HL-A 27 and arthropathies associated with ulcerative colitis and psoriasis

Clinical Characteristics of HLA-B27-Associated Anterior Uveitis in a Finnish Population-Based Cohort

PURPOSE

To evaluate the clinical characteristics, treatment outcomes and ocular complications in patients with HLA-B27-associated AU compared to those without HLA-B27.

METHODS

From the population-based data of all adult patients with AU during 2009-2020 (n = 413), 241 patients tested for HLA-B27 were included. Age of the initial onset, gender, etiology, course of uveitis, visual outcomes and complications were studied.

RESULTS

170 patients (71%) were HLA-B27+ and 71 (29%) HLA-B27-. Mean age at uveitis onset was 37 ± 13 in HLA-B27+ (95% CI, 35.4-39.3) and 43 ± 14 (95% CI, 40.3-46.4) in HLA-B27- patients (p = 0.001). Male:female ratio was 1.1:1 among HLA-B27+ and 0.58:1 (p = 0.024) in HLA-B27- patients. Most patients, 63% in HLA-B27+ and 68% in HLA-B27- had chronic uveitis. Recurrences were noted in 31% in HLA-B27+ group compared to 13%in HLA-B27-. 51% and 17% of HLA-B27+ and HLA-B27- patients, respectively, had systemic disease-associated uveitis. Etiology was Idiopathic in 44% and 69% of HLA-B27+ and HLA-B27- patients, respectively (p < 0.001). After the follow-up, +2 and -4 ETDRS letters changes were noted in HLA-B27+ and HLA-B27- patients (p = 0.005). Ocular complications developed in 43% and 47%, and surgical treatment of complications was required in 20% and 33% of patients in HLA-B27+ and HLA-B27- patients (p = 0.009). 1% (HLA-B27+) and 3% (HLA-B27-) developed visual impairment.

CONCLUSION

Our results highlight the differences in the age of uveitis onset, gender distribution, course of uveitis, etiology, and treatment outcomes in HLA-B27+ and HLA-B27-uveitis. HLA-B27 seems to be associated with younger age at uveitis onset, more recurrences, systemic diseases, and better treatment outcomes with less complications.

Crohn's disease and clinical management today: How it does?

Crohn's Disease (CD) is an Inflammatory Bowel Disease and is characterized by an immune-mediated nature. Its etiology results from the interaction between genetic, enviromental and microbial factors. Regarding pathophysiology, it involves high levels of interleukin (IL)-12, IL-17, and Th1 profile, along with loss of tolerance mechanisms, an increase in pro-inflammatory interleukins, beyond the possibility to affect any part of the gastrointestinal tract. Its symptoms include abdominal pain, chronic diarrhea, weight loss, anorexia, and fatigue, as well as blood in the stool or rectum. Additionally, conditions comprising musculoskeletal, cutaneous, ocular, hepatic, and hematological alterations may be associated with this scenario and extra-intestinal presentation, such as erythema nodosum, anterior uveitis, osteoporosis, and arthritis can also occur. Today, clinical history, exams as fecal calprotectin, ileocolonocopy, and capsule endoscopy can be performed in the diagnosis investigation, along with treatments to induce and maintain remission. In this sense, anti-inflammatory drugs, such as corticosteroids, immunomodulators, and biological agents, as well as surgery and non-pharmacological interventions plays a role in its therapy. The aim of this review is to bring more current evidence to clinical management of CD, as well as to briefly discuss aspects of its pathophysiology, surveillance, and associated disorders.

Autoimmune alleles at the major histocompatibility locus modify melanoma susceptibility

Autoimmunity and cancer represent two different aspects of immune dysfunction. Autoimmunity is characterized by breakdowns in immune self-tolerance, while impaired immune surveillance can allow for tumorigenesis. The class I major histocompatibility complex (MHC-I), which displays derivatives of the cellular peptidome for immune surveillance by CD8+ T cells, serves as a common genetic link between these conditions. As melanoma-specific CD8+ T cells have been shown to target melanocyte-specific peptide antigens more often than melanoma-specific antigens, we investigated whether vitiligo- and psoriasis-predisposing MHC-I alleles conferred a melanoma-protective effect. In individuals with cutaneous melanoma from both The Cancer Genome Atlas (n = 451) and an independent validation set (n = 586), MHC-I autoimmune-allele carrier status was significantly associated with a later age of melanoma diagnosis. Furthermore, MHC-I autoimmune-allele carriers were significantly associated with decreased risk of developing melanoma in the Million Veteran Program (OR = 0.962, p = 0.024). Existing melanoma polygenic risk scores (PRSs) did not predict autoimmune-allele carrier status, suggesting these alleles provide orthogonal risk-relevant information. Mechanisms of autoimmune protection were neither associated with improved melanoma-driver mutation association nor improved gene-level conserved antigen presentation relative to common alleles. However, autoimmune alleles showed higher affinity relative to common alleles for particular windows of melanocyte-conserved antigens and loss of heterozygosity of autoimmune alleles caused the greatest reduction in presentation for several conserved antigens across individuals with loss of HLA alleles. Overall, this study presents evidence that MHC-I autoimmune-risk alleles modulate melanoma risk unaccounted for by current PRSs.

Long term complications and vision loss in HLA-B27 uveitis

OBJECTIVES

To evaluate the long term complications and vision loss in HLA-B27 uveitis.

METHODS

Retrospective review of subjects with HLA-B27 uveitis in a public tertiary centre between January 2008 and 2020.

