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

The effect of paternal psoriasis on neonatal outcomes: a nationwide population-based study

Background

Psoriasis is a chronic autoimmune disease involving both environmental and genetic risk factors. Maternal psoriasis often results in poor pregnancies that influence both mothers and newborns. However, the influence of paternal psoriasis on the newborn remains unknown. The aim of this study was to investigate whether paternal psoriasis is associated with increased risk of adverse neonatal outcomes, within a nationwide population-based data setting.

Methods

Singleton pregnancies were identified in the Taiwan National Health Insurance database and National Birth Registry between 2004-2011 and classified into four study groups according to whether mothers and spouses had psoriasis (paternal(-)/maternal(-), paternal(+)/maternal(-), paternal(-)/maternal(+), and paternal(+)/maternal(+)). Data were analyzed retrospectively. Adjusted odds ratios (aOR) or hazard ratios (aHR) were calculated to evaluate the risk of neonatal outcomes between groups.

Results

A total of 1,498,892 singleton pregnancies were recruited. Newborns of fathers with psoriasis but not of mothers with psoriasis were associated with an aHR (95% CI) of 3.69 (1.65-8.26) for psoriasis, 1.13 (1.06-1.21) for atopic dermatitis and 1.05 (1.01-1.10) for allergic rhinitis. Newborns of mothers with psoriasis but not of fathers with psoriasis were associated with an aOR (95% CI) of 1.26 (1.12-1.43) for low birth weight (<2500 g) and 1.64 (1.10-2.43) for low Apgar scores, and an aHR of 5.70 (2.71-11.99) for psoriasis.

Conclusion

Newborns of fathers with psoriasis are associated with significantly higher risk of developing atopic dermatitis, allergic rhinitis and psoriasis. Caution is advised for adverse neonatal outcomes when either or both parents have psoriasis.

Sex- and gender-related differences in psoriatic arthritis

Psoriatic arthritis (PsA) is an inflammatory musculoskeletal disease with a chronic, progressive course. Various aspects of PsA, including its clinical features, disease course and response to treatment, are influenced by sociodemographic characteristics of the patient. This includes patient sex, the biological attributes associated with being male or female, and gender, a sociocultural construct that comprises attitudes, traits and behaviours associated with being a man or a woman. An understanding of sex- and gender-related differences in PsA, as well as their underlying mechanisms, is therefore important for individualized care. In this narrative review, the influence of sex and gender on PsA manifestation and course, patient function and quality of life, and their association with comorbidities are described. Sex- and gender-related disparities in response to advanced therapies and their potential underlying mechanisms are delineated. Differences in pathophysiological mechanisms between male and female patients including genetics, immune and hormonal mechanisms are discussed. Finally, fertility and pregnancy outcomes in PsA are outlined. By adopting sex and gender lenses, this review is aimed at highlighting key differences between male and female patients with PsA and uncovering mechanisms underlying these differences, ultimately promoting individualized care of men and women with PsA and informing future research in this area.

Etiopathogenesis of Psoriasis from Genetic Perspective: An updated Review

Psoriasis is an organ-specific autoimmune disease characterized by the aberrant proliferation and differentiation of keratinocytes, leading to skin lesions. Abnormal immune responses mediated by T cells and dendritic cells and increased production of inflammatory cytokines have been suggested as underlying mechanisms in the pathogenesis of psoriasis. Emerging evidence suggests that there is a heritable basis for psoriatic disorders. Moreover, numerous gene variations have been associated with the disease risk, particularly those in innate and adaptive immune responses and antigen presentation pathways. Herein, this article discusses the genetic implications of psoriatic diseases' etiopathogenesis to develop novel investigative and management options.

