Histocompatibility alloantigens in psoriasis and psoriatic arthritis. Evidence for the influence of multiple genes in the major histocompatibility complex

Genetic markers for psoriatic arthritis among patients with psoriasis. Part II: HLA genes

Psoriatic arthritis often leads to the development of severe outcomes ankylosis, deformities of the affected joints with severe impairment of their functions and disability. Early identification of patients with psoriasis with an increased risk of developing psoriatic arthritis for the purpose of its timely diagnosis and early initiation of therapy can prevent the development of severe disease outcomes. It is believed that the genes of the HLA system make the greatest individual genetic contribution to the formation of a predisposition to hereditary diseases with polygenic inheritance. The literature review considers the polymorphisms of the genes of the HLA system, associated with the development of psoriatic arthritis, in patients with psoriasis. The HLA alleles that contribute to the development of psoriatic arthritis and its individual forms have been identified. HLA alleles have been identified, which have a protective effect against the development of psoriatic arthritis.

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.

Association of HLA Alleles and HLA Haplotypes with Psoriasis, Psoriatic Arthritis and Disease Severity in a Miscegenated Population

Background

The study of HLA classes I and II in Brazilian psoriasis patients may contribute to a better understanding of their association with the disease.

Objective

To describe HLA classes I and II of Brazilian patients with psoriasis, with or without arthritis, compare them to controls and correlate HLA markers with epidemiological and evolutional aspects of psoriasis.

Methods

A total of 55 patients with more than 5 years of psoriasis, with or without arthritis, answered a questionnaire on ethnic background and disease severity. A total of 134 bone marrow donors were controls. HLA class I and II genotyping was determined by PCR-SSP.

Results

Mean age was 42.4 years; 23 women and 32 men. HLA-B*57 was present in 23.6% patients and in 7.5% controls (p=0.00200, OR= 3.8381), and HLA-C*06 in 29.1% patients and in 16.4% controls (p= 0.04832, OR=2.0886). HLA-B*57 and HLA-C*18 were significantly present in patients with arthritis (p=0.00104, OR=6.6769 and p=0.00269, OR=16.50, respectively). HLA-B*57 was significantly present in patients with history of erythroderma (p=0.00548, OR= 5.1059), as was HLA-C*06 (p=0.02158, OR=3.0545). HLA-B*57 was also frequent in patients with history of hospital internment due to psoriasis (p= 0.00094, OR=7.8909) and in the ones with history of systemic treatment for psoriasis (p= 0.00011, OR= 5.3733). Haplotype HLA-A*02 B*57 C*06 DRB1*07DQB1*03 was the most common among the patients (p= 0.00069, OR= 3.528).

Conclusion

HLA-B*57 and HLA-C*06 were significantly increased in the patients indicating risk for psoriasis. HLA-B*57 remained high in patients with history of erythroderma, hospital internment, systemic treatment, and psoriatic arthritis, showing association with disease severity. HLA-C*18 was significantly high only in patients with psoriatic arthritis. HLA-B*57 and HLA-C*06 and haplotype HLA-A*02B*57Cw*06DRB1*07 DQB1*03 seen in this study were already described before, associated with psoriasis. HLA-Cw*18 was not described in other populations in association with psoriasis.

Associations between human leukocyte antigen C locus polymorphism and psoriatic arthritis in populations of European and Middle Eastern descent: a meta-analysis

BACKGROUND

Gene-disease association between human leukocyte antigen (HLA)-C locus polymorphism and psoriatic arthritis (PsA) remains controversial.

OBJECTIVE

Evaluate the relationship between HLA-C locus polymorphism and PsA in populations of European and Middle Eastern descent.

SEARCH METHODS

PubMed, PMC, Elsevier and Google Scholar databases from 1980 to January 2020. The search was limited to articles in English.

SELECTION CRITERIA

Case-control studies (with unrelated participants) that had allele/genotype data on the association between HLA-C locus polymorphism and PsA susceptibility.

DATA COLLECTION AND ANALYSIS

Two investigators searched independently in searching the literature. Disagreements were resolved by discussion and consultation with a third researcher. The Q-Genie tool was used to assess the quality of articles.

RESULTS

Twenty-five studies met the inclusion criteria. At the allelic level, three alleles were associated with an increased risk of PsA and five were associated with a reduced risk. At the phenotypic level, four alleles were associated with increased risk of PsA and three were associated with a reduced risk. At both the allelic and phenotypic levels, the results revealed that HLA-C*04 played a protective role in PsA (The pooled odds ratio [OR] is 0.66 for allelic level and 0.63 for phenotypic level), while HLA-C*02, *06 and *12 increased the risk of suffering from PsA (The pooled ORs of C*02, *06 and *12 are 2.21, 2.63 and 1.49 for allelic level, and 1.79, 2.96 and 2.25 for phenotypic level, respectively).

CONCLUSION

The pooled results showed a significant association between PsA and the HLA-C gene in populations of European and Middle Eastern descent. At both the allelic and phenotypic levels, the HLA-C*02, *06 and *12 may contribute to susceptibility to PsA, while HLA-C*04 may confer a protective role against PsA.