RESULTS

562 HLA-B27-positive subjects (834 eyes) had mean follow-up of 9.8 years (8173.2 eye-years). Median visual acuity at ten years was 0.1 logMAR (IQR 0.0-0.1). Complications occurred in 404 eyes (48.4%): posterior synechiae (39.7%), cataract (22.1%), elevated intraocular pressure (15.5%), cystoid macular oedema (6.0%). Permanent moderate vision loss ( ≤ 0.4 logMAR) due to uveitis occurred in 14 eyes (1.7%) and severe vision loss (≤ 1.0 logMAR) in 7 eyes (0.8%). Complications were more common with older age (OR 1.017 p = 0.016), chronic inflammation (OR 5.272 p < 0.001) and intermediate uveitis (OR 5.982 p < 0.001).

CONCLUSIONS

Complications are frequent in HLA-B27 uveitis, especially in older subjects, chronic inflammation and intermediate uveitis. Despite this, the majority of subjects maintain good visual prognosis.

MHC class I associations beyond HLA-B27: the peptide binding hypothesis of psoriatic arthritis and its implications for disease pathogenesis

PURPOSE OF REVIEW

To provide an overview of the heterogeneous human leucocyte antigen (HLA) associations of psoriatic arthritis, their relationship to particular clinical features of the disease, and how a hypothesis of binding specific peptides could provide a unifying basis for this heterogeneity.

RECENT FINDINGS

There have been substantive advances in understanding the role of HLA molecules in binding self-peptides that select our repertoire of T cells, the specific peptide-binding properties of these HLA allotypes, and their crystallographic structure. These advances provide a means to envision the significance of the heterogeneous psoriatic arthritis HLA associations. The clinical relevance of these allotypes if heightened by emerging knowledge of their relationship to particular clinical features of the disease that serve as subphenotypes.

SUMMARY

We propose a peptide binding hypothesis of psoriatic arthritis based on a shared pattern of negative charge in the 'B' pocket of the HLA-B and HLA-C molecules encoded by the susceptibility allotypes. This hypothesis suggests that peptides characterized by the presence of arginine at position 2 or 3 are bound to the susceptibility allotypes and drive the T-cell clones selected on them to attack molecules containing these peptides located in sites of psoriatic arthritis inflammation.

The arthritis connection to inflammatory bowel disease (IBD): why has it taken so long to understand it?

Inflammatory bowel disease (IBD) associated arthritis is a subgroup of spondyloarthritis (SpA) that has suffered from lack of recognition in rheumatology clinical and research circles for over 100 years. Although clinically distinguishable from rheumatoid arthritis and ankylosing spondylitis, it took advances in detection systems in the middle of the last century (rheumatoid factor, HLA-B27) to convincingly make the final separations. We now know that significant numbers of patients with SpA have associated clinical IBD and almost half of them show subclinical gut inflammation, yet the connection between the gut and the musculoskeletal system has remained a vexing problem. Two publications from Nathan Zvaifler (one in 1960, the other in 1975) presciently described the relationship between the gut and the spine/peripheral joints heralding much of the work present today in laboratories around the world trying to examine basic mechanisms for the connections (there are likely to be many) between the gut, the environment (presumably our intestinal flora) and the downstream effect on the musculoskeletal system. The role of dysregulated microbiome along with microbiome-driven T helper 17 cell expansion and immune cell migration to the joints has been recognised, all of which occur in the appropriate context of genetic background inside and outside of the human leucocyte antigen system. Moreover, different adhesion molecules that mediate immune cells homing to the gut and joints have been noted. In this review, we studied the origins and evolution of IBD-arthritis, proposed pathogenic mechanisms and the current gaps that need to be filled for a complete understanding of IBD-arthritis.

Interleukin-17A biomarker as a predictor for detection of early axial spondyloarthritis changes in patients with psoriasis

AIM

Although the pathogenic mechanisms of psoriatic arthritis (PsA) are not completely clarified, evidence suggests that interleukin 17A (IL-17A)-mediated immune responses play a pivotal role in the disease. This is best underscored by the important clinical effectiveness of IL-17A inhibitors in psoriasis treatment. We aim to investigate the predictive value of IL-17A in detecting the early axial spondyloarthropic (SpA) changes in psoriatic patients.

METHODS

The study enrolled 100 patients with psoriasis, classified into group 1, included 62 patients with only psoriatic skin lesions (Ps), and group 2 included 38 patients with PsA, and 100 age and gender matched healthy volunteers. All participants were subjected to general and local clinical examination, laboratory assessment including IL-17A in the serum by means of enzyme-linked immunosorbent assay, and axial joint radiological assessment.

RESULTS

Our study included 60 males (60%) and 40 females (40%).The positive radiological findings of early axial SpA changes were found among 30.6% of the Ps group and among 84.2% of the PsA group. There were significant differences between patients with positive magnetic resonance imaging (MRI) findings of early axial SpA and patients with negative MRI findings in both groups regarding IL-17A levels. There was a significant association between IL-17A level and early axial SpA changes in psoriatic patients with a clear cutoff point (222.5).

CONCLUSION

Our study can imply that IL-17A is a valuable, useful and low-cost biomarker in detecting early axial SpA changes in asymptomatic and nonradiographic axial SpA (nr-axial SpA) psoriatic patients that helps early management and prevent progressive axial involvement and disabilities.

Psoriatic arthritis: A systematic review of non-HLA genetic studies and important signaling pathways

Psoriatic arthritis (PsA) is a common, chronic inflammatory disease with complex pathogenesis. In recent years, a number of susceptibility non-human leukocyte antigen (HLA) genes of PsA have been revealed, which also act as important factors in the pathogenesis of PsA as well as HLA genes. By searching the databases National Center for Biotechnology Information, Google and PubMed, 37 articles are included and 50 susceptibility non-HLA genes for PsA are presented, such as IL23A, TNIP1, TYK2, STAT4, IL12B, RUNX3 and TRAF3IP2. In these non-HLA genes, some are common genes shared with other diseases, whereas most of these susceptibility genes are related to the pathogenesis of PsA by activation or inhibition of the signaling pathways. Several signaling pathways possibly implicated in the pathogenesis of PsA are introduced in this paper, including the 2 mainly signaling pathways, IL23/Th17 signaling pathway and NF-κB signaling pathway, and the other involved signaling pathways, such as JAK-STAT signaling pathway and MAPK signaling pathway.