Sex-Based Medicine Meets Psoriatic Arthritis: Lessons Learned and to Learn

Humorally associated autoimmune diseases generally show a female predominance whereas ankylosing spondylitis, a disease that overlaps with psoriatic arthritis (PsA), shows a male predominance. The present review ascertains the current knowledge of sex-specific differences related to psoriatic arthritis (PsA), a chronic, inflammatory condition associated with psoriasis. Sex differences may have important implications for clinical research in PsA and in terms of epidemiology (incidence, prevalence, lifetime risk, survival, and mortality), clinical, radiological, and laboratory features, and response to treatment. While nationwide surveys and large-scale databases and registries show no sex-specific differences, varying male/female ratios have been reported, ranging from 0.42 to 2.75 (comparable with those reported for psoriasis vulgaris: ranging from 0.28 to 2.38). This may reflect subtle, complex, nonlinear interactions between the biological make-up of the individual (genetic and epigenetic differences), hormonal components including menopausal status, environmental exposures including skeletal physical stressing, and psychological variables. There exists methodological heterogeneity and paucity of data concerning sex-specific differences, in terms of the specific population studied, study design, and the diagnostic criteria utilized. Harmonizing and reconciling these discrepancies would be of crucial importance in achieving the ambitious goals of personalized/individualized medicine and further standardized meta-data and Big Data could help disentangle and elucidate the precise mechanisms of underlying potential PsA sex-specific differences.

Genetics, Epigenetics, and Gender Impact in Axial-Spondyloarthritis Susceptibility: An Update on Genetic Polymorphisms and Their Sex Related Associations

Spondyloarthritis (SpA) is a group of chronic inflammatory rheumatic disease that can be divided into predominantly axial or predominantly peripheral involvement, with or without associated psoriasis, inflammatory bowel disease or previous infection. Axial SpA (axSpA) encompasses ankylosing spondylitis (AS) with radiological sacroiliitis, and a type without radiographic sacroiliitis, called “non-radiographic axial SpA” (nr-axSpA). Males and females show large differences in their susceptibility to SpA, such as distinctions in clinical patterns, phenotypes and in therapeutical response, particularly to TNF inhibitors (TNFi). Several studies indicate that AS women have doubled risk to failure TNFi compared with males. This diversity in drugs’ efficacy among women and men may be caused by differences in the balance of sex hormones and in gene-specific expression likely triggered by X-chromosome instability and gene-specific epigenetic modifications. Evidence reported that polymorphisms in microRNAs on X- and other chromosomes, such as miR-146a, miR-155, miR-125a-5p, miR-151a-3p and miR-22-3p, miR-199a-5p could be involved in the different clinical presentation of SpA, as well as disease activity. In addition, association with non−response to TNFi treatment and presence of IRAK3 and CHUCK genes in SpA patients was recently detected. Finally, polymorphisms in genes involved in IL-23/IL-17 pathway, such as in drug pharmacodynamics and pharmacokinetics may have a role in response to TNFi, IL17i, and IL23i. A major understanding of genomic variability could help in the development of new therapeutic targets or in taking advantages of different mechanisms of action of biological drugs. Moving from the multifactorial etiology of disease, the present review aims at evaluating genetic and epigenetic factors and their relationship with sex and bDMARDs response, helping to investigate the different expression among males and females of genes on X- and other chromosomes, as well as mi-RNA, to highlight relationships between sex and occurrence of specific phenotypes and symptoms of the disease. Moreover, the role of the epigenetic modification in relation to immune-regulatory mechanisms will be evaluated.

Insights into the pathogenesis of psoriatic arthritis from genetic studies

Psoriatic arthritis (PsA) is a relatively common inflammatory arthritis, a spondyloarthritis (SpA), that occurs most often in patients with psoriasis, a common immune-mediated inflammatory skin disease. Both psoriasis and PsA are highly heritable. Genetic and recent genomic studies have identified variants associated with psoriasis and PsA, but variants differentiating psoriasis from PsA are few. In this review, we describe recent developments in understanding the genetic burden of PsA, linkage, association and epigenetic studies. Using pathway analysis, we provide further insights into the similarities and differences between PsA and psoriasis, as well as between PsA and other immune-mediated inflammatory diseases, particularly ankylosing spondylitis, another SpA. Environmental factors that may trigger PsA in patients with psoriasis are also reviewed. To further understand the pathogenetic differences between PsA and psoriasis as well as other SpA, larger cohort studies of well-phenotyped subjects with integrated analysis of genomic, epigenomic, transcriptomic, proteomic and metabolomic data using interomic system biology approaches are required.