REGISTRATION

Not registered.

CONFLICT OF INTEREST

None.

Complexities in Genetics of Psoriatic Arthritis

PURPOSE OF THE REVIEW

To provide a general overview and current challenges regarding the genetics of psoriatic disease. With the use of integrative medicine, multiple candidate loci identified to date in psoriatic disease will be annotated, summarized, and visualized. Recent studies reporting differences in genetic architecture between psoriatic arthritis and cutaneous-only psoriasis will be highlighted.

RECENT FINDINGS

Focusing on functional pathways that connect previously identified genetic variants can increase our understanding of psoriatic diseases. The genetic architecture differs between psoriatic arthritis and cutaneous-only psoriasis with arthritis-specific signals in linkage disequilibrium independent of the published psoriasis signals. Integrative medicine is helpful in understanding cellular mechanisms of psoriatic diseases. Careful selection of the psoriatic disease cohort has translated into mechanistic differences among psoriatic arthritis and cutaneous psoriasis.

Human leukocyte antigen and demographic characteristics in Chinese patients with active peripheral type psoriatic arthritis who had inadequate response to conventional disease-modifying antirheumatic drugs in a single dermatologic clinic

Background

Correlation between severity of psoriasis and psoriatic arthritis (PsA) is inconsistent. Also, human leukocyte antigen (HLA)-Cw6 was found to be underrepresented in severe psoriasis who failed conventional systemic therapies, but the effect of HLA polymorphism on PsA severity needs to be confirmed.

Objectives

To describe the severity of psoriasis, demographic features and HLA polymorphism among Chinese patients with active peripheral type PsA who had inadequate response to conventional disease-modifying antirheumatic drugs.

Methods

We included all patients with PsA who had at least 3 tender and swollen peripheral joints despite at least two conventional non-biologic treatments in our clinic. Demographic results were compared with global pivotal studies of biologics for PsA. HLA-Cw and HLA-DRB1 genotyping was also analyzed.

Results

We identified 60 patients who met our inclusion criteria. The male to female ratio was 1.31:1. The majority of patients presented with psoriasis first (81.7%). The mean interval between psoriasis and PsA was 7.2 ± 8.1 years (mean ± SD). The baseline number of tender and swollen joints was 14.9 ± 10.7 and 11.3 ±10.2, respectively. In total, 41.7% subjects had more than 3% body surface area involvement of psoriasis. Genotyping of HLA-Cw and HLA-DRB1 was performed in 47 subjects. HLA-Cw*0702 was the most frequent allele (29.8%), followed by HLA-Cw*01 (26.6%). The frequency of HLA-Cw*0602 allele was similar to normal population. The most frequent HLA-DRB1 allele was HLA-DRB1*04 (20.2%), followed by HLA-DRB1*08 (16.0%). No cases carrying HLA-DRB1*13 were detected.

Conclusions

Compared with Western population, our patients had less psoriasis and PsA burden. The frequencies of HLA-Cw*06, HLA-Cw*12, and HLA-DRB1*07 were not increased. In contrast, HLA-Cw*0702 and HLA-DRB1*08 allele frequencies were increased compared with psoriasis patients and normal population in Taiwan. Future studies are still needed to characterize the demographic and genetic features of high need PsA patients.

HLA-Cw6 and psoriasis

Psoriasis is a multifactorial disease with a strong genetic background. HLA-Cw6 is one of the most strongly associated psoriasis susceptibility alleles. It is repeatedly observed to affect disease course, phenotypic features, severity, comorbidities and treatment outcomes. To the best of our knowledge, the roles of HLA-Cw6 in psoriasis have not yet been thoroughly reviewed. The worldwide frequency of the HLA-Cw6 allele varies greatly, with it being generally higher in white people than in Asians. The allele is associated with type I early-onset psoriasis. Stress, obesity and streptococcal pharyngitis are commonly observed in HLA-Cw6-positive patients. Phenotypically, HLA-Cw6 has been found to be associated with guttate psoriasis. In addition, patients carrying the allele are more likely to have arm, leg and trunk involvement, and the Koebner phenomenon. Patients with psoriatic arthritis with HLA-Cw6 more often have early onset and tend to show cutaneous symptoms before musculoskeletal symptoms. HLA-Cw6-positive patients have been shown in several studies to be more responsive to methotrexate and ustekinumab. However, this difference in ustekinumab efficacy was only moderate in a post-hoc analysis of a pivotal phase III study. HLA-Cw6 positivity also tends to be less frequent in high-need patients who fail conventional therapy. Small studies have also investigated the role of HLA-Cw6 in remission of psoriasis during pregnancy, and with the comorbidities of photosensitivity and atherosclerosis. Given the diverse nature of psoriasis pathogenesis, as well as the difference of HLA-Cw6 positivity in different ethnic groups, more studies are needed to confirm the role of HLA-Cw6 in psoriasis.

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.

