HLA-DR8 and acute anterior uveitis in ankylosing spondylitis

Unraveling the connection: Uveitis prevalence and risk factors in psoriasis patients - a population-based study

The association between uveitis and spondyloarthropathy (SpA)-related conditions is well-established. However, evidence describing the link between uveitis and psoriasis, and psoriasis without concomitant SpA-related conditions is scarce and conflicting. This large-scale population-based study sought to describe the prevalence and features of uveitis among psoriasis patients in Israel as well as investigating the risk for uveitis in different subgroups of psoriasis patients compared to the general population. We conducted a retrospective study utilizing the electronic database of the Meuhedet Health Maintenance Organization. The study included all patients diagnosed with psoriasis between 2000 and 2020, each patient was matched with four controls based on age, sex, place of residence, and index date. Logistic regression models were employed to assess the association between psoriasis and uveitis while adjusting for the presence of SpA-related conditions. A total of 61 003 psoriasis patients and 244 012 matched controls were included. The prevalence of uveitis was 1.3% versus 1.1% respectively (OR  1.12; 95% CI 1.10-1.30; p < 0.001). When adjusting to psoriasis severity, concurrent SpA, and psoriasis treatment no significant association was found. The rates of uveitis among psoriasis patients with concurrent SpA-related conditions was 3.2% compared to 1.4% in controls without psoriasis or SpA (OR 2.38; 95% CI 2.00-2.83; p < 0.001), while in psoriasis patients without SpA, the rate of uveitis was 1.0% and was similar to controls. Although crude rates of uveitis were higher in patients with severe psoriasis compared to mild psoriasis (2.1% vs. 1.1%), after adjustment, no significant association compared to controls was found in either group. Our findings suggest that the positive association between psoriasis and uveitis is primarily mediated by the coexistence of other SpA-related conditions. These findings imply the presence of a shared pathogenetic mechanism and set the direction for a phenotypic-targeted screening strategy.

Inflammatory arthritis and eye diseases: a Mendelian randomization study

Objectives

The aim of this study was to determine causal associations between inflammatory arthritis and eye diseases (disorders of sclera, cornea, iris, and ciliary body [DSCIC] and disorders of choroid and retina [DCR]).

Methods

Genome-wide association studies' summary data of rheumatoid arthritis (RA) from a large-scale meta-analysis were used to identify genetically predicted RA. UK Biobank source data predicted ankylosing spondylitis (AS), psoriatic arthritis (PsA), and juvenile idiopathic arthritis (JIA). Furthermore, data from the FinnGen Biobank were used to identify genetically predicted eye diseases. Two-sample Mendelian randomization analysis was used to assess the causal relationship between inflammatory arthritis and eye diseases in the European population. Inverse-variance weighting (IVW) was used as the primary method, while MR-Egger, weighted median, and MR-PRESSO outlier test were used to detect heterogeneity and pleiotropy.

Results

Genetically determined RA was indeed observed to have a causal effect on DSCIC (odds ratio [OR] = 1.084, p = 2.353 × 10-10) and DCR (OR = 1.151, p = 1.584 × 10-19). AS was causally associated with DSCIC (OR = 1.068, p < 2.024 × 10-8). In addition, PsA was also found to have a causal association with an increased risk of 17.9% for the development of DSCIC (OR = 1.179, p = 0.003). On the flip side, DSCIC increased the risk of JIA (OR = 2.276, p = 0.003).

Conclusion

Our study provided genetic evidence for the causal associations of RA, AS, and PsA with an increased risk of DSCIC, and a causal association between RA and DCR was also identified. In addition, DSCIC greatly increased the risk of JIA.

Managing Psoriatic Arthritis With Inflammatory Bowel Disease and/or Uveitis

Psoriatic arthritis (PsA) is a chronic inflammatory disease that presents with psoriasis (PsO), peripheral and axial arthropathy. The heterogeneity of disease presentation leads to the term "psoriatic disease (PsD)" which is thought to better encompass the range of clinical manifestations. PsA is associated with several comorbidities such as cardiovascular diseases, metabolic syndrome and other extra-articular manifestations including uveitis, and inflammatory bowel disease (IBD). While novel therapeutics are being developed following advances in our understanding of the pathogenesis of the disease, the diverse combinations of PsA with its various comorbidities still pose a clinical challenge in managing patients with PsA. This article reviews our current understanding of the pathogenesis of PsA and how various pathways in the pathogenesis lead to the two comorbid extra-articular manifestations - uveitis and IBD. We also review current evidence of treatment strategies in managing patients with PsA with comorbidities of uveitis and/or IBD.

Risk factors of uveitis in ankylosing spondylitis: An observational study

BACKGROUND

Uveitis is the most common extra-articular manifestation in patients with ankylosing spondylitis (AS). The prevalence and characteristics of uveitis in AS have been studied in previous literatures, whereas its associated risk factors have not been clarified. Therefore, this study analyzed the risk factors of uveitis in patients with AS.

METHODS

A total of 390 patients with AS who fulfilled the modified New York criteria were enrolled from January to December in 2015. The history of uveitis was accepted only if diagnosed by ophthalmologists. The medical records of the patients were retrospectively reviewed and associated information was collected, such as disease duration, HLA-B27, and the number of peripheral arthritis. Hip-joint lesion was identified by imaging examination. Meanwhile, biochemical examinations were performed to determine the patient's physical function.

