Classification of childhood arthritis: a work in progress

Juvenile Idiopathic Arthritis and COVID-19 Pandemic: Good Compliance With Treatment, Reluctance to Return to School

Objective: The SARS-CoV-2 pandemic has induced an exceptional sanitary crisis, potentially having an impact on treatment continuation, for juvenile idiopathic arthritis (JIA) patients receiving immunosuppressive therapies. After national lockdowns, many patients were also concerned about their safety at school. We evaluated the impact of the pandemic on the optimal continuation of treatment and on the return to school in JIA patients.

Methods: JIA patients under 18 years of age, usually treated with disease-modifying anti-rheumatic drugs (DMARDs) were prospectively included during their outpatient visit and completed a standardized questionnaire. The primary outcome was DMARD treatment modification in relation to the context of the pandemic but we also evaluated the pandemic's impact on the schooling.

Results: One hundred and seventy three patients from 8 different expert centers were included between May and August 2020. Their mean age was 11.6 years (± 4.1 years), and most of them 31.2% (54/173) had a rheumatoid factor-negative polyarticular JIA. Fifty percent (86/172) were treated with methotrexate, and 72.5% (124/171) were treated with bDMARDs. DMARD treatment modification in relation to the pandemic was observed in 4.0% (7/173) of participants. 49.1% (81/165) of the patients did not return to school due to a personal/parental decision in 69.9% (55/81) of cases. Two patients were diagnosed positive for SARS-CoV-2 infection.

Conclusion: This study suggests that JIA patients treated with DMARDs continued their treatment during the pandemic and were rarely affected by symptomatic COVID-19. In contrast, parents' reluctance was a major obstacle for returning to school. Therefore, more solidified school reopening strategies should be developed.

Empowering Young People Living With Juvenile Idiopathic Arthritis to Better Communicate With Families and Care Teams: Content Analysis of Semistructured Interviews

Background

Young people living with juvenile idiopathic arthritis (JIA) face a number of communication barriers for achieving optimal health as they transition from pediatric care into adult care. Despite growing interest in mobile or wireless technologies to support health (mHealth), it is uncertain how these engagement tools might support young people, their families, and care teams to optimize preference-based treatment strategies.

Objective

This study aims to examine how an mHealth patient support system (mPSS) might foster partnership between young people living with JIA, their families, and care teams.

Methods

Semistructured interviews with young people (5-15 years old), their families, and JIA care teams were conducted using researcher-developed interviews guides. Transcribed data were qualitatively analyzed using conventional content analysis.

Results

We conducted semistructured interviews with 15 young people, their parents, and 4 care team members. Content analysis revealed the potential of an mPSS to support productive dialogue between families and care teams. We identified four main themes: (1) young people with JIA face communication challenges, (2) normalizing illness through shared experience may improve adherence, (3) partnership opens windows into illness experiences, and (4) readiness to engage appears critical for clinic implementation.

Conclusions

A human-centered mPSS design that offers JIA patients the ability to track personally relevant illness concerns and needs can enhance communication, generate consensus-based treatment decisions, and improve efficiency and personalization of care. Technology that supports continuous learning and promotes better understanding of disease management may reduce practice burden while increasing patient engagement and autonomy in fostering lasting treatment decisions and ultimately supporting personalized care and improving outcomes.

Comorbidity of Type 1 Diabetes Mellitus in Patients with Juvenile Idiopathic Arthritis

OBJECTIVES

To determine the prevalence of type 1 diabetes mellitus (T1D) in patients with juvenile idiopathic arthritis (JIA) and to characterize patients having both.

STUDY DESIGN

Diabetes comorbidity was recorded in the National Pediatric Rheumatologic Database since 2012. Data from the North Rhine-Westphalian diabetes registry served as the reference population for the prevalence of diabetes in the general population. The National Pediatric Rheumatologic Database data were indirectly standardized for age and sex for comparison with the general population. The diabetes prevalence ratio was calculated using the Poisson regression model.