Clinical and immunogenetic characterization in psoriatic arthritis patients

In psoriatic arthritis (PsA), genetic factors play a substantial role in disease susceptibility as well as in its expression. This study aims to determine the distribution of class I and class II HLA antigens in PsA patients and secondly to analyze the influence of genetic factors in the clinical expression of the disease. Consecutive PsA patients (CASPAR criteria) with less than 1 year of disease duration were included. Sociodemographic and clinical data were recorded. Blood samples were obtained, DNA was extracted by polymerase chain reaction (PCR), and class I (A, B, and C) and class II (DR) HLA antigens were determined by oligotyping. A control group of 100 nonrelated healthy controls from the general population served as control. p values were corrected (pc) according to the number of alleles tested. A total of 73 patients were included, 37 were females (50.7 %) with a median disease duration of 72 months (interquartile range (IQR) 24-149). Thirty-three patients (45.2 %) had a family history of psoriasis. When analyzing all the class I and class II HLA antigens, a significantly higher frequency of B38 (odds ratio (OR) 2.95, p = 0.03) and Cw6 (OR 2.78, p = 0.009) was found in PsA patients compared to the control group. On the contrary, the HLA-A11 (OR 0.14, p = 0.04) and B7 (OR 0.31, p = 0.03) were significantly more frequent among healthy controls. Furthermore, B18 was significantly more frequent in patients with early arthritis onset (less than 40 years): seven patients (22.6 %) with early onset compared to two patients (4.8 %) with late onset (p = 0.03). No association between HLA-B27 and spondylitis or HLA-DR4 with polyarticular involvement was observed. The HLA-B38 and Cw6 alleles are associated with a greater PsA susceptibility in Argentine population.

Behçet's disease in HLA-B*51 negative Germans and Turks shows association with HLA-Bw4-80I

Introduction

Behçet’s disease (BD) as systemic vasculitis of unknown etiology is associated with HLA-B*51 in European and Asian populations. HLA-A*26 was claimed as an additional BD susceptibility marker in Japanese and Greek patients. This study was performed to test for HLA associations in HLA-B*51 negative German and Turkish BD populations.

Methods

In total, 65 German and 46 Turkish patients lacking HLA-B*51 were analyzed in comparison to healthy HLA-B*51 negative Germans (n = 1500) and Turks (n = 130). HLA-A/B genotypes were determined by SSOP. P-values with correction for multiple testing (p_c), χ2-test and odds ratio (OR) were used for statistical evaluation.

Results

HLA-A*26 was significantly more frequent in HLA-B*51⁻ German patients [p_c = 0.0076, OR = 3.23, 95% CI 1.63 to 6.39] than in respective controls. HLA-A*26 was also elevated in a smaller group of Turkish patients versus the controls. Significant association of HLA-Bw4 with isoleucine at amino-acid position 80 (HLA-Bw4-80I) was found in the HLA-B*51⁻ German cohort of BD patients [p_c = 0.0042, OR = 2.35, 95% CI 1.41 to 3.93) and in the Turkish patients in comparison to the respective controls [p = 0.025, OR = 2.17, 95% CI 1.09 to 4.31]. On the contrary, HLA-Bw4-80 T was reduced in both HLA-B*51⁻ BD patient cohorts.

Conclusions

The study shows a significant association of HLA-Bw4-80I present on HLA-B*51 as well as on other B-locus molecules with BD. This indicates that distinctive Bw4 epitopes on HLA-B locus molecules could play a role in BD pathogenesis. The study also indicates an association with HLA-A*26 in German and Turkish BD patients as a genetic risk factor independent of HLA-B*51.

Interleukin 4 as a potential drug candidate for psoriasis

BACKGROUND

Interleukin 4 (IL-4) is the central cytokine driving the differentiation of naive CD4(+) T helper (TH) cells into anti-inflammatory IL-4-producing TH2 cells. In contrast, IL-12/IL-23 promotes the development of TH1/TH17 immune responses that induce organ-specific autoimmune diseases such as psoriasis or multiple sclerosis.

OBJECTIVE

We focus on the potential of IL-4 and TH2 induction to treat inflammatory autoimmune diseases.

METHODS

Here, we summarize the basics for the establishment of the in vitro and in vivo conditions for the generation of TH2 immune responses, followed by various experimental data showing the therapeutic use of IL-4 for the therapy of autoimmune diseases. This data and early experiences with recombinant human IL-4 (rhIL-4) in the therapy of patients with cancer set the basis for the clinical introduction of rhIL-4 in the treatment of patients with psoriasis in a Phase I/II trial.

CONCLUSION

IL-4 seems to act by inducing an anti-inflammatory phenotype and further clinical trials will explore the promising therapeutic potency of IL-4 in psoriasis during the upcoming era of biologics.