Not your average joint: Towards precision medicine in psoriatic arthritis

Precision medicine, propelled by advances in multi-omics methods and analytics, aims to revolutionize patient care by using clinically-actionable molecular markers to guide diagnostic and therapeutic decisions. We describe the applications of precision medicine in risk stratification, drug selection, and treatment response prediction in psoriatic arthritis, for which targeted, personalized approaches are steadily emerging.

Pathophysiology, Clinical Presentation, and Treatment of Psoriasis: A Review

IMPORTANCE

Approximately 125 million people worldwide have psoriasis. Patients with psoriasis experience substantial morbidity and increased rates of inflammatory arthritis, cardiometabolic diseases, and mental health disorders.

OBSERVATIONS

Plaque psoriasis is the most common variant of psoriasis. The most rapid advancements addressing plaque psoriasis have been in its pathogenesis, genetics, comorbidities, and biologic treatments. Plaque psoriasis is associated with a number of comorbidities including psoriatic arthritis, cardiometabolic diseases, and depression. For patients with mild psoriasis, topical agents remain the mainstay of treatment, and they include topical corticosteroids, vitamin D analogues, calcineurin inhibitors, and keratolytics. The American Academy of Dermatology-National Psoriasis Foundation guidelines recommend biologics as an option for first-line treatment of moderate to severe plaque psoriasis because of their efficacy in treating it and acceptable safety profiles. Specifically, inhibitors to tumor necrosis factor α (TNF-α) include etanercept, adalimumab, certolizumab, and infliximab. Other biologics inhibit cytokines such as the p40 subunit of the cytokines IL-12 and IL-13 (ustekinumab), IL-17 (secukinumab, ixekizumab, bimekizumab, and brodalumab), and the p19 subunit of IL-23 (guselkumab, tildrakizumab, risankizumab, and mirikizumab). Biologics that inhibit TNF-α, p40IL-12/23, and IL-17 are also approved for the treatment of psoriatic arthritis. Oral treatments include traditional agents such as methotrexate, acitretin, cyclosporine, and the advanced small molecule apremilast, which is a phosphodiesterase 4 inhibitor. The most commonly prescribed light therapy used to treat plaque psoriasis is narrowband UV-B phototherapy.

CONCLUSIONS AND RELEVANCE

Psoriasis is an inflammatory skin disease that is associated with multiple comorbidities and substantially diminishes patients' quality of life. Topical therapies remain the cornerstone for treating mild psoriasis. Therapeutic advancements for moderate to severe plaque psoriasis include biologics that inhibit TNF-α, p40IL-12/23, IL-17, and p19IL-23, as well as an oral phosphodiesterase 4 inhibitor.

Lessons learned from twins in autoimmune and chronic inflammatory diseases

Autoimmunity and chronic inflammation recognize numerous shared factors and, as a result, the resulting diseases frequently coexist in the same patients or respond to the same treatments. Among the convenient truths of autoimmune and chronic inflammatory diseases, there is now agreement that these are complex conditions in which the individual genetic predisposition provides a rate of heritability. The concordance rates in monozygotic and dizygotic twins allows to estimate the weight of the environment in determining disease susceptibility, despite recent data supporting that only a minority of immune markers depend on hereditary factors. Concordance rates in monozygotic and dizygotic twins should be evaluated over an observation period to minimize the risk of false negatives and this is well represented by type I diabetes mellitus. Further, concordance rates in monozygotic twins should be compared to those in dizygotic twins, which share 50% of their genes, as in regular siblings, but also young-age environmental factors. Twin studies have been extensively performed in several autoimmune conditions and cumulatively suggest that some diseases, i.e. celiac disease and psoriasis, are highly genetically determined, while rheumatoid arthritis or systemic sclerosis have a limited role for genetics. These observations are necessary to interpret data gathered by genome-wide association studies of polymorphisms and DNA methylation in MZ twins. New high-throughput technological platforms are awaited to provide new insights into the mechanisms of disease discordance in twins beyond strong associations such as those with HLA alleles.