Axial psoriatic arthritis: An update for dermatologists

Psoriasis is a chronic, immune-mediated, systemic, inflammatory disorder characterized by skin plaques and, often, nail disease and arthritis that contribute to reduced quality of life. Psoriatic arthritis-a heterogeneous, inflammatory, musculoskeletal disease that can cause permanent damage to both peripheral and axial joints-is the most common comorbidity of psoriasis. Axial disease occurs in 25% to 70% of patients with PsA, with some patients exclusively experiencing axial joint involvement. Early therapeutic intervention is important for preventing permanent joint and spine damage and loss of functionality in these patients. Because skin symptoms associated with psoriasis often precede psoriatic arthritis, dermatologists are uniquely positioned to play an important role in identifying and treating patients with psoriatic arthritis. Proactive screening of patients with all severities of psoriasis for the signs and symptoms of psoriatic arthritis is key to early diagnosis and intervention. In this review, we discuss the clinical presentation, risk factors, and treatment options for psoriatic arthritis with axial involvement, with the aim of helping dermatologists understand the disease and identify patients who might benefit from further assessment, treatment, and/or referral to a rheumatology practice.

Defining the phenotype, pathogenesis and treatment of Crohn's disease associated spondyloarthritis

Peripheral and axial spondyloarthritis are the most common extra-intestinal manifestations reported in patients with Crohn's disease. Despite the frequency of Crohn's disease associated spondyloarthritis, clinical diagnostic tools are variably applied in these cohorts and further characterization with validated spondyloarthritis disease activity indexes are needed. In addition, the pathogenesis of Crohn's disease associated spondyloarthritis is not well understood. Evidence of shared genetic, cellular, and microbial mechanisms underlying both Crohn's disease and spondyloarthritis highlight the potential for a distinct clinicopathologic entity. Existing treatment paradigms for Crohn's disease associated spondyloarthritis focus on symptom control and management of luminal inflammation. A better understanding of the underlying pathogenic mechanisms in Crohn's disease associated spondyloarthritis and the link between the gut microbiome and systemic immunity will help pave the way for more targeted and effective therapies. This review highlights recent work that has provided a framework for clinical characterization and pathogenesis of Crohn's disease associated spondyloarthritis and helps identify critical gaps that will help shape treatment paradigms.

IL-17 in the immunopathogenesis of spondyloarthritis

Spondyloarthritis (SpA) is a term that refers to a group of inflammatory diseases that includes psoriatic arthritis, axial SpA and nonradiographic axial SpA, reactive arthritis, enteropathic arthritis and undifferentiated SpA. The disease subtypes share clinical and immunological features, including joint inflammation (peripheral and axial skeleton); skin, gut and eye manifestations; and the absence of diagnostic autoantibodies (seronegative). The diseases also share genetic factors. The aetiology of SpA is still the subject of research by many groups worldwide. Evidence from genetic, experimental and clinical studies has accumulated to indicate a clear role for the IL-17 pathway in the pathogenesis of SpA. The IL-17 family consists of IL-17A, IL-17B, IL-17C, IL-17D, IL-17E and IL-17F, of which IL-17A is the best studied. IL-17A is a pro-inflammatory cytokine that also has the capacity to promote angiogenesis and osteoclastogenesis. Of the six family members, IL-17A has the strongest homology with IL-17F. In this Review, we discuss how IL-17A and IL-17F and their cellular sources might contribute to the immunopathology of SpA.

The role of IL-17A in axial spondyloarthritis and psoriatic arthritis: recent advances and controversies

Although the pathogenic mechanisms underlying axial spondyloarthritis (axSpA) and psoriatic arthritis (PsA) are not fully elucidated, several lines of evidence suggest that immune responses mediated by interleukin 17A (IL-17A) play a pivotal role in both diseases. This is best highlighted by the significant clinical efficacy shown with inhibitors of IL-17A in treating axSpA and PsA. Nevertheless, a number of knowledge gaps exist regarding the role of IL-17A in the pathophysiology of spondyloarthritis in man, including its cellular origin, its precise role in discrete disease processes such enthesitis, bone erosion, and bone formation, and the reasons for the discrepant responses to IL-17A inhibition observed in certain other spondyloarthritis manifestations. In this review, we focus on the latest data from studies investigating the role of IL-17A in ankylosing spondylitis (AS) and PsA that build on existing and emerging scientific knowledge in the field. Key remaining research questions are also highlighted to guide future research.

Fecal transplants in spondyloarthritis and uveitis: ready for a clinical trial?

PURPOSE OF REVIEW

The intestinal microbiome is thought to play a role in the pathogenesis of inflammatory bowel disease (IBD). There are many shared clinical manifestations between IBD and spondyloarthritis (SpA), of which the most common are peripheral arthritis and uveitis. Clinical overlap along with similar genetics between these diseases suggests a possible shared pathogenetic mechanism, which might center on the intestinal microbiota. In this review, we discuss the available evidence that SpA is a microbiome-driven disease and indicate how SpA-associated uveitis could be tied to gut dysbiosis. We conclude by discussing different treatment paradigms targeting the intestinal microbiome for SpA.

RECENT FINDINGS

Recent studies support the growing evidence of the intestinal microbiome as a crucial player in SpA disease pathogenesis. There is emerging evidence that the gut microbiome may play a causative role in uveitis.

SUMMARY

The field is beginning to discover a new level of understanding how the intestinal microbiome is involved in SpA. Treatment methods to alter intestinal microbiota to treat SpA-related diseases are still in its infancy.