Genetics of spondyloarthritis--beyond the MHC

Ankylosing spondylitis (AS), psoriasis and inflammatory bowel disease (IBD) often coexist in the same patient and in their families. In AS, genes within the MHC region, in particular HLA-B27, account for nearly 25% of disease hereditability, with additional small contributions from genes outside of the MHC locus, including those involved in intracellular antigen processing (that is, ERAP1, which interacts with HLA-B27) and cytokine genes such as those involved in the IL-17-IL-23 pathway. Similar to AS, the strongest genetic signal of susceptibility to psoriasis and psoriatic arthritis also emanates from the MHC region (attributable mostly to HLA-C(*)06:02 although other genes have been implicated), and gene-gene interaction of HLA-C with ERAP1. The remaining hereditary load is from genes involved in cytokine production, specifically genes in the IL-17-IL-23 pathway, the NFκB pathway and the type 2 T-helper pathway. In IBD, similar genetic influences are operative. Indeed, genes important in the regulation of the IL-17-IL-23 pathway and, in Crohn's disease, genes important for autophagy (that is, NOD2 and ATG16L1 and IRGM) have a role in conferring susceptibility of individuals to these diseases. Thus, AS, psoriasis and IBD seem to share similar pathogenic mechanisms of aberrant intracellular antigen processing or elimination of intracellular bacteria and cytokine production, especially in the IL-17-IL-23 pathway.

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.

Comparison of MHC class I risk haplotypes in Thai and Caucasian psoriatics shows locus heterogeneity at PSORS1

Earlier studies have shown that psoriasis in Japan and Thailand is associated with two different major histocompatibility complex (MHC) haplotypes - those bearing HLA-Cw6 and those bearing HLA-Cw1 and HLA-B46. In an independent case-control sample from Thailand, we confirmed the association of psoriasis with both haplotypes. No association was seen in Thai HLA-Cw1 haplotypes lacking HLA-B46, nor was HLA-Cw1 associated with psoriasis in a large Caucasian sample. To assess whether these risk haplotypes share a common origin, we sequenced genomic DNA from a Thai HLA-Cw1-B46 homozygote across the ∼300 kb MHC risk interval, and compared it with sequence of a HLA-Cw6-B57 risk haplotype. Three small regions of homology were found, but these regions share equivalent sequence similarity with one or more clearly non-risk haplotypes, and they contain no polymorphism alleles unique to all risk haplotypes. Differences in psoriasis phenotype were also observed, including lower risk of disease, greater nail involvement, and later age at onset in HLA-Cw1-B46 carriers compared with HLA-Cw6 carriers. These findings suggest locus heterogeneity at PSORS1 (psoriasis susceptibility 1), the major psoriasis susceptibility locus in the MHC, with HLA-Cw6 imparting risk in both Caucasians and Asians, and an allele other than HLA-Cw1 on the HLA-Cw1-B46 haplotype acting as an additional risk variant in East Asians.

Psoriasis vulgaris and human leukocyte antigens

BACKGROUND

Psoriasis vulgaris is a skin disease with a complex immunological and genetic background, triggered by environmental factors. The association of human leukocyte antigens (HLA) and psoriasis has long been reported on population and familial studies.

OBJECTIVES

To review and discuss studies on psoriasis vulgaris and HLA, in Caucasian and non-Caucasian populations.

METHODS

The major population studies on psoriasis vulgaris and the associated HLA antigens and alleles are described and discussed based on a review of the current literature.

RESULTS

Population studies demonstrate the presence of different HLA specificities as well as extended haplotypes in patients with psoriasis, when compared to controls. Some alleles occur in a lower frequency in patients with psoriasis, indicating they could be protection alleles. In all studies which HLA class I was typed, Cw6 or Cw*0602 was present in a significant frequency in patients with psoriasis, mainly when early onset and positive family history were considered. HLA-DRB1*0701 was also present in a higher frequency in patients in different populations.

CONCLUSIONS

Different antigens and alleles from both HLA classes I and II were seen in a significantly higher frequency in patients with psoriasis vulgaris. HLA Cw*0602 and DRB1*0701 were represented in different reports, and the former was related mainly to psoriasis type I.

Sequence and haplotype analysis supports HLA-C as the psoriasis susceptibility 1 gene

Previous studies have narrowed the interval containing PSORS1, the psoriasis-susceptibility locus in the major histocompatibility complex (MHC), to an approximately 300-kb region containing HLA-C and at least 10 other genes. In an effort to identify the PSORS1 gene, we cloned and completely sequenced this region from both chromosomes of five individuals. Two of the sequenced haplotypes were associated with psoriasis (risk), and the other eight were clearly unassociated (nonrisk). Comparison of sequence of the two risk haplotypes identified a 298-kb region of homology, extending from just telomeric of HLA-B to the HCG22 gene, which was flanked by clearly nonhomologous regions. Similar haplotypes cloned from unrelated individuals had nearly identical sequence. Combinatorial analysis of exonic variations in the known genes of the candidate interval revealed that HCG27, PSORS1C3, OTF3, TCF19, HCR, STG, and HCG22 bore no alleles unique to risk haplotypes among the 10 sequenced haplotypes. SPR1 and SEEK1 both had messenger RNA alleles specific to risk haplotypes, but only HLA-C and CDSN yielded protein alleles unique to risk. The risk alleles of HLA-C and CDSN (HLA-Cw6 and CDSN*TTC) were genotyped in 678 families with early-onset psoriasis; 620 of these families were also typed for 34 microsatellite markers spanning the PSORS1 interval. Recombinant haplotypes retaining HLA-Cw6 but lacking CDSN*TTC were significantly associated with psoriasis, whereas recombinants retaining CDSN*TTC but lacking HLA-Cw6 were not associated, despite good statistical power. By grouping recombinants with similar breakpoints, the most telomeric quarter of the 298-kb candidate interval could be excluded with high confidence. These results strongly suggest that HLA-Cw6 is the PSORS1 risk allele that confers susceptibility to early-onset psoriasis.