Genetic, Epigenetic and Pharmacogenetic Aspects of Psoriasis and Psoriatic Arthritis

There is a strong familial component to psoriatic disease as well as a complex array of genetic, immunologic, and environmental factors. The dominant genetic effect is located on chromosome 6p21.3 within the major histocompatibility complex region, accounting for one-third of genetic contribution. Genome-wide association studies (GWAS) identified additional genes, including skin barrier function, innate immune response, and adaptive immune response genes. To better understand disease susceptibility and progression requires replication in larger cohorts, fine-mapping efforts, new technologies, and functional studies of genetic variants, gene-gene interactions and gene-environmental interactions. New technologies available include next-generation sequencing, copy number variation analysis, and epigenetics.

Genomic imprinting in psoriasis and atopic dermatitis: A review

Genomic imprinting is a genetic process where only one allele of a particular gene is expressed in a parent-of-origin dependent manner. Epigenetic changes in the DNA, such as methylation or acetylation of histones, are primarily thought to be responsible for silencing of the imprinted allele. Recently, global CpG methylation changes have been identified in psoriatic skin in comparison to normal skin, particularly near genes known to be upregulated in psoriasis such as KYNU, OAS2, and SERPINB3. Furthermore, imprinting has been associated with multi-chromosomal human disease, including diabetes and multiple sclerosis. This paper is the first to review the clinical and genetic evidence that exists in the literature for the association between imprinting and general skin disorders, including atopic dermatitis and psoriatic disease. Atopy was found to have evidence of imprinting on chromosomes 6, 11, 14, and 13. The β subunit of the IgE receptor on chromosome 11q12-13 may be imprinted. Psoriatic disease may be related to imprinting effects on chromosome 6 for psoriasis and 16 for psoriatic arthritis.

Indications for potential parent-of-origin effects within the FTO gene

Genome-Wide Association Studies (GWAS) were successfully applied to discover associations with obesity. However, the GWAS design is usually based on unrelated individuals and inheritance information on the parental origin of the alleles is missing. Taking into account parent-of-origin may provide further insights into the genetic mechanisms contributing to obesity. We hypothesized that there may be variants within the robustly replicated fat mass and obesity associated (FTO) gene that may confer different risk for obesity depending on transmission from mother or father. Genome-wide genotypes and pedigree information from the Sorbs population were used. Phased genotypes among 525 individuals were generated by AlphaImpute. Subsequently, 22 SNPs within FTO introns 1 to 3 were selected and parent-of-origin specific association analyses were performed using PLINK. Interestingly, we identified several SNPs conferring different genetic effects (P≤0.05) depending on parental origin—among them, rs1861868, rs1121980 and rs9939973 (all in intron 1). To confirm our findings, we investigated the selected variants in 705 German trios comprising an (extremely) obese child or adolescent and both parents. Again, we observed evidence for POE effects in intron 2 and 3 (P≤0.05) as indicated by the parental asymmetry test. Our results suggest that the obesity risk transmitted by several FTO variants may depend on the parental origin of the allele. Larger family-based studies are warranted to replicate our findings.

Familial aggregation of moderate to severe plaque psoriasis

BACKGROUND

Psoriasis is a highly heritable disease. It has been suggested that psoriasis is preferentially transmitted from fathers.

AIM

To evaluate the degree of familial aggregation of psoriasis; to determine the recurrence risk ratio (λR ) of psoriasis in first, second and third degree relatives of patients with psoriasis; and to investigate the transmission patterns of the disease and their relationships with the clinical profiles of patients.

METHODS

A cross-sectional study on 640 consecutive, unrelated adult patients with chronic plaque psoriasis was performed. The prevalence of psoriasis in first, second and third degree relatives of the patients was determined, and the λR was calculated under the assumption of a population prevalence of 2%. Age of onset and presence of facial, hand and foot psoriasis were evaluated in probands with paternal vs. maternal transmission.

RESULTS

A positive familial history of psoriasis was found in 380 patients (59.37%). Of these, 174 (27.18%) had at least one parent with psoriasis, with a λR of 13.59, while 106 patients (16.56%) had at least one second degree relative with psoriasis, and 34 patients (5.31%) had one third degree relative with psoriasis. No parent-of-origin effect in transmission of psoriasis from affected parent to offspring was observed, and there were no significant differences in the clinical profiles of the disease between patients grouped by transmission pattern of psoriasis.

