HLA-DRB1*04 alleles in psoriatic arthritis: comparison with rheumatoid arthritis and healthy controls

Paediatric Acute onset Neuropsychiatric Syndrome: Exploratory study finds no evidence of HLA class II association but high rate of autoimmunity in first-degree relatives

AIM

Paediatric acute-onset neuropsychiatric syndrome (PANS) is defined by an acute onset of obsessive-compulsive disorder and/or eating restrictions and at least two other severe neuropsychiatric symptoms. The condition is suspected to have an immune-mediated pathophysiology, but reliable biomarkers have not been identified.

METHODS

We hypothesised that PANS, like narcolepsy, might have a human leucocyte antigen (HLA) association, as found in 95% of children developing narcolepsy after H1N1 immunisation. Low resolution genotyping of the MHC class II antigens HLA-DRB1 and HLA-DQB1 was performed using two different PCR-based methods. In addition, parents were interviewed regarding a detailed family history of autoimmune diseases in first-degree relatives. A total of 18 children, aged 5-14 (mean 8.2) years at onset of PANS met symptom criteria.

RESULTS

No evident association between PANS and the specific HLA alleles examined was observed. In first-degree relatives of 10 of the 18 children, an autoimmune disease had been diagnosed, and three of the 18 children themselves had an autoimmune disease.

CONCLUSION

No HLA allele association such as seen in children with narcolepsy after H1N1 immunisation could be confirmed in this group of children with PANS. However, more than half the group had a first-degree relative with a diagnosed autoimmune disease.

Advanced genomics and clinical phenotypes in psoriatic arthritis

Psoriatic Arthritis (PsA) is a complex polygenic inflammatory disease showing a variable musculoskeletal involvement in patients with skin psoriasis. PsA coexist in 25-40 % of patients with the dermatological manifestations, but PsA may also predate the appearance of psoriasis. Nonetheless, the immunopathogenesis of psoriasis and PsA manifest significant similarities, with a major role of the individual susceptibility in both cases. Genome wide association studies (GWAS) identified several genes/loci associated with the risk to develop PsA, both dependent and independent of psoriasis. The major challenge is thus represented by the need to translate the identification of functional polymorphisms and other genetics findings into biological mechanisms along with the identification of novel putative drug targets. A functional genomics approach aims to increase GWAS power and recent evidence supports the use of a multilayer process, including eQTL, methylome, chromatin conformation analysis and genome editing to discover novel genes that can be affected by disease-associated variants, such as PsA. The available data have considered PsA as a unique homogeneous clinical entity while the clinical experience supports a wide variability of skin and joint manifestations coexisting in diverse patients with different mechanisms underlying the musculoskeletal and dermatological domains. A better discrimination of the patient features is encouraged by the limited data on functional genomics. We provide herein a review of the latest findings on PsA functional genomics highlighting the exciting developments in the field and how these might lead to a better understanding of gene regulation underpinning disease mechanisms and ultimately refine clinical phenotyping.

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

OBJECTIVE

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

PATIENTS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Immunogenetics of drug-induced skin blistering disorders. Part II: Synthesis

The overall immunopathogenesis relevant to a large series of disorders caused by a drug or its associated hyperimmune condition is discussed based upon examining the genetics of severe drug-induced bullous skin problems (sporadic idiosyncratic adverse events including Stevens–Johnson syndrome and Toxic epidermal necrolysis). New results from an exemplar study on shared precipitating and perpetuating inner causes with other related disease phenotypes including aphtous stomatitis, Behçets, erythema multiforme, Hashimoto’s thyroiditis, pemphigus, periodic fevers, Sweet’s syndrome and drug-induced multisystem hypersensitivity are presented. A call for a collaborative, wider demographic profiling and deeper immunotyping in suggested future work is made.

Psoriasis and psoriatic arthritis: separate or one and the same?