RESULTS

Of 390 patients with AS (80.5% male, mean age 33.3 years), 38 (9.7%) had experienced 1 or more episodes of uveitis. The incidence rate for hip-joint lesion was obviously higher for patients with uveitis than the nonuveitis group (44.7% vs 22.2%; P < 0.01). The number of peripheral arthritis was also larger for the uveitis group than nonuveitis group (2.18 ± 0.23 vs 0.55 ± 0.04; P < 0.001). Meanwhile, patients with uveitis had a significantly higher level of antistreptolysin O (ASO) and circulating immune complex (CIC) than those without (P < 0.05 and P < 0.0001, respectively). However, there were no significant differences in disease duration, HLA-B27, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) between the 2 groups. Binary logistic regression results showed that ASO (OR = 12.2, 95% CI:3.6-41.3, P < 0.01) and the number of peripheral arthritis (OR = 4.1, 95%CI:2.6-6.3, P < 0.01) are significantly associated with uveitis in AS.

CONCLUSTION

This study provides some evidence that hip-joint lesion, the number of peripheral arthritis, ASO, and CIC may be associated with higher rates of uveitis in AS. The results of this comprehensive analysis suggest that the possible occurrence of uveitis in AS should not be neglected if the patients have those concomitant risk factors.

Genetic dissection of acute anterior uveitis reveals similarities and differences in associations observed with ankylosing spondylitis

OBJECTIVE

To use high-density genotyping to investigate the genetic associations of acute anterior uveitis (AAU) in patients with and those without ankylosing spondylitis (AS).

METHODS

We genotyped samples from 1,711 patients with AAU (either primary or combined with AS), 2,339 AS patients without AAU, and 10,000 control subjects on an Illumina Immunochip Infinium microarray. We also used data for AS patients from previous genome-wide association studies to investigate the AS risk locus ANTXR2 for its putative effect in AAU. ANTXR2 expression in mouse eyes was investigated by real-time quantitative reverse transcription-polymerase chain reaction.

RESULTS

A comparison between all patients with AAU and healthy control subjects showed strong association over HLA-B, corresponding to the HLA-B27 tag single-nucleotide polymorphism rs116488202. The association of 3 non-major histocompatibility complex loci, IL23R, the intergenic region 2p15, and ERAP1, reached genome-wide significance (P < 5 × 10(-8)). Five loci harboring the immune-related genes IL10-IL19, IL18R1-IL1R1, IL6R, the chromosome 1q32 locus harboring KIF21B, as well as the eye-related gene EYS, were also associated, reaching a suggestive level of significance (P < 5 × 10(-6)). Several previously confirmed AS associations demonstrated significant differences in effect size between AS patients with AAU and AS patients without AAU. ANTXR2 expression varied across eye compartments.

CONCLUSION

These findings of both novel AAU-specific associations and associations shared with AS demonstrate overlapping but also distinct genetic susceptibility loci for AAU and AS. The associations in IL10 and IL18R1 are shared with inflammatory bowel disease, suggesting common etiologic pathways.

Clinical features and major histocompatibility complex genes as potential susceptibility factors in pediatric immune thrombocytopenia

BACKGROUND/PURPOSE

Immune thrombocytopenia (ITP) is a heterogeneous autoimmune disorder with diverse response rates to treatments that include corticosteroids, intravenous immunoglobulins (IVIG), and splenectomy. The predisposing causes of this autoimmune disorder, one of which is immunogenetic susceptibility, have not been fully determined. We investigated whether clinical features and human leukocyte antigen (HLA) genotypes influence the occurrence, treatment response, and disease duration of childhood ITP in Taiwan.

METHODS

We performed HLA genotyping of 70 Taiwanese children with ITP and of 70 healthy controls and compared the data. Demographic data were also collected and evaluated.

RESULTS

The frequencies of heterozygous HLA-A11 and the HLA-Cw1 allele were both significantly decreased in the ITP group (p = 0.0160 and p = 0.0089, respectively), whereas the frequency of heterozygous HLA-DQ5 was significantly increased in the ITP group (p = 0.0057). Patients with HLA-DRB1*11 or -DRB1*15 were more likely to respond poorly to corticosteroids than IVIG (p = 0.0446 and p = 0.0008, respectively). In addition, we observed a positive association between HLA-A11 homozygosity and the development of persistent or chronic ITP [odds ratio (OR) = 6.3165, p = 0.0479]. The presence of HLA-DRB1*08 was, however, negatively correlated with the development of persistent or chronic ITP (OR = 0.1729, p = 0.0657). Children with antecedent of preceding illness (API) and with a younger age of onset were more likely to experience a better treatment response and shorter course of ITP.

CONCLUSION

We suggest that API, age of onset, and particular HLA class I and class II alleles, may be involved in and influence the occurrence and disease duration of childhood ITP, as well as responses to different therapeutic approaches.

Distribution of HLA class I and II genes in ankylosing spondylitis patients from Morocco

OBJECTIVES

In Morocco, the patients affected by ankylosing spondylitis (AS) presents a high frequency of coxitis. Our study reports, for the first time, the polymorphism of Human Leukocyte Antigen (HLA) class I and class II molecules in the Moroccan patients.

METHODS

Forty-six patients diagnosed with an AS and coxitis were compared to a group of 183 healthy controls matched by age, sex and ethnic origin. The HLA typing was performed using microlymphocytotoxicity for the class I (-A, -B) and PCR-SSP for the class II (-DR, -DQ).