CONCLUSIONS

These results show a high familial recurrence risk of psoriasis, and suggest a balanced parental transmission of the disease.

Gender differences in autoimmune disease

Autoimmune diseases are a range of diseases in which the immune response to self-antigens results in damage or dysfunction of tissues. Autoimmune diseases can be systemic or can affect specific organs or body systems. For most autoimmune diseases there is a clear sex difference in prevalence, whereby females are generally more frequently affected than males. In this review, we consider gender differences in systemic and organ-specific autoimmune diseases, and we summarize human data that outlines the prevalence of common autoimmune diseases specific to adult males and females in countries commonly surveyed. We discuss possible mechanisms for sex specific differences including gender differences in immune response and organ vulnerability, reproductive capacity including pregnancy, sex hormones, genetic predisposition, parental inheritance, and epigenetics. Evidence demonstrates that gender has a significant influence on the development of autoimmune disease. Thus, considerations of gender should be at the forefront of all studies that attempt to define mechanisms that underpin autoimmune disease.

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.

NOD2 expression is regulated by microRNAs in colonic epithelial HCT116 cells

BACKGROUND

Crohn's disease (CD) is associated with defective sensing of pathogens in genetically susceptible individuals. Nucleotide-binding oligomerization domain containing 2 (NOD2) mutations in coding regions are strongly linked to CD pathogenesis. Our laboratory has reported that microRNAs (miRNAs) are differentially expressed in CD. However, miRNA regulation of NOD2 remains unknown. This study was designed to determine whether miRNAs regulate NOD2 expression as well as downstream nuclear factor kappaB activation and inflammatory responses in colonic epithelial HCT116 cells.

METHODS

NOD2 and miRNA expression in stimulated HCT116 cells were assessed by quantitative reverse transcription-polymerase chain reaction. Regulation of NOD2 expression by miRNAs was determined by luciferase reporter construct assays and transfection of specific miRNA mimics. Regulation of NOD2 signaling and immune response by miRNAs was assessed by transfection of mimics followed by muramyl dipeptide stimulation.

RESULTS

Muramyl dipeptide-induced increases in NOD2, interleukin-8, and CXCL3 expression were inversely associated with miRNA expression. Overexpression of miR-192, miR-495, miR-512, and miR-671 suppressed NOD2 expression, muramyl dipeptide-mediated NF-κB activation, and messenger RNA expressions of interleukin-8 and CXCL3 in HCT116 cells. A single-nucleotide polymorphism (rs3135500) located in the NOD2 3'-untranslated region significantly reduced miR-192 effects on NOD2 gene expression.

CONCLUSIONS

To our knowledge, this is the first report demonstrating that miRNAs regulate NOD2 and its signaling pathway. Four miRNAs downregulate NOD2 expression, suppress NF-κB activity, and inhibit interleukin-8 and CXCL3 messenger RNA expression. Treatment of CD with miRNAs may represent a potential anti-inflammatory therapeutic strategy in CD patients with and without NOD2 gene mutations.

[Psoriasis: physiopathology and immunogenetics]

Psoriasis is a multifactorial disease that involves genetic, immunological and environmental factors. During the last decade, several studies by genome scan on families or cases/controls helped to highlight more than ten loci "PSORS" located on different chromosomes and containing several candidate genes. Psoriasis appears as a genetic disease that follows the mixed model with the involvement of a major gene (PSORS1) and a set of minor genes with a variable penetrance depending on the locus. Genetic data have focused on the involvement of the immune system in the pathogenesis of psoriasis. It is now accepted that psoriasis is an immunological disease involving the response profiles TH1 and TH17. Much remains to be done to better elucidate the mechanisms involved in the genesis of psoriatic lesions to find new therapeutic targets.