The presence and severity of skin and joint symptoms in patients with psoriasis and psoriatic arthritis frequently do not correspond, a discrepancy that has raised the question of whether they represent two related but different disease processes. The fact that some agents seem to work preferentially in one state over the other reinforces this idea. However, there are also several agents with combined efficacy against cutaneous and articular inflammation that appear to support the existence of a common aetiology. Here we review the clinical, epidemiological and genetic evidence for and against a common pathogenesis for the two diseases. We then discuss the cellular and molecular targets of their selected therapies and how they potentially implicate effector pathways as a common immunopathogenic mechanism. Finally, we examine a recently proposed model of psoriasis pathogenesis involving type 1 interferon-producing plasmacytoid dendritic cells and how it may provide further clues to the aetiological links between psoriasis and psoriatic arthritis.

Investigating the role of the HLA-Cw*06 and HLA-DRB1 genes in susceptibility to psoriatic arthritis: comparison with psoriasis and undifferentiated inflammatory arthritis

Objective:

Psoriasis of early onset (type I; age of onset ⩽40 years) is associated with HLA-Cw*06 while the shared epitope (SE) is associated with rheumatoid arthritis susceptibility. Our aim was to investigate the role of HLA-Cw*06 and HLA-DRB1 genes (including SE) with psoriatic arthritis (PsA) susceptibility.

Methods:

In a case–control association study, HLA-Cw*06 phenotype frequencies were compared between patients with PsA (n = 480), psoriasis alone (n = 611) and healthy controls (n = 166). Similarly, at the HLA-DRB1 locus, phenotype and SE frequencies were compared in patients with PsA (n = 480), early undifferentiated inflammatory arthritis alone (n = 1621) and healthy controls (n = 537).

Results:

The HLA-Cw*06 phenotype was associated with type I psoriasis (OR 6.9, 95% CI 4.4, 11.1, p = 2.2×10⁻²¹) and with patients with PsA having type I psoriasis (OR 5.0, 95% CI 3.2, 7.9, p = 4.39×10⁻¹³), but not with patients with PsA having type II psoriasis (age of onset >40 years). HLA-DRB1*07, in linkage disequilibrium with HLA-Cw*06, was also associated with patients with PsA having type I psoriasis (OR 2.7, 95% CI 2.1, 3.7, p<0.00001). HLA-DRB1*04 alleles and the SE were associated with undifferentiated inflammatory arthritis but not with PsA.

Conclusions:

The SE is not a PsA susceptibility locus. HLA-Cw*06 and HLA-DRB1*07 are associated with patients with PsA having type I psoriasis, suggesting that the primary association is with age of onset of psoriasis. Patients with PsA having type I psoriasis, therefore, have a genetic background different to those with type II psoriasis, and adjustment for this is necessary in future studies that investigate the genetic susceptibility of PsA.

Increased prevalence of the metabolic syndrome in patients with moderate to severe psoriasis

The role of chronic inflammation causing metabolic and vascular disorders is increasingly recognized. It is hypothesized that proinflammatory cytokines contribute to atherogenesis, peripheral insulin resistance, and the development of hypertension and type II diabetes. Psoriasis as a chronic inflammatory skin disorder is characterized by a variety of immunologic and inflammatory changes and may similarly predispose for those disorders. The objective of this study was to elucidate the association of psoriasis with chronic vascular and metabolic disorders. We investigated a total of 581 adult patients hospitalised for plaque type psoriasis as compared to 1,044 hospital-based controls. A distinct pattern of chronic disorders was found to be significantly associated with psoriasis, including diabetes mellitus type II [odds ratio (OR)=2.48], arterial hypertension (OR = 3.27), hyperlipidemia (OR = 2.09), and coronary heart disease (OR = 1.95). The combined presence of these conditions together with obesity, known as the metabolic syndrome, was clearly more prevalent in psoriasis patients (OR = 5.29). In addition, psoriasis patients were significantly more likely to be smokers (OR = 2.96) and to have a regular or heavy consumption of alcohol (OR = 3.33 and 3.61, respectively). In conclusion, psoriasis patients appear to be at higher risk for diabetes mellitus and cardiovascular disease. This could likely be due to the effects of chronic inflammatory changes, in particular the secretion of proinflammatory cytokines. The risk of late term cardiovascular complications might support the use of systemic treatment in psoriasis.