RESULTS

We found a significant increase of the HLA-B27 antigen frequency (P<0.0001, RR=20.9) in AS patients (29.3%) compared to the controls (3.2%) and a significant decrease in the frequency of HLA-B12 and HLA-B18 antigens. Examination of HLA class II distribution shows a significant increase of the HLA-DRB1*11 allele frequency in patients (P<0.0001). Concerning HLA-DQB1* alleles, no significant difference between patients and controls was appreciable.

CONCLUSIONS

The HLA-B27 antigen is involved in the predisposition to the AS with coxitis in the Moroccan population. However, the low frequency observed in our population suggests the existence of other genetic and/or environmental factors. Other HLA genes seem to confer a predisposing effect (DRB*11) or a protective effect (B12 and B18) against the disease.

An update on the genetics of HLA B27-associated acute anterior uveitis

The discovery of the association of HLA B27 with spondyloarthropathy led to more questions than answers about the role of this gene in disease susceptibility. The realization that HLA B27 was not responsible for all of the genetic effects helped to lay a foundation for further investigation into the genetics of uveitis. Over several decades, genetic findings have provided clues to advance the understanding of mechanisms of uveitis and to catalyze new research on diagnostics, animal models, and therapies. From the early candidate gene studies on immune mediators to the recent genome-wide investigations, much has been discovered. However, these discoveries have come with the caveat that a genetic finding does not automatically reveal the disease-relevant functional effect of the associated variant.

The effect of HLA‐DR antigens on the susceptibility to, and clinical expression of psoriatic arthritis

OBJECTIVE

To analyse the relative role of HLA-DR antigens in the susceptibility to, and clinical expression of psoriatic arthritis (PsA).

PATIENTS AND METHODS

A retrospective cohort study of 120 patients with PsA who were assessed according to a standard protocol. Patients were classified in accordance with the predominant pattern observed in the last 5 years of disease evolution: polyarthritis (n = 33), oligoarthritis (n = 45), and spondylitis (n = 42). HLA-Cw gene typing was done by the polymerase chain reaction (PCR) sequence-specific oligonucleotide probes (PCR-SSOP) method, while HLA-DR and B27 typing were performed by serological methods. The distribution of HLA-DR and Cw antigens was also analysed in 50 patients with psoriasis alone. One hundred and seventy subjects from our general population served as controls.

RESULTS

No definite association was found between HLA-DR alleles and the risk of psoriasis or PsA. HLA-DR4 was found to be under-represented in arthritic patients [probability (p) = 0.03]. HLA-DR7 showed association with oligoarthritis [odds ratio (OR) 6, 95% confidence interval (CI): 2-16, corrected probability (Pc) = 0.01], whereas HLA-DR8 appeared to be related to the risk of polyarthritis (OR 9.5, 95% CI: 2-42, Pc = 0.02). HLA-Cw*0602 conferred risk for psoriasis (Pc < 0.00001), but not for PsA. As expected, HLA-B27 appeared to be over-represented in patients with spondylitis (p = 0.03).

CONCLUSIONS

This is the first report that associates HLA-DR8 with psoriatic polyarthritis. Although HLA-DR antigens have a marginal role in PsA or psoriasis susceptibility, they may be relevant to the modulation of the clinical expression of PsA. These HLA data add support to the classification of PsA into three disease subsets.

The pathogenesis of ankylosing spondylitis

✓ Ankylosing spondylitis (AS) is a chronic inflammatory disease that can cause significant functional complications by affecting the sacroiliac joints and axial skeleton. Despite a longstanding knowledge about the familial associations of this disease, particularly among patients positive for human leukocyte antigen (HLA)–B27, the fundamental pathogenetic mechanism by which this disease arises in genetically susceptible individuals remains ill defined. Furthermore, the molecular predilection for characteristic articular site involvement remains under ongoing investigation. Current theories about the HLA-B27 association range from the presentation of novel arthritogenic peptides, to abnormal autoimmune stimulation, to anomalous microbial tolerance. The immune effectors of this damage include CD4+, CD8+, and natural killer cells, with marked heterogeneity at different sites. Biomechanical stresses may trigger this disease by exposing the body to previously immune-sequestered autoantigens or by providing a route for bacterial seeding. Environmental triggers such as infection have not been definitively established but may represent a primary pathogenic step in a molecular-mimicry process. In this article, the authors review the current literature on the origin and pathophysiology of AS, focusing on genetic and molecular associations, consequent pathomechanisms, and associated triggers. An improved understanding of the sequence of molecular events that predispose and initiate the onset of this disease will allow for more specific and targeted therapy and better avoidance of the significant side effects of systemic immunomodulation.