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.

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.

Lack of evidence for genetic association to RUNX1 binding site at PSORS2 in different German psoriasis cohorts

A DNA variant, rs734232, altering a RUNX1 binding site was recently reported as susceptibility allele at PSORS2 (17q25) in cohorts of psoriasis patients from the US. A testing of this variant in psoriasis patients from Germany did not confirm this association in 300 trios nor in two case-control studies with 281 patients with psoriasis vulgaris and 375 patients with psoriatic arthritis, respectively. These results fail to support rs734232 as a psoriasis susceptibility factor in German psoriasis patients.

The genetic basis of spondyloarthritis

Spondyloarthritis tends to cluster in families and, to a great extent, is associated with human leukocyte antigen (HLA) B27. In fact, the population frequency of spondyloarthritis in most groups is proportional to that of HLA-B27. But the frequency of HLA-B27 in the population-at-large far exceeds that of spondyloarthritis, suggesting other genetic factors also are operative. Other major histocompatibility complex genes have been implicated, especially HLA-DR, though linkage to HLA-B27 confounds the analysis of this in many studies. Genome-wide scans have implicated regions on chromosomes 2q, 6p, 6q, 10q, 11q, 16q, 17q, and 19q in ankylosing spondylitis, on 4, 6p, and 17q in psoriasis, and on 7q and 16q in inflammatory bowel disease. The search for non-major histocompatibility complex candidate genes has been complicated by inadequate power, because of the small effect they exert on overall disease susceptibility, although recent studies are revealing promising candidates that must be confirmed by other groups.

Human leukocyte antigen distribution in Israeli patients with psoriatic arthritis

OBJECTIVES

This study was designed to investigate the distribution of human leukocyte antigen (HLA) classes I and II in a group of Israeli Jewish patients with psoriatic arthritis (PsA) and identify HLA markers related to disease manifestation in PsA.

PATIENTS AND METHODS

Human leukocyte antigens class I and class II (both serologically and from oligotyping) were tested in a group of 50 consecutive patients with PsA, 32 with skin psoriasis (PSO), and 255 healthy persons. Data on age, gender, disease duration, and pattern of rheumatological manifestations-oligoarthritis, polyarthritis, spinal involvement, involvement of distal interphalangeal joints (DIPs), and enthesitis-were registered.

RESULTS

Human leukocyte antigens A3, B13, and B38 alleles were found to be significantly prevalent in PsA compared with PSO patients and healthy controls. HLA-B27 was found in only two out of 50 patients with PsA. Patients with PSO and PsA had significantly increased incidence of HLA-DRB0101 and -DRB0301, while the frequency of HLA-DRB0403 was significantly higher among patients with PsA of Ashkenazi origin. We found a statistically significant association between DIP involvement and the presence of HLA-A26 and -B38, while HLA-DRB0301 was related to spinal involvement.

CONCLUSIONS

Psoriatic arthritis in Israeli patients seems to be associated with the presence of HLA-A3, -B13, -B38, -DRB0101, and -DRB0301. HLA-B27 was not a marker of PsA in this cohort of patients, including patients with psoriatic spondyloarthropathy.

Genetic epidemiology. Psoriatic arthritis

The existence of psoriatic arthritis as a distinct clinical entity remains a topic of debate; some authors propose that it is simply the co-occurrence of psoriasis and inflammatory arthritis. However, a distinct entity is likely to have distinct susceptibility factors in addition to those that contribute to psoriasis and inflammatory arthritis alone. These aetiological factors may be genetic and/or environmental, and in this review, the evidence for distinct psoriatic arthritis genetic susceptibility factors is considered.