RESULTS

The analysis included 12 269 patients with JIA. A total of 58 patients had comorbid T1D, and the diabetes prevalence was 0.5%. The mean age was 11.6 years at the time of documentation, and the mean disease duration was 4.2 years. Compared with the general population, the prevalence of diabetes in patients with JIA was significantly increased (prevalence ratio 1.76 [95% CI 1.34; 2.28], P < .001). The onset of diabetes in patients with JIA was earlier than that reported in the reference data. Sixty-three percent of patients developed T1D before JIA. On average, diabetes onset was 56 months before the onset of JIA. Patients who first developed JIA developed T1D on average 40 months later. The majority of patients had not received disease-modifying antirheumatic drugs before diabetes onset.

CONCLUSIONS

T1D occurs more frequently in patients with JIA than in the general population. The likelihood of T1D occurrence appears to be slightly higher before JIA manifestation and without disease-modifying antirheumatic drug therapy after JIA onset.

Education and employment in patients with juvenile idiopathic arthritis - a standardized comparison to the German general population

BACKGROUND

Although several studies show that JIA-patients have significantly lower employment rates than the general population, the research on educational and occupational attainments in patients with juvenile idiopathic arthritis (JIA) remain conflicting most likely due to small sample sizes. Therefore, aim of this study is to compare the educational achievements and employment status of 3698 JIA-patients with the German general population (GGP).

METHODS

"SEPIA" was a large cross-sectional study on the current status of a historic cohort of JIA-patients treated in a single center between 1952 and 2010. For the analyses of education and employment a sub-cohort was extracted, including only adult cases with a confirmed diagnosis of JIA (N = 2696). Participants were asked to fill out a standardized written questionnaire on education and employment. Outcome measures (education/unemployment) were directly standardized to the GGP using data obtained from the National Educational Panel Study 2013 (N = 11,728) and the German Unemployment Statistics 2012 of the Federal Statistical Office (N = 42,791,000).

RESULTS

After age- and sex-standardization, 3% (95% Confidence Interval 1.9 to 4.1%) more of the JIA-patients (26%) than of the GGP (23%) had only reached primary education. In contrast, parents of JIA-patients had similar levels of education as parents in the GGP. With a standardized difference of 0.2% (95% CI: 0.16 to 0.19%), the unemployment rate in JIA-patients was slightly, but not significantly higher than in the GGP. Stratifying for disease duration and the current treatment status, differences were confirmed for persons diagnosed before 2001, whilst for patients diagnosed after 2000, differences were found only in JIA-patients with ongoing disease. Medium and high educational achievements did not differ statistically significant between JIA patients and the GPP.

CONCLUSION

Educational achievements in German JIA-patients are significantly lower than in the GGP. Furthermore we were able to identify a slightly higher level of unemployment, especially in those with still under treatment and longer disease duration. Better treatment options as well as further development of social support programs might help to overcome this lifelong secondary effect of JIA.

Views from the Inside, Part 1: Routes to Diagnosis — Families' Experience of Living with a Child with Arthritis

This is the first of a trilogy of articles that presents the experiences and perspectives of 46 families about what it is like to live with and care for a child with juvenile idiopathic arthritis (JIA).

An independent professional recruited the children from a random sample of families who attended consecutive outpatient appointments at the juvenile arthritis clinic and who fulfilled the inclusion criteria. Qualitative and quantitative data from self-completion questionnaires, transcripts from semi-structured interviews with family members in their homes, family-filmed video diaries, and diaries written by siblings and children with arthritis were analysed. These different types of data were gathered over 18 months in order to collect information about the fluctuating nature of this disease and the impact of this changeability on family members.

Part 1 concentrates on a brief presentation of relevant literature, presents a simplified map of the findings and introduces the families' early experiences of seeking and coping with the diagnosis of JIA. The article explores the myth that arthritis only affects elderly and infirm people, explains the mirage effect and discusses the significance of different routes to diagnosis. The majority of the families felt that these early events had a significant, sometimes considerable, impact upon how they coped later, including how they related subsequently to health care professionals and engaged with continuing prescribed health care programmes.