Etiological and Clinical Characteristics of HLA-B27-associated Uveitis in a Tertiary Referral Center

Objectives

To investigate the demographic, etiologic, and clinical features of HLA-B27-associated uveitis.

Materials and Methods

The clinical records of 91 patients diagnosed with HLA-B27-associated uveitis at the Ulucanlar Eye Training and Research Hospital between the years of 2005 and 2016 were reviewed. Each patient’s presenting complaints, best-corrected visual acuities in first and last visits, biomicroscopic and fundoscopic examination findings, frequency and seasonal distribution of attacks, and demographic data such as age and sex were noted. Therapeutic approaches, duration of follow-up, and complications were analyzed.

Results

A total of 91 patients (179 eyes) aged 19-82 years (mean age 46.52±13.06 years) were included. Forty-three patients (47.3%) were female and 48 (52.7%) were male. Bilateral involvement was observed in 44 (48.4%) and unilateral involvement was observed in 47 (51.6%) patients. The most frequent complaint was redness (67%), followed by decreased and/or blurred vision (50.5%). The mean follow-up time was 38.2 months (range, 1-245 months). Anterior uveitis was most common anatomical subtype, seen in 86 (94.5%) of the patients. Mean number of attacks was 1.93±1.45 per patient-year and a significantly higher number of uveitis attacks (47%) occurred in winter. Twenty-four patients (26.3%) were diagnosed with ankylosing spondylitis. Fibrinous uveitis was detected in 36 patients (39.5%). Posterior synechia developed in 41 (22.9%) and hypopyon developed in 7 (3.9%) eyes. The most common complications were cataract (n=12, 6.7%) and ocular hypertension (n=15, 8.3%).

Conclusion

Ninety-one (6.3%) of the 1422 patients followed in our uvea clinic were diagnosed with HLA-B27-associated uveitis. HLA-B27-associated uveitis is characterized by acute, recurring sudden-onset iridocyclitis with a moderate to severe amount of fibrin and cells in the anterior chamber, and is easily treatable. Visual prognosis is good despite the complications.

Role of Human Leukocyte Antigens (HLA) in Autoimmune Diseases

Since the discovery of HLA 60 years ago, it has contributed to the understanding of the immune system as well as of the pathogenesis of several diseases. Aside from its essential role in determining donor-recipient immune compatibility in organ transplantation, HLA genotyping is meanwhile performed routinely as part of the diagnostic work-up of certain autoimmune diseases. Considering the ability of HLA to influence thymic selection as well as peripheral anergy of T cells, its role in the pathogenesis of autoimmunity is understandable. The aim of this paper is to provide a brief overview of the role and current clinical relevance of HLA-B27 in spondyloarthritis and HLA-B51 in Behçet's disease as well as HLA-DQ2/DQ8 in celiac disease and HLA-DRB1 in rheumatoid arthritis and to discuss possible future implications.

Role of Human Leukocyte Antigens (HLA) in Autoimmune Diseases

The aim of this review is to provide a brief overview of the role and current clinical relevance of HLA-B27 in spondyloarthritis and HLA-B51 in Behcet's disease as well as HLA-DQ2/DQ8 in celiac disease and HLA-DRB1 in rheumatoid arthritis and to discuss possible future implications.

Implications of the diversity of class I HLA associations in psoriatic arthritis

We sought to validate and extend the findings of a 282 psoriatic arthritis patient cohort from Dublin using a 219 patient cohort from Bath. The central finding of this study was that several structurally unrelated HLA alleles, including B*08:01:01, B*18:01:01, B*27:05:02, B*55:01:01 and C*06:02:01, were found to be significantly associated with particular phenotypic features of psoriatic arthritis, implying that the clinical diagnosis of psoriatic arthritis designates a genetically heterogeneous subset of individuals. Radiographic sacroiliitis was associated with either B*08:01:01, or B*27:05:02 with implications about the role of MHC molecules in an adaptive immune response. There are also implications for psoriatic arthritis diagnostic criteria since some disease features used in the criteria are under genetic control. These findings have important implications for understanding the role of MHC alleles in directing the adaptive immune response to mediate the inflammation responsible for psoriatic arthritis.

Review for Disease of the Year: Epidemiology of HLA-B27 Associated Ocular Disorders

Acute anterior uveitis is generally recognized as the most common form of uveitis. An association with HLA-B27 is seen in approximately half of cases of acute anterior uveitis. The prevalence of HLA-B27 varies widely between ethnic populations, with an approximate 8-10% prevalence in non-Hispanic whites and lower prevalence in Mexican- (4%) and African- (2-4%) Americans. A group of systemic inflammatory diseases, the spondyloarthropathies, similarly demonstrates a strong association with HLA-B27. The strength of association varies, depending on the specific spondyloarthropathy, with the strongest association found in patients with ankylosing spondylitis. The majority of patients with HLA-B27 associated uveitis will have an underlying spondyloarthropathy. Suspicion for HLA-B27 associated uveitis should prompt a careful clinical history to assess for features of a spondyloarthropathy as the characteristics of any associated uveitis may vary.

Autoinflammation and HLA-B27: Beyond Antigen Presentation

HLA-B27 associated disorders comprise a group of inflammatory conditions which have in common an association with the HLA class I molecule, HLA-B27. Given this association, these diseases are classically considered disorders of adaptive immunity. However, mounting data are challenging this assumption and confirming that innate immunity plays a more prominent role in pathogenesis than previously suspected. In this review, the concept of autoinflammation is discussed and evidence is presented from human and animal models to support a key role for innate immunity in HLA-B27 associated disorders.

Bone remodeling in psoriasis and psoriatic arthritis: an update

PURPOSE OF REVIEW

This article reviews and outlines recent advances in the field of bone remodeling in psoriatic disease and identify avenues for further research.