Psoriatic arthritis joint fluids are characterized by CD8 and CD4 T cell clonal expansions appear antigen driven

The CD8 alphabetaT cell receptor repertoire in joint fluid of individuals with active psoriatic arthritis contained an average of 32 major oligoclonal expansions in many variable genes of the TCR beta chain (BV) families, as shown by beta-chain CDR3 length analysis. Interestingly, a small number of oligoclonal expansions were shared between simultaneous samples of joint fluid and blood; however, most expansions found in joint fluid were not identifiable in blood emphasizing the immunologic specificity of the clonal events for the inflamed joint at a given point of time. The CD4 T cell joint fluid repertoire contained fewer and smaller oligoclonal expansions also largely restricted to the joint, suggesting that CD4 T cells participate perhaps by interacting cognitively to generate the CD8 clones. The inferred amino acid sequence of a single CD8 oligoclonal expansion revealed that they usually are composed of one or a few structurally related clones at the amino acid sequence level with beta-chains that encode identical or highly homologous CDR3 motifs. These were not shared among patients. Moreover, several clones that encoded the same amino acid sequence were found to be structurally distinct at the nucleotide level, strongly implying clonal selection and expansion is operating at the level of specific TCR-peptide interactions. The findings support a model of psoriatic arthritis inflammation involving extensive and selective Ag, likely autoantigen, driven intra-articular CD4, and CD8 T cell clonal expansions.

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.

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.

HLA-CW*0602 is a susceptibility factor in type I psoriasis, and evidence Ala-73 is increased in male type I psoriatics

We investigated the HLA-C locus of 87 unrelated patients with chronic plaque psoriasis by genotyping with sequence-specific amplification primers. The HLA-Cw*0602 allele was significantly increased in male and female type I psoriatics but not significantly increased in either male or female type II psoriatics. The overall frequency of Ala-73 (present in Cw*04, Cw*0602, Cw*07, Cw*12, Cw*1503, and Cw*17) in psoriatics was 88.5% but the incidence of Ala-73 in our Caucasian controls was also high at 84.3%. Ala-73 was present in 97.2% of type I and 85.7% of type II male psoriatics (chi2 = 8.43, p = 0.001; chi2 = 0.01, p = nonsignificant, respectively), in contrast to 81.5% of type I and 80% of type II female psoriatics (nonsignificant). HLA-Cw*0602 appeared more discriminating in determining disease susceptibility in our population than Ala-73, in line with earlier serologic studies implicating HLA-Cw6. Thus, although the frequency of HLA-Cw*0602 decreased from 54.0% in type I to 29.2% in type II psoriatics, the overall frequency of Ala-73, present in 90.4% of type I and 83.3% of type II psoriatics, did not. (i) Thus this study confirms the strong association between psoriasis and HLA-Cw*0602 by using sequence-specific amplification primers. (ii) Results show that Ala-73 on HLA-C molecules is increased in frequency in psoriasis, but results observed show an association more subtle than previously thought, with HLA-Cw*0602 playing the major role. (iii) This report documents the differential association of HLA genes in male and female psoriatic patients. An interaction between gender and immunogenetics may influence susceptibility to psoriasis.

Immunogenetic profile of psoriasis vulgaris: association with haplotypes A2,B13,Cw6,DR7,DQA1*0201 and A1,B17,Cw6,DR7,DQA1*0201

Psoriasis vulgaris is a skin disease with an immunological and genetic background present in 1-3% of the population. We studied the genetic susceptibility to psoriasis vulgaris in Finns with serological HLA typing and genomic HLA class II typing of the DQ and DP loci to evaluate the risk of developing psoriasis. The haplotypes most frequently distinguishing between psoriatics and controls were those that carried Cw6 (P < 10(-8)), DQA1*0201 (P = 9.3 x 10(-6)) and DR7 (P = 3.9 x 10(-5)). The two most frequent marker haplotypes were A2,B13,Cw6,DR7, DQA1*0201 and A1,B17,Cw6,DR7,DQA1*0201, which were not found among the control subjects. A deficit of haplotype B8,DR3,DQ2 (2 out of 124 in the patients versus 15 out of 106 in the controls, P = 1.5 x 10(-4)) was found, and this was in accordance with a slightly decreased frequency of DQA1*0501 (P = 3.1 x 10(-2)), which was usually linked with this haplotype. These results stimulate the research for a genetic resistance factor in psoriasis. Thus, this report sheds further light on the immunogenetic background of psoriasis in Finland. We conclude that the inheritance of psoriasis has a polygenic mode, in which the Cw6,DR7,DQA1*0201 combination seems to be important (P = 7.5 x 10(-7), relative risk 24.4, aetiological factor 0.29).

Do specific pockets of HLA-C molecules predispose Jewish patients to psoriasis vulgaris?

BACKGROUND

Psoriasis vulgaris was reported to be associated with a specific alanine residue at position 73 of HLA-C alleles in Japanese patients.

OBJECTIVE

Our purpose was to determine the role of HLA genes in susceptibility to psoriasis vulgaris in the Israeli Jewish population.

METHODS

Twenty-eight Israeli patients were analyzed for their HLA class I and II specificities by means of serologic and molecular methods.

RESULTS

All patients possessed in their HLA-C antigens an alanine residue at position 73 (p < 0.002). A significantly increased frequency of HLA-Cw6 and of Cw7 was also observed among the patients (p < 0.02).

CONCLUSION

Our study clearly shows that alanine in position 73 is significantly associated with psoriasis vulgaris in Jewish patients. Cw6 and Cw7 have a unique antigen-binding pocket containing both alanine at position 73 and a negatively charged aspartic acid at position 9. These residues are most probably important in determining the conformation of the C pocket and in turn the nature of the peptide bound to it. We suggest that this combination confers the highest risk of the development of psoriasis vulgaris.