The HLA-Cw*06 allele and -1149 G/T polymorphism of extrapituitary promoter of PRL gene as a possible common genetic predisposing factors to psoriasis vulgaris and psoriatic arthritis in Czech population

Psoriatic arthritis (PsA) affects approximately 30 % of patients suffering from psoriasis vulgaris (PsV), but the risk factors for its development have not been well elucidated yet. The HLA-Cw*06 allele was described as a predisposing factor to PsV. Prolactin is known as an immune response modulator, and its elevated levels present risk for PsV development. It is possible that these factors interact and together emphasize the predisposition to both diseases. We tested on an association of HLA-Cw alleles and functional polymorphism -1149 G/T in PRL gene extrapituitary promoter with PsV and PsA in Czech population. We found a statistically significant association between HLA-Cw*06 allele and PsV (P corrected = 0.0013) that was most prominent in early onset disease subtype (P corrected = 0.0013). The association between HLA-Cw*06 and PsA was low (P corrected = 0.0585) and restricted to PsA patients with early PsV onset (P corrected = 0.0195). We found no association of -1149 G/T PRL gene polymorphism with either PsV or PsA.

Early psoriatic arthritis

Psoriatic arthritis is an inflammatory musculoskeletal disease associated with psoriasis that is usually seronegative for rheumatoid factor. Psoriatic arthritis affects men and women equally, usually during the fourth decade, although it may affect children and octogenarians. Psoriatic arthritis may lead to deformities, joint damage, reduced quality of life and function. Early detection and treatment may prevent untoward outcomes.

A role for epigenetics in psoriasis: methylated Cytosine-Guanine sites differentiate lesional from nonlesional skin and from normal skin

DNA methylation is one of several epigenetic mechanisms that can lead to stable and heritable changes in gene expression without changing the underlying DNA sequence. In this issue, Roberson et al. demonstrate that lesional skin in psoriasis is accompanied by changes in DNA methylation, which revert back to baseline with treatment, indicating that DNA methylation in psoriasis is dynamic.

A powerful test of parent-of-origin effects for quantitative traits using haplotypes

Imprinting is an epigenetic phenomenon where the same alleles have unequal transcriptions and thus contribute differently to a trait depending on their parent of origin. This mechanism has been found to affect a variety of human disorders. Although various methods for testing parent-of-origin effects have been proposed in linkage analysis settings, only a few are available for association analysis and they are usually restricted to small families and particular study designs. In this study, we develop a powerful maximum likelihood test to evaluate the parent-of-origin effects of SNPs on quantitative phenotypes in general family studies. Our method incorporates haplotype distribution to take advantage of inter-marker LD information in genome-wide association studies (GWAS). Our method also accommodates missing genotypes that often occur in genetic studies. Our simulation studies with various minor allele frequencies, LD structures, family sizes, and missing schemes have uniformly shown that using the new method significantly improves the power of detecting imprinted genes compared with the method using the SNP at the testing locus only. Our simulations suggest that the most efficient strategy to investigate parent-of-origin effects is to recruit one parent and as many offspring as possible under practical constraints. As a demonstration, we applied our method to a dataset from the Genetics of Lipid Lowering Drugs and Diet Network (GOLDN) to test the parent-of-origin effects of the SNPs within the PPARGC1A, MTP and FABP2 genes on diabetes-related phenotypes, and found that several SNPs in the MTP gene show parent-of-origin effects on insulin and glucose levels.

[Psoriatic arthritis : a permanent challenge for rheumatologists and patients--Part 1: epidemiology, pathogenesis and clinical course]

Psoriatic arthritis is still one of the big challenges in rheumatology due to the great variety of symptoms. Treatment frequently requires an interdisciplinary collaboration of general practitioners, dermatologists and rheumatologists who are able to recognize the onset of disease early by means of classification criteria and new imaging techniques followed by the implementation of appropriate antirheumatic treatment. During recent years new immunological pathways have been discovered leading to an increasing number of potential therapies, which increases the chance to find effective individualized treatment. However, tracking back the onset of the disease to specific causes is still a challenge which is made even more complex due to the absence of specific serum parameters.

