symptoms, and, in some cases, genetic background. The cause of disease is still poorly understood but seems to be related to both genetic and environmental factors, which result in the heterogeneity of the illness. Although none of the available drugs has a curative potential, prognosis has greatly improved as a result of substantial progresses in disease management. The most important new development has been the introduction of drugs such as anticytokine agents, which constitute a valuable treatment option for patients who are resistant to conventional antirheumatic agents. Further insights into the disease pathogenesis and treatment will be provided by the continuous advances in understanding of the mechanisms connected to the immune response and inflammatory process, and by the development of new drugs that are able to inhibit selectively single molecules or pathways.

Novel self-epitopes derived from aggrecan, fibrillin, and matrix metalloproteinase-3 drive distinct autoreactive T-cell responses in juvenile idiopathic arthritis and in health

Juvenile idiopathic arthritis (JIA) is a heterogeneous autoimmune disease characterized by chronic joint inflammation. Knowing which antigens drive the autoreactive T-cell response in JIA is crucial for the understanding of disease pathogenesis and additionally may provide targets for antigen-specific immune therapy. In this study, we tested 9 self-peptides derived from joint-related autoantigens for T-cell recognition (T-cell proliferative responses and cytokine production) in 36 JIA patients and 15 healthy controls. Positive T-cell proliferative responses (stimulation index ≥2) to one or more peptides were detected in peripheral blood mononuclear cells (PBMC) of 69% of JIA patients irrespective of major histocompatibility complex (MHC) genotype. The peptides derived from aggrecan, fibrillin, and matrix metalloproteinase (MMP)-3 yielded the highest frequency of T-cell proliferative responses in JIA patients. In both the oligoarticular and polyarticular subtypes of JIA, the aggrecan peptide induced T-cell proliferative responses that were inversely related with disease duration. The fibrillin peptide, to our knowledge, is the first identified autoantigen that is primarily recognized in polyarticular JIA patients. Finally, the epitope derived from MMP-3 elicited immune responses in both subtypes of JIA and in healthy controls. Cytokine production in short-term peptide-specific T-cell lines revealed production of interferon-γ (aggrecan/MMP-3) and interleukin (IL)-17 (aggrecan) and inhibition of IL-10 production (aggrecan). Here, we have identified a triplet of self-epitopes, each with distinct patterns of T-cell recognition in JIA patients. Additional experiments need to be performed to explore their qualities and role in disease pathogenesis in further detail.

Juvenile idiopathic arthritis: the paediatric perspective

Paediatric rheumatology is a relatively new specialty that has developed rapidly over the last 30 years. There have been major advances, which have included improvements in the classification and management of juvenile idiopathic arthritis (JIA). The former has led to enhanced international collaboration with disease registries, multicentre research and the development of new therapeutic agents. This has resulted in improved disease control and remission induction in many. There is, however, still significant morbidity associated with JIA during childhood, adolescence and adulthood, and challenges for the future include early identification of those with a poorer prognosis, appropriate administration of safe therapies and optimizing outcomes as young people move through adolescence into adulthood.

Outcome following onset of juvenile idiopathic inflammatory arthritis: II. Predictors of outcome in juvenile arthritis

OBJECTIVE

To assess the relative contributions of demographic, clinical and laboratory variables in predicting outcome in juvenile idiopathic inflammatory arthritis (JIA), based on a review of the existing literature.

METHODS

Electronic reference database searches for the previous 10 yr were conducted and studies examining the role of major potential predictors of main outcomes were identified. Where possible, subjects were grouped by JIA disease subtype. In addition to demographic variables, the following disease-related predictors were assessed: nature of joint involvement, acute-phase response, and presence of autoantibodies. These were then analysed for three main outcomes of interest: remission as assessed by disease activity; functional impairment; and structural damage as assessed by radiological joint erosions.

RESULTS

In general, female gender, polyarticular and symmetrical joint involvement, elevated inflammatory markers and rheumatoid factor positivity were the most consistent predictors of a poor outcome, although the studies were frequently inconsistent in both the direction and the magnitude of the effects.

CONCLUSIONS

These data are too variable to accurately identify those predictors associated with poor outcome following the onset of JIA. Although some of this variation may be the result of true differences between study populations, the vast majority of inconsistencies are explainable by the absence of standardized classification systems, outcome definitions, therapeutic approach and research tools. More comprehensive prospective evaluation is required before robust prediction models can be generated.

A functional promoter haplotype of macrophage migration inhibitory factor is linked and associated with juvenile idiopathic arthritis

OBJECTIVE

To establish linkage and replicate the association of macrophage migration inhibitory factor (MIF) with juvenile idiopathic arthritis (JIA).

METHODS

Three hundred twenty-one Caucasian simplex families from the UK were genotyped for polymorphisms of MIF using SNaPshot ddNTP primer extension, or by a fluorescently labeled primer method, and capillary gel electrophoresis. The functional significance of the promoter polymorphisms was studied using luciferase-based reporter gene assays in human T lymphoblast and epithelial cell lines.

RESULTS

MIF was linked and associated with JIA (P = 0.0016). Specifically, a 2-point promoter haplotype, CATT(7)-MIF-173*C, was found to be transmitted in excess (38 transmitted: 21 not transmitted) in the JIA patients. Conditional extended transmission disequilibrium test and pairwise extended transmission disequilibrium test predicted functional interaction between the 2 polymorphic positions. The interaction of the CATT repeat with MIF-173*G/C was found to be specific to the cell type.

CONCLUSION

Replication of an association and linkage of MIF with JIA has been established. Functional interaction between the polymorphic positions on the linked haplotype has also been shown. The molecular mechanism of this interaction is currently being investigated.

Advances in paediatric rheumatology: beyond NSAIDs and joint replacement

Over the previous three decades there have been a number of dramatic changes in our understanding of both the pathogenesis and epidemiology of the rheumatic diseases of childhood. Improvements in the classification of paediatric-onset arthritides and international collaboration in terms of multicentre research have led to the development of new therapeutic agents and better methods of outcome assessment for these chronic and often disabling conditions. Fortunately for children with paediatric rheumatic diseases treatment regimes are now available that provide excellent disease control for many and remission induction for some. Challenges include clearer definition of the genetics and pathogenesis of the diseases, delineation of reliable biological markers for diagnosis and monitoring of disease activity. The future should also herald early identification of those with a poorer prognosis, together with the design of more powerful, safer and cheaper remission-inducing agents, given to the right patients at the right time.

Epidemiology of the rheumatic diseases of childhood

Epidemiologic studies of pediatric rheumatologic disease are becoming increasingly focused on subfields of epidemiology. Genetic epidemiology is assuming an ever-greater role in the understanding of disease risks and pathogenesis. Such studies involve major histocompatibility complex, cytokine gene polymorphisms, T cell studies, and microarray-based expression technology. Clinical epidemiology, the study of occurrence and outcomes, increasingly relies on multicenter studies with data improving as study parameters become more standardized. With multicenter studies, there is an increasing trend to study ethnic differences in rheumatologic diseases of children.