Osteoarthritis in 84 Japanese patients with palmoplantar pustulosis

BACKGROUND

Palmoplantar pustulosis (PPP) is often associated with osteoarthritis. The relation between osteoarthritis in PPP and other types of seronegative arthritis remains unclear.

OBJECTIVE

The purpose of this study was to investigate the distribution and the frequency of osteoarthritis in patients with PPP and to compare HLA antigen frequencies in osteoarthritis in PPP, psoriatic arthritis, and ankylosing spondylitis.

METHODS

Clinical findings were identified and HLA-A, -B, -C, and -DR were determined in 84 Japanese patients with PPP. Bone scintigraphic studies were conducted for forty-one patients.

RESULTS

In addition to the anterior aspect of the chest wall, the knee, spine, and ankle were frequently involved. HLA-DR9 frequency was the highest in patients with PPP who had osteoarthritis.

CONCLUSION

Involvement of the knees, spine, ankles, and the anterior aspect of the chest wall was noted in patients with osteoarthritis and PPP. Osteoarthritis in PPP seems to be a distinct entity from a genetic point of view.

Alanine at position 73 of HLA-C is associated with psoriasis vulgaris in Finland

A close association was found between a specific sequence of HLA-C and psoriasis vulgaris in Finnish patients (chi 2 = 18.4, P = 1.78 x 10(-5)). This sequence codes for alanine at position 73 of the HLA-C molecule in the antigen binding cleft, and alanine may play a role in susceptibility to the disease.

Increased IgA antibodies to cytokeratins in the spondyloarthropathies

OBJECTIVES

Increased levels of IgA antibodies to cytokeratin-18 (CK-18) and epidermal keratins (EpK) in the sera of patients with rheumatoid arthritis (RA) have been demonstrated previously. In the present study investigations were carried out to determine whether levels of these autoantibodies were also raised in the spondyloarthropathies, and whether there was any association with particular disease manifestations.

METHODS

Using specific enzyme linked immunosorbent assays (ELISA) measurements were taken of IgA, IgG and IgM antibodies to EpK and to CK-18 in the sera of patients with psoriatic arthropathy, ankylosing spondylitis (AS), Reiter's syndrome, psoriasis and in normal subjects.

RESULTS

IgA antibodies to both EpK and CK-18 were significantly increased in sera from patients with psoriasis and psoriatic arthropathy but not in the sera from the patients with AS or Reiter's syndrome, or in the controls. In psoriatic arthritis, however, these levels were significantly higher only in those patients with peripheral joint disease and not in those with axial arthritis alone. There was no significant increase in antibody levels in patients with AS or Reiter's syndrome. There were no differences in the levels of IgG or IgM antibodies to CK-18 or EpK between the patient groups and controls.

CONCLUSIONS

Raised levels of IgA antibodies to CK-18 and EpK in psoriatic arthropathy and psoriasis probably reflect exposure of intracellular cytokeratin antigens to the immune system after damage to cytokeratin containing cells, and suggests a common pathogenic mechanism in these conditions which involves production of cytokeratin autoantibodies. In patients with psoriatic arthropathy, such a mechanism appears only to be operating in patients with peripheral joint involvement and not in those with axial arthritis.

Psoriatic arthritis. Genetics and HLA antigens

There is convincing evidence of a genetic basis for both psoriasis and psoriatic arthritis (PsA). Part of this genetic predisposition is due to genes within the major histocompatibility complex (MHC). In psoriasis, the primary association is with HLA-Cw6. Further work on specific nucleotide frequencies, especially those in the alpha 1 domain helix of the HLA-C molecule, will be of interest in determining whether a specific nucleotide frequency is present in all patients. The situation in PsA is considerably more complex. It is now established that there is an association between HLA-B27 and PsA, both in its peripheral arthropathy and in spinal disease in which radiological sacroiliitis is present. Spinal disease without radiological sacroiliitis is probably not associated with HLA-B27. There is some suggestion that HLA-B16 or its splits, HLA-B38 and HLA-B39, may also be associated with PsA, but there is considerable heterogeneity between the series, which prevents a firm conclusion being made. It is possible, but again not conclusive, that there is an association between HLA-DR4 and the symmetrical seronegative pattern of peripheral PsA. It is also likely that genes outwith the MHC predispose to psoriasis and PsA. It is further likely that a role will be found for environmental factors in both psoriasis and PsA. There is a tantalizing possibility of a complex interplay between a variety of environmental factors and genetic factors, both within and outwith the MHC, determining not only susceptibility but also the individual clinical pattern of disease. Further clarification of these possibilities is likely to depend primarily on understanding the role of genes within the MHC in predisposing to comparatively more homogeneous diseases, such as psoriasis and ankylosing spondylitis, before the mechanisms operating in PsA can be analysed and better understood.