The findings report the families' experiences as recipients of health care by many different professionals and relate to their recollection and interpretation of events. Research into the professionals' perspectives would be illuminating but did not fall within the scope of the present study. The experiences of families of children with arthritis are shared by families of children with other chronic conditions and by other carers and service users.

Using the Effects of Youngsters' Eyesight on Quality of Life Questionnaire to Measure Visual Outcomes in Children With Uveitis

OBJECTIVE

The Effects of Youngsters' Eyesight on Quality of Life (EYE-Q) is a novel measure of vision-related quality of life (QOL) and function in children. We aim to determine the validity of the EYE-Q in childhood uveitis.

METHODS

We abstracted medical record data on arthritis and uveitis in a convenience sample of children with juvenile idiopathic arthritis (JIA) and/or uveitis. In addition to the EYE-Q, parents and patients completed questionnaires on overall QOL (Pediatric Quality of Life Inventory [PedsQL]), and physical functioning (Childhood Health Assessment Questionnaire [C-HAQ]).

RESULTS

Among 57 children (8 JIA, 24 JIA and uveitis, 25 uveitis alone), 102 ocular examinations were performed within 1 month of completing questionnaires. Uveitis patients had bilateral disease (69%), anterior involvement (78%), synechiae (51%), and cataracts (49%). Children with vision loss in their better eye (visual acuity [VA] 20/50 or worse) had worse EYE-Q (P = 0.006) and PedsQL (P = 0.028) scores, but not C-HAQ scores. The EYE-Q moderately correlated with logMAR VA (rs  = -0.43), PedsQL (rs  = 0.43), and C-HAQ (rs  = -0.45), but was not correlated with anterior chamber cells or intraocular pressure. The PedsQL and C-HAQ did not correlate with VA or cells. There were strong correlations between the parent and child EYE-Q (rs  = 0.62). Cronbach's α for the child report was 0.91. The EYE-Q had strong test-retest reliability (rs  = 0.75).

CONCLUSION

The EYE-Q may be an important tool in the assessment of visual outcomes in childhood uveitis and an improvement over general measures in detecting changes in vision-related function.

Antinuclear antibody-positive cohort constitutes homogeneous entity in juvenile idiopathic arthritis

OBJECTIVE

To identify a homogeneous entity for antinuclear antibody (ANA)-positive patients suffering from juvenile idiopathic arthritis (JIA).

METHODS

All of the clinical features were recorded retrospectively. ANA positivity was defined as more than twice positive results at a titer of > 1:100. The correlation between ANA positivity and clinical parameters was assessed by multiple logistic regression analysis.

RESULT

Of 120 patients, 49 patients were ANA positive (31 oligoarthritis, 18 rheumatoid factor [RF]-negative polyarthritis) and 71 patients were ANA negative (48 oligoarthritis, 23 RF-negative polyarthritis), and were recruited retrospectively to this study according to the International League of Associations for Rheumatology (ILAR) criteria. In ANA-positive cohort, the characteristics of early-onset age, female predominance, and asymmetric arthritis were observed compared with ANA-negative cohort including oligoarthritis and RF-negative polyarthritis. Correspondingly, we found that ANA-positive cohort had higher cumulative number of joints affected at 9 and 12 months after disease presentation than ANA-negative cohort, had lower frequency of occurrence of image change, and had a different pattern of affected arthritis than ANA-negative cohort, which was more likely to have knee involvement and less likely to have hip and shoulder involvement. ANA positivity correlated strongly with asymmetric arthritis, female predominance and wrist involvement.

CONCLUSION

This study demonstrates that ANA-positive cohort divided into different subgroups by present ILAR criteria share the similar features and suggests that ANA positivity might serve as a novel potential value for JIA classification.

Total pubertal growth in patients with juvenile idiopathic arthritis treated with growth hormone: analysis of a single center

OBJECTIVES

Growth failure is a permanent sequelae in juvenile idiopathic arthritis (JIA). The aim of the study was to compare pubertal growth in control and growth hormone (GH) treated JIA subjects.

DESIGN

64 children with JIA at a mean age of 10.38 ± 2.80 years were enrolled and followed until final height (measured in standard deviation (SD) scores). 39 children (20 m) received GH therapy and 24 (9 m) served as controls. GH dose was 0.33 mg/kg/week. Linear regression analysis was performed to identify factors influencing total pubertal growth.