HLA-DRB1 association in Saudi rheumatoid arthritis patients

Association between HLA-DRB1 alleles and rheumatoid arthritis (RA) has been known for more than three decades. However, the strength of these links varies between ethnic groups. This study examines the frequency of HLA-DRB1 alleles amongst Saudi RA patients. The DRB1 region of major histocompatibility complex was screened by polymerase chain reaction/sequence specific primers (PCR/SSP) in a total of 140 subjects including 70 RA patients and 70 matched healthy controls. HLA-DRB1 *04 was found to be the most frequent allele associated with RA followed by DRB1 *08 and DRB1 *10. On the other hand, the frequency of DRB1*06 was found to be decreased in RA patients as compared to controls. Molecular sub typing of the most prevalent allele DRB1 *04 revealed a statistically significant association between RA and DRB1 *0405. We conclude that an improved understanding about the influence of HLA on RA might help in predicting the susceptibility or protection against disease.

Discordant expression of HLA class II-associated co-chaperones and HLA-DRB alleles in cultured fibroblast-like synoviocytes

Human leukocyte antigen (HLA)-DR-positive synovial fibroblasts are frequently observed in rheumatoid arthritis (RA) and may be implicated in the autoimmune reaction because RA is associated with certain HLA-DRB1* alleles. The question of whether components of the class II antigen presentation pathway and specific DRB alleles are efficiently expressed by synovial fibroblasts is germane to this hypothesis. To address this, cultured fibroblast-like synoviocytes (cFLS) were analyzed for constitutive and interferon (IFN)-gamma-induced expression of specific DRB alleles and class II-associated cochaperones. IFN-gamma induction of invariant chain, DM, and DR molecules was observed in all cFLS, but expression of specific DR allotypes was variable. Interestingly, DM-modulated epitopes on RA-associated DR molecules were either absent or delayed, despite strong DM expression and a paucity of major histocompatibility complex/class II-associated invariant chain peptide complexes. Altered expression of specific peptide-dependent epitopes on RA-associated HLA-DR molecules suggests differences in antigen presentation by cFLS, which may have implications for the immunopathogenesis of RA.

A susceptibility gene for psoriatic arthritis maps to chromosome 16q: evidence for imprinting

Several genetic loci have been reported for psoriasis, but none has been specifically linked to psoriatic arthritis (PsA), a condition that affects >10% of patients with psoriasis. A genetic component for PsA is suggested by segregation within families and high concordance among identical twins. We performed a linkage scan to map genes contributing to PsA. We identified 178 patients with PsA out of 906 patients who were included in our genetic study of psoriasis. Using a comprehensive genealogy database, we were able to connect 100 of these into 39 families. We genotyped the patients using a framework marker set of 1,000 microsatellite markers, with an average density of 3 cM, and performed multipoint, affected-only, allele-sharing linkage analysis using the Allegro program. On the basis of the initial results, we genotyped more markers for the most prominent loci. A linkage with a LOD score of 2.17 was observed on chromosome 16q. The linkage analysis, conditioned on paternal transmission to affected individuals, gave a LOD score of 4.19, whereas a LOD score of only 1.03 was observed when conditioned for maternal transmission. A suggestive locus on chromosome 16q has previously been implicated in psoriasis. Our data indicate that a gene at this locus may be involved in paternal transmission of PsA.

Current concepts in psoriatic arthritis

This review summarizes articles written about psoriatic arthritis in the past year. It concentrates on clinical and epidemiologic issues, pathogenesis and treatment, and updates the reader regarding new concepts in psoriatic arthritis.