RECENT FINDINGS

High-resolution imaging revealed that new bone formation, observed in psoriatic arthritis (PsA) is centered at enthesial sites in contrast to hand osteoarthritis, and new bone formation is also present in psoriasis patients without arthritis. Accumulating evidence strongly suggests that the IL-23/IL-17 pathway is directly involved in altered bone phenotypes in PsA. Apart from Th17 and Th22 cells, CD8IL-17 T cells, γδT cells, and type 3 innate lymphoid cells also secrete IL-17 and IL-22. Further studies will be needed to clarify the role of these cells in bone remodeling in the context of psoriatic disease. Recent research also strengthened the earlier viewpoint that mechanical stress can serve as a trigger for joint inflammation and arthritis development. Recent findings suggest that inflammation beginning in the skin may become more generalized and involve musculoskeletal structures. Other reports suggest that gut microbiota might have a role in joint inflammatory responses and bone remodeling in psoriatic disease. Successful application of omics approaches and advance imaging studies also revealed many novel aspects of psoriatic diseases and joint-related pathologies which will likely help pinpoint causal genes, pathways, and novel biomarkers in the near future.

SUMMARY

Imaging studies have provided new insights into new bone formation phenotypes in PsA. The IL-23/IL-17 pathway is of central importance in psoriatic bone remodeling where, apart from CD4 T helper cells, other IL-17 and IL-22-secreting innate and adaptive cells may also be involved. Insights from study of the microbiome and from omics technologies will set the stage for new advances in our understanding of bone disorders in psoriatic diseases.

HLA-B27

Possession of the human leukocyte antigen (HLA) class I molecule B27 is strongly associated with ankylosing spondylitis (AS), but the pathogenic role of HLA-B27 is unknown. Two broad theories most likely explain the role of HLA-B27 in AS pathogenesis. The first is based on the natural immunological function of HLA-B27 of presenting antigenic peptides to cytotoxic T cells. Thus, HLA-B27-restricted immune responses to self-antigens, or arthritogenic peptides, might drive immunopathology. B27 can also "behave badly," misfolding during assembly and leading to endoplasmic reticulum stress and autophagy responses. β2m-free B27 heavy chain structures including homodimers (B272) can also be expressed at the cell surface following endosomal recycling of cell surface heterotrimers. Cell surface free heavy chains and B272 bind to innate immune receptors on T, NK, and myeloid cells with proinflammatory effects. This review describes the natural function of HLA-B27, its disease associations, and the current theories as to its pathogenic role.

HLA-B27 and psoriatic disease: a modern view of an old relationship

Psoriasis and PsA are the main phenotypes of psoriatic disease. Both conditions are highly polygenic diseases in which stochastic and environmental factors are crucial in the pathogenic process. Although the MHC region is a highly dense genetic area, most of the genetic basis of psoriatic disease within it resides in the HLA region. For decades, HLA-C*06 has been accepted as the main descriptor of the two main phenotypes of skin psoriasis. There is now compelling evidence to suggest that HLA-C*06 is only a genetic biomarker for skin involvement and not for joint involvement in psoriatic disease. The role of HLA-B*27 in the genetic aetiology of PsA has been recognized since the 1970s. Recent population case-control studies with adequate patient groups and replication cohorts, as well as confirmation studies in family pedigrees through the use of modern molecular typing methods, have reinforced the aetiological role of this allele in PsA. These studies have offered a new vision of the role of this allele in disease expression. This review contextualizes the latest findings on the role of HLA-B27 in psoriatic disease, emphasizing those aspects of particular interest for clinical practice.

Concepts of pathogenesis in psoriatic arthritis: genotype determines clinical phenotype

This review focuses on the genetic features of psoriatic arthritis (PsA) and their relationship to phenotypic heterogeneity in the disease, and addresses three questions: what do the recent studies on human leukocyte antigen (HLA) tell us about the genetic relationship between cutaneous psoriasis (PsO) and PsA – that is, is PsO a unitary phenotype; is PsA a genetically heterogeneous or homogeneous entity; and do the genetic factors implicated in determining susceptibility to PsA predict clinical phenotype? We first discuss the results from comparing the HLA typing of two PsO cohorts: one cohort providing the dermatologic perspective, consisting of patients with PsO without evidence of arthritic disease; and the second cohort providing the rheumatologic perspective, consisting of patients with PsA. We show that these two cohorts differ considerably in their predominant HLA alleles, indicating the heterogeneity of the overall PsO phenotype. Moreover, the genotype of patients in the PsA cohort was shown to be heterogeneous with significant elevations in the frequency of haplotypes containing HLA-B*08, HLA-C*06:02, HLA-B*27, HLA-B*38 and HLA-B*39. Because different genetic susceptibility genes imply different disease mechanisms, and possibly different clinical courses and therapeutic responses, we then review the evidence for a phenotypic difference among patients with PsA who have inherited different HLA alleles. We provide evidence that different alleles and, more importantly, different haplotypes implicated in determining PsA susceptibility are associated with different phenotypic characteristics that appear to be subphenotypes. The implication of these findings for the overall pathophysiologic mechanisms involved in PsA is discussed with specific reference to their bearing on the discussion of whether PsA is conceptualised as an autoimmune process or one that is based on entheseal responses.

Certain class I HLA alleles and haplotypes implicated in susceptibility play a role in determining specific features of the psoriatic arthritis phenotype

OBJECTIVES

Psoriatic arthritis (PsA) susceptibility is associated with several different class I alleles, suggesting separate patterns of MHC effect. This exploratory study was based on the hypothesis that heterogeneity of the clinical phenotype of PsA might be explained by differing associations of clinical features with these susceptibility genes.