RESULTS

Mean total pubertal growth was 21.1 ± 1.3 cm (mean ± SD) in GH treated JIA patients and 13.8 ± 1.5 cm in controls. Final height was significantly higher with GH treatment (-1.67 ± 1.20 SD) compared to controls (-3.20 ± 1.84 SD). Linear regression model identified age at onset of puberty (ß=-4.2,CI: -5.9, -2.6 in controls and ß=-2.3,CI: -3.6, -1.1 in GH treated) as the main factor for total pubertal growth. Final height SDS was determined by the difference to target height at onset of puberty (ß=-0.59;CI: -0.80, -0.37 in controls and ß=-0.30,CI: -0.52, -0.08 in GH treated), age at onset of puberty (ß=0.47;CI:0.02,0.93 in controls and 0.23;CI: -0.00,0.46 in GH treated) and height gain during puberty (ß=0.13;CI:0.05,0.21 in controls and ß=0.11;CI:0.07,0.16 in GH treated).

CONCLUSION

Total pubertal growth in JIA patients treated with GH was increased by a factor of 1.5 greater in comparison to controls leading to a significantly better final height. To maximize final height GH treatment should be initiated early to reduce the height deficit at onset of puberty.

Growth retardation and delayed puberty in children and adolescents with juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common joint disorder in developing children. Juvenile idiopathic arthritis is difficult to diagnose and treat. In some patients, signs and symptoms can be frustratingly inconsistent, contradictory or idiosyncratic. Short stature in patients with JIA is usually due to reduced growth in the lower extremities, and only rarely due to reduced growth in the spinal column. In some studies, children with JIA were found to have infantile body proportions. Puberty is delayed in children with JIA. In children with chronic arthritic disorders, there is a strong correlation between the activity of the disease and the age of puberty. The main goals in reducing growth retardation in children with JIA are promoting timely remission and reducing the duration and dosage of corticosteroid treatment. It is important to regularly monitor physical development. Further improvements to the treatment protocol depend on continued interdisciplinary research involving paediatricians, rheumatologists and clinical anthropologists.

Oligoarticular and polyarticular JIA: epidemiology and pathogenesis

Juvenile idiopathic arthritis (JIA) refers to a group of chronic childhood arthropathies of unknown etiology, currently classified into subtypes primarily on the basis of clinical features. Research has focused on the hypothesis that these subtypes arise through distinct etiologic pathways. In this Review, we discuss four subtypes of JIA: persistent oligoarticular, extended oligoarticular, rheumatoid-factor-positive polyarticular and rheumatoid-factor-negative polyarticular. These subtypes differ in prevalence between ethnic groups and are associated with different HLA alleles. Non-HLA genetic risk factors have also been identified, some of which reveal further molecular differences between these subtypes, while others suggest mechanistic overlap. Investigations of immunophenotypes also provide insights into subtype differences: adaptive immunity seems to have a prominent role in both polyarticular and oligoarticular JIA, and the more-limited arthritis observed in persistent oligoarticular JIA as compared with extended oligoarticular JIA may reflect more-potent immunoregulatory T-cell activity in the former. Tumor necrosis factor seems to be a key mediator of both polyarticular and oligoarticular JIA, especially in the extended oligoarticular subtype, although elevated levels of other cytokines are also observed. Limited data on monocytes, dendritic cells, B cells, natural killer T cells and neutrophils suggest that the contributions of these cells differ across subtypes of JIA. Within each subtype, however, common pathways seem to drive joint damage.

Comparison of patients with juvenile psoriatic arthritis and nonpsoriatic juvenile idiopathic arthritis: how different are they?

OBJECTIVE

To compare the clinical features and outcome between patients with juvenile psoriatic arthritis (JPsA) and non-JPsA juvenile idiopathic arthritis (JIA).