Seronegative Spondyloarthropathy – Studies from the Asia Pacific Region

Recent therapeutic advances, in particular the use of anti-tumour necrosis factor (anti-TNF) agents, have revived interest in the seronegative spondyloarthropathies (SpA), a group of arthritides characterised by axial skeletal involvement and the absence of rheumatoid factor. The purpose of this article is to review the studies that have been done in the Asia Pacific region, as a broad understanding of the scope and severity of this group of diseases would enable rheumatologists and physicians in this part of the world to better manage their patients. The majority of genetic studies have focused on the associations of HLA-B27 with ankylosing spondylitis (AS) and SpA, while a few studies examined the associations of the CARD, IL-1, LMP2, TAP and TGF with AS. There are a handful of studies on the immunological responses to bacteria and cytokine levels in AS. The onset and clinical features of SpA have been reported from most countries in the region, but no data on patient outcomes, using current measurement tools such as the Bath Ankylosing Spondylitis Disease Activity index (BASDAI), is available. Validation of these instruments of measurement as well as classification criteria in different ethnic populations is necessary where no prior data exist. Future studies will likely be focused on better clinical characterisation of patient cohorts, particularly with regard to the use of currently used measurement tools for disease activity and spinal function and mobility, and the identification of the need for biologic therapy in each country. Key words: ESSG criteria, Genetics, Immunological and clinical features

Non-B27 MHC associations of ankylosing spondylitis

Ankylosing spondylitis (AS) has been associated with human leukocyte antigen (HLA)-B27 for over 30 years; however, the mechanism of action has remained elusive. Although many studies have reported associations between AS and other genes in the major histocompatibility complex (MHC) in AS, no conclusive results have emerged. To investigate the contribution of non-B27 MHC genes to AS, a large cohort of AS families and controls were B27 typed and genotyped across the region. Interrogation of the data identified a region of 270 kb, lying from 31 952 649 to 32 221 738 base pairs from the p-telomere of chromosome 6 and containing 23 genes, which is likely to include genes involved with susceptibility to AS.

Immunogénétique de la spondylarthrite ankylosante

BACKGROUND

Ankylosing spondylitis (AS) is an inflammatory rheumatic disease with axial involvement but its physiopathology remains unexplained. This latter combines genetic and environmental factors as well as an abnormal immune response.

CURRENT TOPICS AND IMPORTANT RESULT

This review addresses the different aspects of AS immunogenetic. A genetic background in AS is suggested by familial cases, concordance rate in twins and transmission of the disease in siblings. Ankylosing spondylitis is strongly associated with the expression of the HLA Class I antigen, B27, but also with other genes not yet identified since currently, only chromosomic area have been linked to AS. Studies of candidate genes or genome screening allow to determine these chromosomic regions. HLA-B27 is directly associated with the disease physiopathology as suggested by animal models of rats transgenic for human HLA-B27 and beta2 microglobulin. This HLA molecule have original biological properties, in particular a slow heavy chain folding and the formation of heavy chain homodimers without light chain. However, HLA B27 is a functional molecule and assumes its property of presenting peptide of 9 amino acids to CD8+ T cells. Interaction modelling studies between HLA B27 and peptides have identified peptide and peptide groove amino acid sequences, with the identification of critical positions on the HLA B27 molecule for the peptide interaction. Original biochemical properties of HLA-B27 include diminished bacterial antigen response and CD4+ T lymphocyte stimulation. Innate immunity is also of interest in AS, as suggested by the presence of macrophage and polymorphonuclear neutrophils in AS synovitis, as well as the contribution of Toll-like receptors.

FUTURE PROSPECTS AND PROJECTS

Thus in AS, the inflammatory process and then the clinical consequences may be explained by the involvement of HLA-B27, a bacterial antigen presentation, an abnormal immune response and the contribution of innate immunity, T CD4+ but also T CD8+ cells. The original molecular structures of HLA-B27 are certainly involved in this complex physiopathology, but their direct influence on the disease remains to be precised.

Characterization and outcome of uveitis in 350 patients with spondyloarthropathies

This retrospective study analyzed 350 patients with the diagnosis of spondyloarthropathies (SPA) (207 with ankylosing spondylitis (AS), 80 with undifferentiated spondyloarthropathies (USPA) and 63 with psoriatic arthritis (PsA)) attended at a tertiary referral hospital for a minimum period of 5 years. All the patients presented complete clinical (axial and peripheral involvement, heel enthesopathies, extra-articular manifestations) and radiologic (sacroiliac, lumbar, dorsal and cervical spine) evaluation. HLA-B27 and respective alleles were searched. These data were compared with the occurrence of uveitis during the follow-up of the SPA patients. Thirty AS patients (14.5%) presented 55 episodes of acute anterior uveitis; there was statistical association between uveitis and juvenile-onset AS (P = 0.0094) and achillean (P = 0.0003) and plantar (P = 0.0067) enthesopathies; one AS patient presented a single episode of posterior uveitis, associated to tuberculosis. Seven USPA patients (8.8%) presented 13 episodes of acute anterior uveitis; it was not observed statistical association with any variable; one patient presented a single episode of posterior uveitis, associated to toxoplasmosis. Five HLA-B27 positive PsA patients (8%) presented 13 episodes of acute anterior uveitis. All the 26 positive HLA-B27 SPA patients with anterior uveitis tested for the HLA-B27 alleles were HLA-B*2705. No patient presented ophthalmologic severe sequelae of the anterior uveitis. Concluding, anterior uveitis was associated to the juvenile onset of the disease and to the enthesophatic involvement of the lower limbs in AS patients. The HLA-B*2705 allele was predominant in the anterior uveitis patients, whilst posterior uveitis was rare and associated to infectious disease.

The genetic basis of ankylosing spondylitis

PURPOSE OF REVIEW

Genetic factors provide over 90% of the overall susceptibility to ankylosing spondylitis, with about half of the genetic contribution attributed to HLA-B27 and other major histocompatibility complex genes. Recent studies have focused on non-major histocompatibility complex genes. This review is aimed at summarizing the status of major histocompatibility complex and non-major histocompatibility complex genes in ankylosing spondylitis susceptibility, and suggests areas for future studies.