METHODS

The clinical phenotype of 282 PsA patients in a cohort previously studied for associations with human leukocyte antigen (HLA)-B and HLA-C genotypes was first preliminarily assessed by univariate associations of susceptibility genes with specific clinical characteristics. To explore the potential genotypic effects of pairwise combinations of different HLA-B and C alleles/haplotypes, we created a series of allele/haplotype risk scores combining single alleles/haplotypes separately associated with being in the highest PsA severity propensity tertile based on the features studied by univariate analysis.

RESULTS

In exploratory univariate analyses, B*27:05:02 was positively associated with enthesitis, dactylitis and symmetric sacroiliitis, whereas B*08:01:01-C*07:01:01and its component alleles were positively associated with joint fusion and deformities, asymmetrical sacroiliitis, and dactylitis. HLA-C*06:02:01 was negatively associated with asymmetrical sacroiliitis. The highest propensity score for severe PsA was with B*27:05:02-C*02:02:02, B*08:01:01-C*07:01:01 and B*37:01:01-C*06:02:01, but not the B*27:05:02-C*01:01:01 or B*57:01:01-C*06:02:01 haplotypes. In contrast, B*44 haplotypes were associated with presence of milder disease, and in univariate analysis with a decreased frequency of enthesitis, joint fusion, deformities and dactylitis.

CONCLUSIONS

Different HLA susceptibility genes were associated with particular features that defined the PsA phenotype of a given patient. Additive interactions between different susceptibility HLA alleles defined the propensity for a more severe or milder musculoskeletal phenotype.

Polymorphism of HLA-B27: 105 subtypes currently known

HLA-B27 has a high degree of genetic polymorphism, with 105 known subtypes, named HLA-B*27:01 to HLA-B*27:106, encoded by 132 alleles. The most common subtypes associated with ankylosing spondylitis are HLA-B*27:05 (Caucasians), HLA-B*27:04 (Chinese), and HLA-B*27:02 (Mediterranean populations). For Chinese populations, HLA-B*27:04 is associated with a greater ankylosing spondylitis risk than HLA-B*27:05. Two subtypes, HLA-B27*06 and HLA-B27*09, seem to have no disease association. These differential disease associations of HLA-B27 subtypes, and the recent discovery that ERAP1 is associated with ankylosing spondylitis for patients with HLA-B27, have increased attempts to determine the function of HLA-B27 in disease pathogenesis by studying hemodynamic features of its protein structure, alterations of its peptidome, aberrant peptide handling, and associated molecular events. However, after 40 years we still do not fully know how HLA-B27 predisposes to ankylosing spondylitis and related spondyloarthritis.

The link between HLA-B27 and SpA--new ideas on an old problem

The strong association of the HLA-B27 with AS was first discovered independently by groups in London and California in 1972 and has recently been confirmed beyond reasonable doubt by fine mapping in the latest and most sophisticated genome-wide association study (GWAS) published this July. Yet, despite nearly four decades of extensive research, the exact role that HLA-B27 plays in pathogenesis remains unknown. However, we believe that recent developments in three fields have allowed us to view this conundrum in a new light and to propose coherent theories of disease pathogenesis. These areas are as follows: (i) GWASs, (ii) studies of B27 biology and (iii) lessons from biologic therapies. In this review we will discuss these recent advances before discussing the current models of AS pathogenesis under investigation.

HLA associations reveal genetic heterogeneity in psoriatic arthritis and in the psoriasis phenotype

OBJECTIVE

Rigorously ascertained cases of psoriatic arthritis in subjects presenting to a rheumatology unit were compared with cases of psoriasis in subjects presenting to a dermatology unit, where subjects with musculoskeletal features were excluded, to address 1) the extent to which the contribution of the major histocompatibility complex (MHC) to psoriatic arthritis susceptibility resembles that in psoriasis, and 2) whether MHC genes determine quantitative traits within the psoriatic arthritis phenotype.

METHODS

Separate discovery and validation subcohorts of patients recruited from a relatively homogeneous population were studied by sequence-based HLA typing, in which frequencies of the HLA-B and HLA-C alleles and haplotypes were compared.

RESULTS

In patients with psoriatic arthritis, the frequency of C*06:02 was lower than that in patients with psoriasis (28.7% versus 57.5%; P = 9.9 × 10(-12) ). Three haplotypes containing B*27:05 or B*39:01 were significantly increased in frequency in patients with psoriatic arthritis, but not in those with psoriasis. The structurally related B*39:06 allele was not increased in frequency. B*27 was associated with an interval of 0.98 years between skin and musculoskeletal disease (P = 2.05 × 10(-6) ), compared with an interval of 10.14 years for C*06. Preliminary evidence suggested that B*38:01 and B*08 may be associated with psoriatic arthritis susceptibility, and that allotypes encoding P2 pockets that bind side chains opposite in charge from those encoded by the B*27 and B*39 molecules may exert a protective role.

CONCLUSION

These findings suggest that the psoriasis phenotype results from two patterns of MHC effect. The first involves the classic psoriasis susceptibility gene C*06, which confers more penetrant skin disease with less prevalent and more time-dependent musculoskeletal phenotype development. The second pattern appears to be mediated by HLA-B alleles, notably B*27, and includes temporally more coincident musculoskeletal involvement that is nearly equivalent in penetrance to that of the skin disease.

Seronegative spondyloarthritis

Seronegative spondyloarthritis (SpA) is a group of inflammatory rheumatic diseases with common clinical and aetiological features, including axial and peripheral inflammatory arthritis, enthesitis, extra-articular manifestations and a close link to the presence of the human leucocyte antigen (HLA)-B27 epitope. Ankylosing spondylitis is the most common of the SpA diseases, with prevalence in the Caucasian population ranging between 0.15% and 1.8%, generally higher in populations with a higher background prevalence of HLA-B27 positivity. Incidence has been estimated between 0.49 (Japan) and 10 (Norway) per 100,000. The prevalence of psoriatic arthritis ranges from 0.02% to 0.2%, and the incidence in the normal population is 7.2 per 100,000 per year. In patients with existing psoriasis, the prevalence of psoriatic arthritis rises to 6-42%. The prevalence of reactive arthritis is dependent on the background incidence of gastrointestinal or genitourinary infections; incidence has been described as up to 30-40 per 100,000. SpA symptoms are present in up to 50% of patients with inflammatory bowel disease.