Infliximab (Remicade) in the treatment of psoriatic arthritis

Elucidation of the cellular immunopathology and cytokine profile of psoriatic arthritis (PsA), a chronic inflammatory disease associated with psoriasis, has resulted in the development of a number of novel biologic therapies. Among these biologics, tumor necrosis factor-alpha (TNF-alpha) inhibitors have been used successfully to treat patients suffering from rheumatoid arthritis or psoriasis. The pivotal role of TNF-alpha in the pathogenesis and progression of PsA suggested that anti-TNF-alpha agents could be effective in controlling PsA. The results from two large, randomized, double-blind, placebo-controlled trials in patients with moderate to severe PsA indicated that the anti-TNF-inhibitor, infliximab, can control both the joint and skin manifestations of the disease. This review focuses on the clinical development of infliximab as a treatment for PsA. The development of other anti-TNF-alpha biologics is also discussed.

Current challenges in the genetics of psoriatic arthritis: a report from the GRAPPA 2009 annual meeting

Psoriasis and psoriatic arthritis (PsA) are heterogeneous diseases. While both have a strong genetic basis, it is strongest for PsA, where fewer investigators are studying its genetics. Over the last year the number of independent genetic loci associated with psoriasis has substantially increased, mostly due to completion of multiple genome-wide association studies (GWAS) in psoriasis. At least 2 GWAS efforts are now under way in PsA to identify novel genes in this disease; a metaanalysis of genome-wide scans and further studies must follow to examine the genetics of disease expression, epistatic interaction, and gene-environment interaction. In the long term, it is anticipated that genome-wide sequencing is likely to generate another wave of novel genes in PsA. At the annual meeting of the Group for Research and Assessment of Psoriasis and Psoriatic Arthritis (GRAPPA) in Stockholm, Sweden, in 2009, members discussed issues and challenges regarding the advancement of the genetics of PsA; results of those discussions are summarized here.

Meta-analysis of NOD2/CARD15 polymorphisms with psoriasis and psoriatic arthritis

Psoriasis and psoriatic arthritis (PsA) is a complex autoimmune disease. NOD2/CARD15 gene has been suggested to play an important role in the pathogenesis of psoriasis and PsA. This study aims to assess the association between NOD2/CARD15 polymorphisms and the susceptibility to psoriasis/PsA. A meta-analysis was performed to survey studies on the NOD2/CARD15 polymorphisms and psoriasis/PsA using comprehensive PubMed, Embase, and Web of Science citation search. A total of 9 published studies were involved. Meta-odds ratios (ORs) and 95% confidence intervals (CIs) based on fixed effects models or random effects models were depended on Cochran's Q-statistic. Potential publication bias was evaluated by Egger's linear regression test. As for R702W, the pooled ORs were 1.041 (95% CI 0.854-1.268, P = 0.693; 2,081 patients vs. 2,717 controls) for C allele and 0.886 (95% CI 0.565-1.391. P = 0.600; 1,222 patients vs. 1,818 controls) for genotype. Then for G908R, the pooled ORs were 1.042 (95% CI, 0.761-1.426, P = 0.799; 2,053 patients vs. 2,743 controls) for C allele and 0.942 (95% CI 0.708-1.254, P = 0.683; 1,226 patients vs. 1,824 controls) for the homozygous wild type. Then for Leu1007fsinsC allele polymorphism and genotype, the pooled ORs were 1.160 (95% CI, 0.893-1.507, P = 0.266; 2,279 patients vs. 3,067 controls) and 1.266 (95% CI 0.897-1.789, P = 0.180; 1,979 patients vs. 1,607 controls), respectively. No obvious publication bias was shown in the results. The association between NOD2/CARD15 polymorphisms and psoriasis/PsA was not found. Taken together, our results suggest that NOD2/CARD15 might not be a susceptibility gene for psoriasis and psoriatic arthritis.

The Genetic Basis of Spondyloarthritis: SPARTAN/IGAS 2009

A joint meeting was held in July 2009 in Houston, Texas, of members of the Spondyloarthritis Research and Therapy Network (SPARTAN), founded in 2003 to promote research, education, and treatment of ankylosing spondylitis (AS) and related forms of spondyloarthritis (SpA), and members of International Genetics of AS (IGAS), founded in 2003 to encourage and coordinate studies internationally in the genetics of AS. The general topic was the genetic basis of SpA, with presentations on the future of human genetic studies; microbes, SpA, and innate immunity; susceptibility of AS to the major histocompatibility complex (MHC) and non-MHC; and individual discussions of the genetics of psoriasis and psoriatic arthritis, uveitis, inflammatory bowel disease, and enteropathic arthritis. Summaries of those discussions are presented.