METHODS

Fifty-three children with JPsA, 32 with < 5 joints in the first 6 months of disease (oligo-JPsA) and 21 (> or = 5 joints) polyarticular-onset (poly-JPsA) were compared to 53 patients with JIA who were matched by sex, age, date of diagnosis, and articular onset pattern.

RESULTS

There was no difference in the percentage of patients between the oligoarticular groups who developed extended oligoarthritis or in the percentage of patients who were positive for antinuclear antibodies. The only differences were that 25% of patients with oligo-JPsA had dactylitis compared to 0% of patients with oligo-JIA (p < 0.01) and 50% had nail pitting as compared to 18.7% (p < 0.05). In polyarticular patients the percentages with dactylitis were similar (19% vs 38%; p = 0.25). The frequency of uveitis was identical in the oligoarticular patients but a higher rate was seen in poly-JPsA compared to poly-JIA (23.8% vs 0%; p = 0.02), while contractures were more frequent in poly-JIA compared to poly-JPsA during the course of the illness (47.6% vs 14.3%; p = 0.03) but not at last followup (14.3% vs 4.7%; p = 0.6). At last followup the mean Childhood Health Assessment Questionnaire scores were similar in both the polyarticular and oligoarticular groups.

CONCLUSION

There were only a few differences between patients with JPsA and JIA regarding disease onset, disease course, and outcome. We suggest that large, longterm prospective studies are required to accurately determine whether subdividing JIA according to psoriasis is worthwhile.

Improvement of reduced serum cartilage oligomeric matrix protein levels in systemic juvenile idiopathic arthritis patients treated with the anti-interleukin-6 receptor monoclonal antibody tocilizumab

In this study, we determined serum cartilage oligomeric matrix protein (COMP) levels in systemic juvenile idiopathic arthritis (sJIA) patients during both the active and the remission phases to investigate how the growth cartilage turnover changed under tocilizumab treatment. Specimens were collected from 201 healthy children under 16 years of age with no growth impairment, and paired sera were collected from 11 sJIA patients treated with tocilizumab. Disease activity was assessed from white blood cell count, erythrocyte sedimentation rate, C-reactive protein, and ferritin, and the COMP concentration was determined by sandwich enzyme-linked immunosorbent assay. Serum COMP concentrations were found independent of age, and the mean value in healthy children was 17.74+/-5.6 U/L. The mean serum COMP in sJIA patients during the active phase was 10.75+/-3.9 U/L, lower than that of healthy children. The mean serum COMP in the remission phase (14.89+/-3.9 U/L) was significantly higher than that in the active period (P<0.05). These results suggested that in sJIA patients, a reduced serum COMP concentration is a useful marker of active disease and growth impairment, and that the growth cartilage turnover suppressed during the active phase is improved in the remission phase under tocilizumab treatment.

Positive association ofSLC26A2 gene polymorphisms with susceptibility to systemic-onset juvenile idiopathic arthritis

OBJECTIVE

To investigate SLC26A2, the gene that causes diastrophic dysplasia, in juvenile idiopathic arthritis (JIA).

METHODS

Nine polymorphisms across the SLC26A2 gene locus were investigated using MassArray genotyping in 826 UK Caucasian JIA cases and 617 ethnically matched healthy controls.

RESULTS

Significant associations between multiple single-nucleotide polymorphisms (SNPs) across SLC26A2 and systemic-onset JIA were found. In each case, homozygosity for the minor allele conferred the increased risk of disease susceptibility: rs1541915 (odds ratio [OR] 2.3, 95% confidence interval [95% CI] 1.4-3.7, P=0.0003), rs245056 (OR 2.8, 95% CI 1.7-4.6, P=0.00002), rs245055 (OR 2.5, 95% CI 1.2-5.0, P=0.004), rs245051 (OR 2.3, 95% CI 1.4-3.7, P=0.0005), rs245076 (OR 2.7, 95% CI 1.3-5.4, P=0.0015), and rs8073 (OR 2.3, 95% CI 0.9-5.6, P=0.04).

CONCLUSION

These findings show the value of using monogenic disease loci as candidates for investigation in JIA. We identified a subgroup-specific association between SNPs within the SLC26A2 gene and systemic-onset JIA. Our findings also highlight systemic-onset JIA as being a distinctly different disease from that in the other JIA subgroups.