Enteropathic spondyloarthropathy: A common genetic background with inflammatory bowel disease?

The association between spondyloarthropathy and inflammatory bowel disease (IBD) is largely established, although prevalence is variable because of different population selection and diagnostic methodologies. Most studies indicate that as many as 10%-15% of cases of IBD are complicated by ankylosing spondylitis (AS) or other forms of spondylarthritis (SpA). Of note, ileal inflammation resembling IBD has been reported in up to two thirds of cases of SpA, and it has been suggested that the presence of ileitis is associated with the chronicity of articular complications. Although this observation is of interest to unravel the pathophysiology of the disease, systematic screening of patients with SpA by ileocolonoscopy is not indicated in the absence of gut symptoms, as only a small proportion of patients with subclinical gut inflammation will develop overt IBD over time. The existence of familial clustering of both IBD and AS, the coexistence of both conditions in a patient, the evidence of an increased risk ratio among first- and second-degree relatives of affected AS or IBD patients and finally, the increased cross-risk ratios between AS and IBD, strongly suggest a shared genetic background. So far, however, IL23R is the only identified susceptibility gene shared by both IBD and AS. Although functional studies are still needed to better understand its pathogenic role, great effort is being spent therapeutically targeting this pathway that may prove effective for both disorders.

The prevalence, clinical features and association of HLA-B27 in sacroiliitis associated with established Crohn's disease

BACKGROUND

Sacroiliitis is a recognized complication of Crohn's disease and may occur distinct from progressive ankylosing spondylitis (AS).

AIM

To estimate prospectively the prevalence of sacroiliitis in patients with established Crohn's disease, to characterize the clinical features and to correlate these with the presence of HLA-B27.

METHODS

All Crohn's disease patients under active follow-up of between 5 and 12 years duration were invited to participate. Patients underwent a clinical evaluation including symptom questionnaire, rheumatological examination and underwent HLA genotyping. Patients then underwent magnetic resonance imaging (MRI) of the sacroiliac joints. The clinical and radiological factors were correlated with HLA-B27 status.

RESULTS

56 patients underwent initial assessment and 44 had MRI scans. Seventeen of 44 (39%) patients had MRI evidence of sacroiliitis, of whom 5 fulfilled the criteria for AS. Symptoms of low back pain were elicited in a majority of these patients--11/17 (65%) compared to 3 of 27 (11%) patients with normal scans (P = 0.003). There were no differences in functional indices with the exception of patients with AS. HLA-B27 was present in seven patients, and all seven had MRI evidence of sacroiliitis, five had AS.

CONCLUSIONS

Sacroiliitis is common in patients with established Crohn's disease and in the majority of cases, patients have symptoms of inflammatory low back pain if questioned carefully. HLA-B27 is not associated with isolated sacroiliitis, but is associated with AS. However, possession of HLA-B27 appears to convey a very high risk of developing axial inflammation in Crohn's disease.

Early psoriatic arthritis

In the majority of patients with psoriatic arthritis (PsA), it is a chronic progressive disease, and only 12% of patients with early PsA will be in disease-modifying antirheumatic drug-free remission at 2 years. Radiologic damage occurs in the early stages of PsA; up to 47% of patients with PsA have radiologic erosions after 2 years. This article reviews the clinical features of early PsA, pathologic insights into PsA gleaned from studies of early PsA, and the current state of diagnostic imaging and therapeutics in early PsA.

Psoriatic patients with arthropathy show significant expression of free HLA class I heavy chains on circulating monocytes: a potential role in the pathogenesis of psoriatic arthropathy

BACKGROUND

Surface free heavy chains on monocytes were recently implicated in playing a role in the pathogenesis of several forms of arthritis.

OBJECTIVES

To determine the expression of surface free heavy chains (recognized by monoclonal antibody HC10) on peripheral blood mononuclear cells of psoriatic patients with or without arthropathy.

METHODS

Twenty-eight psoriatic patients from the dermatology outpatient clinic were included in this study. Blood samples were collected during outpatient visits and clinical characteristics of the patients were documented. Quantitative analyses of circulating mononuclear cells were performed using flow cytometry.

RESULTS

Circulating monocytes showed higher expression of HC10 compared with circulating lymphocytes (P < 0.05). Psoriatic patients with arthropathy showed elevated expression of HC10 on peripheral blood monocytes compared with those without arthropathy (P < 0.05). Among the arthropathic group, those without the human leucocyte antigen (HLA)-B27 allele showed even higher expression of HC10 on circulating monocytes compared with those possessing HLA-B27 (P < 0.05). The polyarthropathic subgroup showed the highest HC10 expression, but the level of expression was not high enough to be of statistical significance compared with other arthropathic subgroups. No correlation was found between psoriatic skin involvement and the expression of HC10 on circulating monocytes.

CONCLUSIONS

The presence of free heavy chains on circulating monocytes is closely associated with psoriatic arthropathy, while the expression of free heavy chains on circulating monocytes has no significant influence on psoriatic skin lesions.

Discovery: HLA and disease

This article is a personal account of the author's involvement in the discovery of HLA associations with ankylosing spondylitis; Reiter disease; acute anterior uveitis; and the arthropathies associated with psoriasis, chronic inflammatory bowel disease, and sarcoidosis.

Frequency of extraintestinal manifestations in patients with inflammatory bowel disease in Northwest Greece and review of the literature

BACKGROUND

Inflammatory bowel disease mainly affects the bowel but also has extraintestinal manifestations.