Thyroid involvement in chronic inflammatory rheumatological disorders

The association between rheumatological and thyroid disorders has long been known, the most common being the association of rheumatoid arthritis and autoimmune thyroiditis. Little is known as to possible thyroid involvement in other rheumatological disease of possible autoimmune aetiology, such as psoriatic arthritis and ankylosing spondylitis. We measured thyroid volume and function as well as the prevalence of anti-microsome and anti-thyroglobulin antibodies in 107 consecutive patients with rheumatoid arthritis, 42 patients with psoriatic arthritis, and 12 male patients with ankylosing spondylitis. Fifty-two normal subjects were used as controls. The average thyroid volume, measured at ultrasounds, was increased in all groups of patients, and the prevalence of thyroid enlargement (A-P diameter > 20 mm) was 2-3 fold higher in rheumatological disorders in comparison to controls. Both, patients with rheumatoid arthritis and psoriatic arthritis had higher-than-normal fT4 levels and an increased prevalence of anti-microsome antibodies. In the rheumatoid arthritis group alterations in thyroid volume and function were present irrespective of disease activity, whereas in psoriatic arthritis thyroid involvement was confined to patients with active disease. Our data are consistent with a significant thyroid involvement in rheumatological disorders, which is not limited to diseases with a definite autoimmune aetiology.

Family history, smoking habits, alcohol consumption and risk of psoriasis

We have conducted a multicentre case-control study to assess the epidemiological importance of previously suggested risk factors for psoriasis, including family history of the disease, smoking and alcohol consumption. Newly diagnosed psoriatics, with a history of skin manifestations no longer than 2 years were eligible as cases; as controls we selected subjects with newly diagnosed dermatological conditions other than psoriasis. Interviews were performed by trained medical investigators using a structured questionnaire. Two-hundred and fifteen cases, aged 16-65 years (median age 38), and 267 controls, aged 15-65 years (median age 36), were interviewed and included in the analysis. Family history was a risk factor for psoriasis; the multiple logistic regression (MLR) adjusted-odds ratio was 18.8 (95% confidence interval 6.4-54.8) for a history in parents, and 3.2 (95% confidence interval 1.5-6.6) for a history in siblings. The risk of psoriasis was higher for current smokers than for those who had never smoked. The MLR adjusted odds ratio was 2.1 (95% confidence interval 1.1-4.0) for people smoking 15 cigarettes or more per day. The risk of psoriasis was higher for alcohol drinkers: compared with teetotallers the MLR adjusted-odds ratios were 1.3 (95% confidence interval 0.8-2.3) for subjects drinking one or two drinks/day and 1.6 (95% confidence interval 0.9 to 3.0) for those drinking three or more. However, the trend in risk was not statistically significant. Our study confirms the role of family history in psoriasis and provides some evidence of a dose-response relationship for an association between smoking habits and psoriasis.

T cell receptor V-segment frequencies in peripheral blood T cells correlate with human leukocyte antigen type

We compared T cell receptor (TCR) V-segment frequencies in human leukocyte antigen (HLA) identical siblings to sibling pairs who differ at one or both HLA haplotypes using four V beta-specific and one V alpha-specific monoclonal antibody. In every one of nine families HLA-identical sibs had the most similar patterns of V-segment frequencies in their peripheral blood, whereas totally mismatched sibs were, in general, the most dissimilar; HLA haploidentical sibs tended to be intermediate between the two groups. The degree of similarity among HLA-identical sibs was comparable to that observed among three pairs of identical twins suggesting that HLA is the major genetic component influencing TCR V-segment frequency. Consistent with this observation, it was found that the frequency of T cells expressing particular V beta segments was skewed towards either CD4+ or CD8+ cells indicating that T cells expressing some V beta genes may be positively selected primarily by class I or class II major histocompatibility complex proteins. Finally, it was observed that individuals who express the HLA class I specificity, B38, tend to express high levels of V alpha 2.3+ cells among their CD8+ T cells. These observations represent definitive proof that human V-segment frequencies are profoundly influenced by the HLA complex.

Genetically determined coincidence of Kaposi sarcoma and psoriasis in an HIV-negative patient after prednisolone treatment. Spontaneous regression 8 months after discontinuing therapy

We report the case of drug-induced, acrolocalized Kaposi sarcoma (KS), arising multicentrically in both palms and soles of a male patient who has had widespread psoriasis since 12 years of age. This 59-year-old man, of Mediterranean origin, was HIV antibody-negative and had received oral prednisolone treatment over 5 months for chronic obstructive lung disease (initial dose: 75 mg/d). Eight months after discontinuing oral treatment the KS nodules regressed spontaneously and finally disappeared completely without additional treatment. Light and electron microscopic investigations confirmed the diagnosis of KS, whereas laboratory tests excluded HIV infection and suggested mild immune dysfunction. The existence of HLA loci predisposing to KS and to psoriasis (A1, DR5, DR7, DR11) was characteristic for the simultaneous occurrence of these two diseases. This case report demonstrates the complex interrelationships between genetic predisposition, drugs leading to immune suppression, and the evolution of an unusual neoplasm.