RECENT FINDINGS

A recent meta-analysis of published scans of ankylosing spondylitis susceptibility has confirmed sites on chromosomes 3q, 6p (the major histocompatibility complex), 10q, 16q and 19q in ankylosing spondylitis susceptibility. Non-major histocompatibility complex candidate gene analyses have confirmed a role for the IL-1 gene complex. The search for other non-major histocompatibility complex candidate genes, however, has been complicated by inadequate power in most previous studies. Innovations in genetic methodologies will allow thorough genome wide linkage disequilibrium mapping studies in large cohorts of patients that will result in the dissection of the genetic susceptibility to ankylosing spondylitis.

SUMMARY

Nearly half of the susceptibility to ankylosing spondylitis is provided by major histocompatibility complex genes. Non-major histocompatibility complex genes, most notably the IL-1 gene complex, have been identified and novel technologies promise that a more thorough examination of the rest of the genome will soon elucidate the genetic basis of this disease.

Uveitis

Uveitis is a prevalent disease that mainly affects young people. It leads to a significant number of visual losses. Acute anterior uveitis is the most prevalent form, and it is often associated with spondyloarthritides in which uveitis can be the first manifestation of disease. Precise patterns of uveitis are frequently associated with systemic diseases. Thus, the close collaboration between ophthalmologists and rheumatologists avoids unnecessary diagnostic tests and is essential for the correct assessment and treatment of these patients. Acute anterior uveitis usually has a good prognosis compared with other forms of uveitis. However, it is a cause of disability when flares are frequent. Small prospective studies conducted with sulphasalazine have demonstrated a reduction in the number of flares. Other patterns of uveitis have a worse prognosis, and systemic corticosteroids and/or immunosuppressive drugs are usually required. Infliximab is a promising therapeutic option in selected patients.

Finnish HLA studies confirm the increased risk conferred by HLA-B27 homozygosity in ankylosing spondylitis

OBJECTIVE

To determine the influence of HLA-B27 homozygosity and HLA-DRB1 alleles in the susceptibility to, and severity of, ankylosing spondylitis in a Finnish population.

METHODS

673 individuals from 261 families with ankylosing spondylitis were genotyped for HLA-DRB1 alleles and HLA-B27 heterozygosity/homozygosity. The frequencies of HLA-B27 homozygotes in probands from these families were compared with the expected number of HLA-B27 homozygotes in controls under Hardy-Weinberg equilibrium (HWE). The effect of HLA-DRB1 alleles was assessed using a logistic regression procedure conditioned on HLA-B27 and case-control analysis.

RESULTS

HLA-B27 was detected in 93% of cases of ankylosing spondylitis. An overrepresentation of HLA-B27 homozygotes was noted in ankylosing spondylitis (11%) compared with the expected number of HLA-B27 homozygotes under HWE (4%) (odds ratio (OR) = 3.3 (95% confidence interval, 1.6 to 6.8), p = 0.002). HLA-B27 homozygosity was marginally associated with reduced BASDAI (HLA-B27 homozygotes, 4.5 (1.6); HLA-B27 heterozygotes, 5.4 (1.8) (mean (SD)), p = 0.05). Acute anterior uveitis (AAU) was present in significantly more HLA-B27 positive cases (50%) than HLA-B27 negative cases (16%) (OR = 5.4 (1.7 to 17), p<0.004). HLA-B27 positive cases had a lower average age of symptom onset (26.7 (8.0) years) compared with HLA-B27 negative cases (35.7 (11.2) years) (p<0.0001).

CONCLUSIONS

HLA-B27 homozygosity is associated with a moderately increased risk of ankylosing spondylitis compared with HLA-B27 heterozygosity. HLA-B27 positive cases had an earlier age of onset of ankylosing spondylitis than HLA-B27 negative cases and were more likely to develop AAU. HLA-DRB1 alleles may influence the age of symptom onset of ankylosing spondylitis.

Acute anterior uveitis and HLA-B27

Acute anterior uveitis is the most common form of uveitis. HLA-B27-associated acute anterior uveitis is a distinct clinical entity that has wide-ranging medical significance due to its ocular, systemic, immunologic, and genetic features. The association between HLA-B27 and the spectrum of HLA-B27-associated inflammatory diseases remains one of the strongest HLA-disease associations known to date. This review examines acute anterior uveitis with particular focus on HLA-B27-associated acute anterior uveitis, including the epidemiology, immunopathology, association with HLA-B27 and its subtypes, clinical features, complications, prognosis, and potential new therapies such as anti-TNFalpha therapy and oral HLA-B27-peptide tolerance. There have been substantial recent advances in both clinical and basic scientific research in this field, including studies of the various animal models of acute anterior uveitis and the HLA-B27 transgenic animals, and these are summarized in this review. To the ophthalmologist, HLA-B27-associated acute anterior uveitis is an important clinical entity that is common, afflicts relatively young patients in their most productive years, and is associated with significant ocular morbidity due to its typically recurrent attacks of inflammation and its potentially vision-threatening ocular complications. Furthermore, to the ophthalmologist and the internist, HLA-B27-associated acute anterior uveitis is also of systemic importance due to its significant association with extraocular inflammatory diseases.