Wnt-1-inducible signaling pathway protein 3 and susceptibility to juvenile idiopathic arthritis

OBJECTIVE

To determine whether Wnt-1-inducible signaling pathway protein 3 (WISP3) polymorphisms are associated with susceptibility to juvenile idiopathic arthritis (JIA).

METHODS

The exons and the intron/exon boundaries of the WISP3 gene were mutation-screened by denaturing high-performance liquid chromatography in 86 patients with polyarticular-course JIA (>/=5 joints affected) and 15 controls. Seven single-nucleotide polymorphisms (SNPs) were genotyped, using allelic discrimination, in a case-control study. Initially, 159 patients with polyarticular-course JIA and 263 controls were studied, followed by study of a replication cohort of 181 patients with polyarticular-course JIA and 355 controls. Available parents of patients with polyarticular-course JIA were also genotyped. Finally, other JIA subgroups were studied (initial cohort, n = 218; replication cohort, n = 213). Single-point and haplotype analysis was carried out.

RESULTS

Positive association with SNP WISP3*G84A was observed and replicated in 2 cohorts of patients with polyarticular-course JIA. Specifically, homozygosity of the mutant allele (WISP3*84AA) conferred a 2-fold increased risk of disease susceptibility (for the initial cohort, odds ratio [OR] 2.1, 95% confidence interval [95% CI] 1.1-4.2, P = 0.03; for the replication cohort, OR 2.0, 95% CI 1.0-4.3, P = 0.05). Strong linkage disequilibrium was observed between SNPs; however, no haplotypic effect of an order of magnitude greater than the single-point WISP3*G84A association was observed. Using the transmission disequilibrium test, a trend toward overtransmission of the WISP3*84A allele was observed in patients with polyarticular-course JIA. No association of any WISP3 polymorphism was observed in the other JIA subgroups.

CONCLUSION

Association and replication of a polymorphism within the first intron of the WISP3 gene have been shown in patients with polyarticular-course JIA. The functional significance of the WISP3*G84A SNP is being determined.

Positive family history of psoriasis does not affect the clinical expression and course of juvenile idiopathic arthritis patients with oligoarthritis

OBJECTIVE

In the 1997 revision of the International League of Associations for Rheumatology (ILAR) criteria for juvenile idiopathic arthritis (JIA), a family history of psoriasis is an exclusion for the oligoarthritis category. We investigated whether psoriasis in a first or second degree relative influences the clinical expression and course of JIA patients with oligoarthritis.

METHODS

In a cross-sectional study, consecutive oligoarticular-onset JIA patients were investigated. Clinical evaluations included confirmation of a family history of psoriasis and assessment of nail abnormalities, dactylitis, psoriatic rash, variables of JIA activity, and laboratory indicators of inflammation. Retrospective assessments included sex, onset age, disease duration, antinuclear antibodies, HLA-B27, uveitis, ocular complications, second-line therapies, intraarticular corticosteroid injections, radiographic joint lesions, joint involvement over time, and laboratory investigations at disease presentation and first observation.

RESULTS

A total of 185 patients were included. Thirty-three had a positive family history of psoriasis (group 2) and 139 did not (group 1). Thirteen patients fulfilled the ILAR criteria for juvenile psoriatic arthritis (group 3). Patients in groups 1 and 2 were comparable for all parameters, except for a higher frequency of females in group 1 (P = 0.04). As compared with group 2, patients in group 3 were less frequently antinuclear antibody positive and had a more severe arthritis and a different distribution of joint involvement.

CONCLUSION

We found close similarities in the clinical features and course among patients with oligoarthritis who had a positive family history for psoriasis and those who did not. These findings argue against the exclusion of the former patients from the oligoarthritis category of JIA.