AIMS

To report the frequency of extraintestinal manifestations in patients with inflammatory bowel disease in Northwest Greece. PATIENTS; The data files of 256 inflammatory bowel disease patients (diagnosis between 1983-19971 were analysed.

METHODS

Retrospective investigation of patient files.

RESULTS

In patients with ulcerative colitis: 13.9% (30/215) had developed skin manifestations, 6% (13/215) had kidney stones, 1.39% (3/215) had iridocyclitis, 1.86% (4/215) had primary sclerosing cholangitis, 4.18% (9/215) had sacroiliitis, 8.31% (18/215) had peripheral arthalgias, 2.3% (5/215) had colitic arthritis and finally 1.39% (3/215) had deep vein thrombosis). In patients with Crohn's disease: 24.3% (9/37) had developed skin manifestations, 5.4% (2/37) had kidney stones, 2.7% (1/37) had iridocyclitis, 16.2% (6/37) had sacroiliitis, 8.1% (3/37) had peripheral arthralgias, 5.4% (2/37) had colitic arthritis and, finally, 8.1% (3/37) had deep vein thrombosis. Sacroiliitis (p = 0.01), deep vein thrombosis (p = 0.04) and erythmema nodosum (p = 0.01) were more common in patients with Crohn's disease.

CONCLUSIONS

Extraintestinal manifestations are not rare in patients with inflammatory bowel disease, especially in Crohn's disease patients, in our area, but have, generally, a mild profile.

HLA-B27 transgenic rats are susceptible to accelerated alveolar bone loss

BACKGROUND

HLA-B27 transgenic rats exhibit generalized, severe inflammatory reactions and spontaneously develop arthritis and chronic gastrointestinal inflammation, as well as inflammatory lesions in other tissues. Our hypothesis was that HLA-B27 rats would also be susceptible to inflammatory periodontal disease, and therefore alveolar bone loss. The purpose of this investigation was to compare the naturally occurring alveolar bone loss in HLA-B27 and wild type rats.

METHODS

Age- and sex-matched HLA-B27 transgenic (TG) and wild type Fischer 344 (WT) female retired breeders, and their age-matched male WT breeding mates, were examined for alveolar bone loss (ABL). Thirty-eight animals were used: twelve, 20, and 6 animals were 6, 8, and 12 months old, respectively. ABL was measured as the exposed root surface area (mm2) in the defleshed maxilla and mandible.

RESULTS

The coefficient of variation for replicate ABL measurements was 4.4%. For the 6- and 8-month age groups, ABL was significantly greater in TG rats compared to WT rats. The observed difference in ABL between TG and WT animals did not reach statistical significance for the 12-month age group. Within each of the two animal groups (TG and WT), ABL was significantly different between age groups. The ABL rate of TG female rats was 42% to 250% greater than that of WT female rats, depending on the age range examined.

CONCLUSIONS

HLA-B27 rats are susceptible to accelerated alveolar bone loss and could serve as an animal model of alveolar bone loss pathogenesis.

Insights into the pathogenesis of psoriasis and psoriatic arthritis

Psoriasis and its related arthritis are chronic inflammatory disorders affecting predominantly the skin and synovium. Although their etiology remains to be established, multiple factors seem to play important roles in their pathogenesis. These environmental (eg, infectious agents and trauma), genetic, and immunologic factors are reviewed in this article.

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.

Review article: Pathophysiology of the intestinal mucosa in inflammatory bowel disease and arthritis: similarities and dissimilarities in clinical findings

Although apparently dissimilar in both structure and function, the gut and locomotor system are linked by a number of clinical syndromes in which both are involved. In inflammatory bowel disease, intestinal mucosal inflammation is the primary problem, but may be associated with both axial and peripheral arthropathies. In the seronegative spondyloarthropathies the primary problem is in the locomotor system, but intestinal abnormalities may also be present. In addition, non-steroidal anti-inflammatory drugs used in their treatment, may cause a distinct enteropathy which may be confused with the disease-related intestinal abnormalities. The clinical, histological and genetic features of these conditions are examined in order to assess their relationship and the central role of the intestinal mucosa in their pathogenesis.

Psoriatic arthritis. Historical background and epidemiology

Psoriatic arthritis was first described in the early part of the nineteenth century. Over the past 50 years, concepts of the disease have evolved as a result of clinical, epidemiological, radiological and immunogenetic study. Epidemiological and clinical investigations suggest that the disease is a unique arthropathy rather than the coincident occurrence of two common diseases. There are no validated criteria for classification; this is partly because of the heterogeneous clinical features associated with the disease, and the relapsing and remitting nature of both psoriasis and arthritis. Clinical subgroups have been proposed and have proved useful in study of the disease; however, there are inconsistencies and overlaps in the published data. The population prevalence of psoriatic arthritis is in the range of 2-10 per 10,000 although this is probably an underestimate as those with sacroiliac involvement only are not included. There are currently no incidence figures from population samples. The disease is slightly more common in females than males, although there is variation in the sex ratio by disease subgroup. There is evidence that hormonal and environmental factors play a role in the occurrence of disease.

The place of psoriatic arthritis in the spondarthritides

The place of psoriatic arthritis in the spondarthritides has been examined in terms of past, present and future aspects. It is concluded that: 1. PsA is a definite entity and separate from rheumatoid arthritis. 2. The spondarthritis concept is universally accepted, although still in an evolving stage. 3. A more definitive picture of the spondarthritides and of PsA itself could arise from a number of new approaches, some entirely novel, some extensions of work already in progress. Avenues of future research that are likely to be fruitful include those involving: more refined clinical studies; further applications of molecular mapping; and, common to both, conceptual advances using mathematical models to provide a more 'three-dimensional' picture.