Rheumatic diseases in minority populations

Rheumatic diseases are expressed in all ethnic populations, but differ in prevalence, genetic associations, clinical features, and responses to interventions. Most data describing these differences do so in reference to and comparisons with white populations. These are sparse data that evaluate differences within minority populations where there is more homogeneity of external factors, such as social, cultural, and behavioral attitudes. This article reviews the features that are unique to various rheumatic diseases within minority populations.

Spondyloarthritis: update on pathogenesis and management

A great deal of progress has occurred in the past few years in elucidating the causes and designing new treatments for ankylosing spondylitis and other types of spondyloarthritis. In addition to the human leukocyte antigen (HLA)-B27 and other major histocompatibility complex (MHC) genes, chromosomal regions and genes elsewhere in the genome are being implicated both in disease susceptibility and severity. The various ways HLA-B27 may function in causing spondyloarthritis now are better understood to encompass not only antigen presentation but also other mechanisms, possibly all being operative in pathogenesis (misfolding of the HLA-B27 molecule, impaired intracellular killing of bacteria, and HLA-B27 itself serving as an autoantigen). Specific enteric and sexually acquired infections can trigger reactive arthritis, though no specific microbe has been identified in other forms of spondyloarthritis. Intestinal inflammation with impairment of the gut:blood barrier may be operative in driving ankylosing spondylitis and enteropathic arthritis. A number of treatments have been tried in spondyloarthritis, including older agents such as methotrexate and sulfasalazine but also newer drugs such as pamindronate. The recent introduction of tumor necrosis factor (TNF) blockers in the treatment of spondyloarthritis has offered the most hope in not only relieving symptoms and signs of both peripheral arthritis and enthesitis but also spinal disease, which often has been refractory to other agents. Their high cost and considerable side effect profile, however, have necessitated the establishment of guidelines for their use in these diseases in order to target the patient in whom they are likely to have the most benefit.

Effect of HLA-B and HLA-DR genes on susceptibility to and severity of spondyloarthropathies in Mexican patients

OBJECTIVE

To investigate the role of HLA-B and HLA-DR genes as contributors to genetic susceptibility and clinical expression of the spondyloarthropathies (SpA) in the Mexican population.

METHODS

The study included 172 patients with SpA (undifferentiated SpA 83, ankylosing spondylitis (AS) 64, and reactive arthritis 25) and 99 healthy controls. The HLA-B and HLA-DR alleles were detected by the polymerase chain reaction with sequence-specific primers technique. Patient assessment included demographic data, diagnostic categories, and disease patterns. Statistical methods included the Mantel-Haenzel chi(2) test, Fisher's exact test, and Woolf method for odds ratio (OR). Differences of continuous variables between HLA allele groups were calculated by Student's t test.

RESULTS

Increased frequencies of HLA-B27 (pCh10(-3), OR=28.7), HLA-DR1 (pC=0.045, OR=2.77), and HLA-B15 (p=0.034, pC=NS, OR=2.04) alleles in the whole group were found. HLA-B27 strength of association (OR) was 41.4 in AS; 20.9 in undifferentiated SpA; 27.2 in reactive arthritis. HLA-DR1 and HLA-B15 were increased in undifferentiated SpA (pC=0.045, OR=2.98 and p=0.004, pC=NS, OR=2.75). By analysing 58 HLA-B27 negative patients it was found that HLA-B15 and HLA-DR1 associations with SpA were independent of HLA-B27; increased frequencies of HLA-B15 were found in the whole SpA group and in patients with undifferentiated SpA (pC=0.03, OR=3.09 and pCh0.01, OR=3.77) and of HLA-DR1 in the latter (p=0.04, pC=NS, OR=3.15). HLA-B27 positive patients were younger than HLA-B27 negative patients at onset (p=0.03), but HLA-DR1 positive patients were older than HLA-DR1 negative patients (p=0.03). Bath indices for disease activity and functioning were higher in HLA-B27 positive patients (p=0.006 and p=0.004 v HLA-B27 negative patients). In contrast, neither HLA-DR1 nor HLA-B15 influenced these indices.

CONCLUSION

Apart from HLA-B27, there is a significant association of HLA-DR1 and HLA-B15 with SpA in Mexicans which is independent of B27. HLA-B27 is associated with younger age at onset and increased disease severity and HLA-DR1 with older age at onset. The strength of HLA-B15, HLA-B27, and HLA-DR1 associations varied in different forms of SpA.

Genetic aspects of susceptibility, severity, and clinical expression in ankylosing spondylitis

While twin studies have previously demonstrated high heritability of susceptibility to ankylosing spondylitis (AS), it is only recently that the involvement of genetic factors in determining the severity of the disease has been demonstrated. The genes involved in determining the rate of ankylosis in AS are likely to be different from those involved in the underlying immunologic events, and represent important potential targets for treatment of AS. This article will describe the progress that has been made in the genetic epidemiology of AS, and in identifying the genes involved.

Clinical features and predictive factors in psoriatic arthritis-related uveitis

OBJECTIVES

To analyze the clinical features of uveitis in psoriatic arthritis (PsA) and to investigate the factors predicting its appearance.

PATIENTS AND METHODS

Retrospective cohort study (1991-2000) of 71 patients diagnosed with PsA according to the criteria of Moll and Wright. All patients were studied according to a standard protocol. The group was divided into 3 articular categories: axial, oligoarticular, and polyarticular. Human leukocyte antigen (HLA)-Cw typing was performed by the polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) method in 65 patients and in 177 healthy donors. HLA-DR typing was done by serologic methods in the 71 patients and in 82 healthy donors from the same racial and geographic origin. The HLA-B27 allele also was tested among the study population. All subjects with possible inflammatory ocular disease received a complete ophthalmologic examination at the Ophthalmology Department of our hospital. Only patients with uveitis were analyzed. Univariate and multivariate analyses were applied.