Heat shock proteins in juvenile idiopathic arthritis: keys for understanding remitting arthritis and candidate antigens for immune therapy

Juvenile idiopathic arthritis (JIA) is in a majority of the cases of self-limiting, and sometimes even a self-remitting, disease. A growing amount of data suggests that active T cell regulation determines, at least partly, the clinical outcome of JIA. In experimental models of arthritis, a group of highly conserved microbial proteins, heat shock proteins (hsps), can be used to effectively prevent and treat arthritis. This protection is mediated through the induction of cross-reactive T cell responses to self-hsps. In JIA, naturally occurring T cell immune responses to hsps are associated with disease remission in restricted oligoarticular JIA. Moreover, those responses are associated with the induction of T cells with a regulatory phenotype. Taken together, these data imply that immune modulation with hsps can be an effective way to restore natural occurring T cell responses, and, thus, treat JIA and rheumatoid arthritis.

Juvenile rheumatoid arthritis

Progress in achieving international consensus concerning the classification of juvenile idiopathic arthritis has been made, although further refinement and validation of these criteria is needed. It is hoped that this will facilitate more effective international collaboration in the study of these diseases, because much remains to be learned about genetic susceptibility, causation, pathogenesis, and treatment. Attention to the unique aspects of chronic arthritis in children such as impaired growth and macrophage activation syndrome may help to reduce disease-related morbidity and mortality. New biologic agents have substantially enhanced the treatment of JRA. The identification of reliable predictors of disease course and outcome is important in the rational and timely application of new therapies.

Juvenile idiopathic arthritis

A significant amount of work has been performed over the past 2 years further defining the pathophysiology of juvenile idiopathic arthritis (JIA). The development of the biologic agent etanercept represents successful translational research. This genetically engineered fusion protein targets tumor necrosis factor, binding and inactivating this important component of inflammation. This advance has been accompanied by refinements in classification, as well as further elucidation of the natural disease course of JIA. Recent work continues to demonstrate the widespread nature of JIA, as well as its severity in adulthood.

The treatment of juvenile arthritis

Until recently, two different classification systems for juvenile arthritis (JA) were utilised, each with its own terminology and subclassification. It has been recognised that particularly within the polyarticular and pauciarticular groups, many distinct subsets exist each with a different prognosis. As a result, a new classification system for JA has been developed. It is hoped that this will allow more accurate assessment of incidence and aetiology of the various subtypes in future generations and in time will allow therapy to be targeted at those most likely to achieve benefit. Since there is a new classification system for JA, the vast majority of published clinical studies were performed using the old classification system. For the purposes of this review, unless otherwise stated, the American College of Rheumatology classification will be used. This is outlined in Table 1 with clinical features of the major subtypes described in Table 3. This review will cover current best practice and discuss future directions for research using the recent advances in the treatment of rheumatoid arthritis (RA) as a model.

Subtyping of juvenile idiopathic arthritis using latent class analysis. British Paediatric Rheumatology Group

OBJECTIVE

To use statistical techniques to identify underlying subtypes of juvenile idiopathic arthritis (JIA) that best explain the observed relationships of clinical and laboratory variables, and to compare the statistically derived subtypes with those defined by the International League of Associations for Rheumatology (ILAR) criteria and examine them for HLA associations.

METHODS

Information on 572 patients diagnosed as having JIA was summarized by 10 clinical and laboratory categorical variables (age at onset, large joint involvement, small joint involvement, polyarthritis, symmetric arthritis, spinal pain, fever, psoriasis, antinuclear antibodies [ANA], and rheumatoid factor). Latent class analysis (LCA) was used to identify underlying ("latent") classes that explained the relationships among the observed variables. Statistical models incorporating 5-8 latent classes were applied to the data.

RESULTS

The 7-class model was the most appropriate. Patterns of joint involvement and the presence of ANA were influential in determining latent classes. There was some correspondence between the latent classes and the ILAR categories, but they did not coincide completely. Significant differences between the latent classes were seen for 3 HLA haplotypes (DRB1*04-DQA1*03-DQB1*03, DRB1*13-DQA1*01-DQB1*06, and DRB1*08-DQA1*0401-DQB1*0402).

CONCLUSION

LCA provides a novel approach to the task of identifying homogeneous subtypes within the umbrella of JIA. In further work, the identified latent classes will be examined for associations with other candidate genes and for differences in outcome.