RESULTS

Thirteen patients had uveitis (18% of this series), 4 (31%) had an insidious onset, and the remaining had acute-onset uveitis. Five cases (39%) had bilateral-simultaneous uveitis. Ten (77%) presented with anterior uveitis only, 2 with anterior and posterior pole involvement, and only 1 case with isolated posterior pole involvement. Four patients needed oral corticosteroids; 2 of them also used immunosuppresive drugs. None of our patients developed sequelae or complications. In univariate analysis, uveitis was associated with inflammatory back pain (P =.02), sacroiliac pain (P =.001), syndesmophytes (P =.001), bilateral sacroileitis (P =.0001), HLA-DR13 (P =.002), and HLA-B27 (P =.026). In multivariate analysis, the predictive factors for uveitis were bilateral sacroileitis (OR 17, 95% CI: 3.7-76, P =.0002), HLA-DR13 (OR 24, 95% CI: 3.78-150, P =.0056), and syndesmophytes (OR 9.7, 95% CI: 0.97-97, P =.05).

CONCLUSIONS

Insidious onset, bilaterality, posterior pole involvement, and chronicity are common in PsA patients with uveitis. In this study, extensive axial involvement (bilateral sacroileitis and syndesmophytes), and the HLA-DR13 antigen were the best predictors for the appearance of uveitis.

HLA-A*9, a probable secondary susceptibility marker to ankylosing spondylitis in Basque patients

HLA-B27 is strongly associated to ankylosing spondylitis (AS). The objective of our study was to analyze HLA-B27 association, B27 subtype distribution and frequency of other HLA class I and DR antigens in a group of Basque AS patients. HLA class I antigens were typed serologically and HLA-B27 and A9 subtypes were determined by DNA typing in samples from 46 patients with AS, 54 B27-positive spondyloarthropathies, 82 healthy subjects and 20 B27-positive controls. A class I HLA 9.2 kb PvuII restriction fragment length polymorphism (RFLP), previously associated with AS, was analyzed in a representative group of patients and controls. We found that HLA-B*2705 conferred a relative risk of 126 for AS in this group. HLA-A9 (A*2402) allele was significantly increased in AS patients compared with healthy controls and B27-positive control group (Pcorr<0.0001) and also increased in patients affected with peripheral arthritis. No association between class I HLA 9.2 Kb RFLP and AS was found. These results suggest that HLA-A*9 allele itself or another linked gene could act as a secondary and independent susceptibility allele to AS.

The immunogenetics of the seronegative spondyloarthropathies

In none of the rheumatic diseases has the genetic contribution to pathogenesis been so well characterized as in the seronegative spondyloarthropathies. Most important has been the elucidation of the structure and effect on disease expression of HLA-B27, where 11 subtypes have been distinguished to date. These vary in frequency in different ethnic groups and seem to show differential disease associations. The high frequency of this gene in patients with the seronegative spondyloarthropathies, especially ankylosing spondylitis (AS) and Reiter's syndrome (RS)/reactive arthritis (ReA), has emerged as probably the best example of a disease association with a hereditary marker. Other HLA genes, in addition to HLA-B27, have been implicated in psoriasis and psoriatic arthritis. These include those from the HLA-C locus and from HLA-DR. In addition, recent family studies have implicated other genes outside the MHC that further enhance the susceptibility to AS.

Eye involvement in the spondyloarthropathies

Eye inflammation, especially uveitis, is a prominent feature of spondyloarthropathies. Uveitis associated with ankylosing spondylitis and Reiter's syndrome usually is a unilateral acute anterior uveitis with a high tendency to recur sometimes in the contralateral eye. Uveitis associated with undifferentiated spondyloarthropathy, inflammatory bowel disease, and psoriasis may be less characteristic in its presentation, with a higher tendency to posterior pole involvement, bilaterality, and chronicity. Although acute anterior uveitis is grouped into the spectrum of human leukocyte antigen B27-related disease, other genetic and environmental factors including infections by gram-negative bacteria and gut inflammation can play a role in its pathogenesis. The prognosis of uveitis usually is excellent with topical treatment, and only those with posterior pole involvement or a high tendency to recur or to chronicity might benefit from immunosuppressive therapy.

Animal models of human leukocyte antigen B27-linked arthritides

The major histocompatibility complex class I allele human leukocyte antigen (HLA) B27 is strongly associated with human spondyloarthropathies. To date, 12 subtypes of HLA-B27 are known and most of them are linked with human spondyloarthropathies in different ethnic populations. Although these subtypes differ from each other by a few amino acids, the have an identical B pocket in the base of the antigen-binding groove. Considering the structure of HLA-B27 subtypes and their peptide binding specificity, it is important to consider their role as antigen-presenting molecules. Many B27-linked diseases begin after an infection with an enterobacteria, suggesting a role for environmental antigens in addition to an HLA-B27 molecule. To delineate the role of infection, studies have been carried out in animal models of reactive arthritidis. More recently, transgenic animal models have been used to understand the handling of environmental antigens by HLA-B27 molecule. This article discusses some of these transgenic and nontransgenic animal models of human diseases.

HLA-B27 and the seronegative spondyloarthropathies

In the 25 years since the initial reports of the association of HLA-B27 with ankylosing spondylitis (AS) and subsequently with Reiter's syndrome, psoriatic spondylitis, and the spondylitis of inflammatory bowel disease, the association of HLA-B27 with the seronegative spondyloarthropathies has remained one of the best examples of a disease association with a hereditary marker. HLA-B27 has been recognized as representative of a spectrum of diseases, ranging from the majority of HLA-B27-positive individuals who have no disease at all, through those with isolated eye or skin involvement, to those with critical eye, heart, and peripheral joint compromise of full-blown AS. Yet HLA polymorphism has evolved in response to environmental stresses, and even the presence of HLA-B27 itself appears to confer advantages in certain infectious diseases, such as acquired immune deficiency syndrome (AIDS). This article will review what is currently known about HLA-B27 and disease, especially in the seronegative spondyloarthropathies. The structure-function relationship of HLA-B27 will be presented, including differences between the B27 subtypes both in their ethnic variation and possible disease implications. The disease spectrum conferred by the presence of HLA-B27 will also be discussed, and the theories of how HLA-B27 contributes to the pathogenesis of the spondyloarthropathies will be considered.

The effect of HLA-DR genes on susceptibility to and severity of ankylosing spondylitis

OBJECTIVE

To analyze the effect of HLA-DR genes on susceptibility to and severity of ankylosing spondylitis (AS).

METHODS

Three hundred sixty-three white British AS patients were studied; 149 were carefully assessed for a range of clinical manifestations, and disease severity was assessed using a structured questionnaire. Limited HLA class I typing and complete HLA-DR typing were performed using DNA-based methods. HLA data from 13,634 healthy white British bone marrow donors were used for comparison.

RESULTS

A significant association between DR1 and AS was found, independent of HLA-B27 (overall odds ratio [OR] 1.4, 95% confidence interval [95% CI] 1.1-1.8, P = 0.02; relative risk [RR] 2.7, 95% CI 1.5-4.8, P = 6 x 10(-4) among homozygotes; RR 2.1, 95% CI 1.5-2.8, P = 5 x 10(-6) among heterozygotes). A large but weakly significant association between DR8 and AS was noted, particularly among DR8 homozygotes (RR 6.8, 95% CI 1.6-29.2, P = 0.01 among homozygotes; RR 1.6, 95% CI 1.0-2.7, P = 0.07 among heterozygotes). A negative association with DR12 (OR 0.22, 95% CI 0.09-0.5, P = 0.001) was noted. HLA-DR7 was associated with younger age at onset of disease (mean age at onset 18 years for DR7-positive patients and 23 years for DR7-negative patients; Z score 3.21, P = 0.001). No other HLA class I or class II associations with disease severity or with different clinical manifestations of AS were found.

CONCLUSION

The results of this study suggest that HLA-DR genes may have a weak effect on susceptibility to AS independent of HLA-B27, but do not support suggestions that they affect disease severity or different clinical manifestations.

Increase of HLA-DRB1*0408 and -DQB1*0301 in HLA-B27 positive reactive arthritis

OBJECTIVE

To study HLA class II association in reactive arthritis.

METHODS

63 patients with reactive arthritis and 46 with rheumatoid arthritis were included in the study. HLA-DR alleles were determined by using a sequence specific PCR method. Oligonucleotide hybridisation was used for definition of DRB1*04 subtypes and DQB1 alleles. HLA-B27 was determined by standard microcytotoxity test or by PCR. HLA-B27 subtyping was made by sequencing.

RESULTS

46 (73%) of 63 patients with reactive arthritis were HLA-B27 positive and 24 (38%) were HLA-DRB1*04 positive. When haplotypes were inferred according to the known associations between DRB1 and DQB1 alleles, the frequency of DRB1*04-DQB1*0301 haplotype was found to be 13% (12/92) in HLA-B27 positive reactive arthritis patients, in contrast to 0% in HLA-B27 negative reactive arthritis (P = 0.04) and 1% in random controls (P = 0.0009). However, this combination was also found in 5% of 84 HLA-B27 positive control haplotypes, showing a linkage disequilibrium between B27 and this particular class II haplotype. HLA-DRB1*0408 subtype was found in 8/24 (33%) of the HLA-DRB1*04 alleles in patients with reactive arthritis, accounting for most DQB1*0301 haplotypes, but only in 5/55 (9%) of the DRB1*04 alleles in random controls (P = 0.017). All reactive arthritis patients with this subtype were positive for HLA-B27. DRB1*04-DQB1*0302 haplotype was increased in patients with rheumatoid arthritis (28/92, 30%) compared with reactive arthritis (12/126, 10%) or with the controls (12/100, 12%; P = 0.003). HLA-B*2705 was by far the dominant B27 subtype both in reactive arthritis patients with the particular DRB1*0408-DQB1*0301 haplotype and in controls. It was found in 11 out of 12 DR analysed patients, as well as in 10 out of 11 randomly selected B27 positive controls.

CONCLUSIONS

Although no single class II allele was found to be increased among patients with reactive arthritis, HLA-B27, DRB1*0408, and DQB1*0301 might exert a haplotypic effect in the pathogenesis of reactive arthritis, or they may be markers of a subset of B27 haplotypes conferring susceptibility.