Molecular genetics of Psoriasis (Principles, technology, gene location, genetic polymorphism and gene expression)

Psoriasis is a common inflammatory skin disease with an etiology bases on both environmental and genetic factors. As is the case of many autoimmune diseases its real cause remains poorly defined. However, it is known that genetic factors contribute to disease susceptibility. The linkage analysis has been used to identify multiple loci and alleles that confer risk of the disease. Some other studies have focused upon single nucleotide polymorphisms (SNPs) for mapping of probable causal variants. Other studies, using genome-wide analytical techniques, tried to link the disease to copy number variants (CNVs) that are segments of DNA ranging in size from kilobases to megabases that vary in copy number. CNVs represent an important element of genomic polymorphism in humans and harboring dosage-sensitive genes may cause or predispose to a variety of human genetic diseases. The mechanisms giving rise to SNPs and CNVs can be considered as fundamental processes underlying gene duplications, deletions, insertions, inversions and complex combinations of rearrangements. The duplicated genes being the results of 'successful' copies are fixed and maintained in the population. Conversely, many 'unsuccessful' duplicates remain in the genome as pseudogenes. There is another form of genetic variations termed copy-neutral loss of heterozygosity (LOH) with less information about their potential impact on complex diseases. Additional studies would include associated gene expression variations with either SNPs or CNVs. Now many genetic techniques such as PCR, real time PCR, microarray and restriction fragment length analysis are available for detecting genetic polymorphisms, gene mapping and estimation of gene expression. Recently, the scientists have used these tools to define genetic signatures of disease, to understand genetic causes of disease and to characterize the effects of certain drugs on gene expression. This review highlights the principles, technology and applications on psoriasis.

Genetic variations associated with psoriasis and psoriatic arthritis found by genome-wide association

Psoriasis and psoriatic arthritis are immune disorders with a complex polygenic basis. HLA-Cw6, which lies in the major histocompatibility region on chromosome 6, is considered the major genetic determinant of psoriasis. Recent genome-wide association studies have identified new variants outside of the MHC with relevance to the immunology of psoriasis. Variants in or near genes that encode subunits of cytokines (IL12B, IL23A) or cytokine receptors (IL23R) are interesting given that the gene product of IL12B, p40, is the target of a recently approved monoclonal antibody therapy for psoriasis (ustekinumab). Association with psoriasis and psoriatic arthritis has been found in TNFAIP3 and TNFIP1, ubiquitin ligases in the NF-kappaB pathway, and IL13, a Th2 cytokine. Copy number variation of human beta-defensin and late cornified envelope genes also associate with psoriasis. Many of these genetic variations also associate with immune disorders considered psoriatic co-morbidities, including Crohn's disease and diabetes.

The role of microRNA-146a (miR-146a) and its target IL-1R-associated kinase (IRAK1) in psoriatic arthritis susceptibility

MicroRNAs have shown different expression patterns in immune diseases. The present study explores the association of miRNA-146a variant rs2910164 and of two IRAK1 (target of miR-146a) polymorphisms rs3027898 and rs1059703 with psoriasic arthritis (PsA). Twenty-nine PsA and 66 controls were enrolled in the study. To study if the statistical significant differences between patients with PsA and controls are independent to psoriasis, we expanded the study in 49 patients with ankylosing spondylitis (AS). Strong statistical significant difference was observed in IRAK1 rs3027898 polymorphism distribution between patients with PsA and controls (P = 0.003), as between patients with AS and controls (P < 0.001). Marginally significant difference was observed in distribution of IRAK1 rs1059703 genotypes between patients with PsA and controls (P = 0.058), but no difference was observed in miRNA-146a rs2910164 distribution (P = 0.394). This is the first study that addresses IRAK1 rs3027898 polymorphism association with PsA susceptibility, but further studies could help to understand the extent of the proposed association.

A new susceptibility locus for bipolar affective disorder in PAR1 on Xp22.3/Yp11.3

We present the findings of a linkage study of bipolar affective disorder (BPAD) that involve the pseudoautosomal region 1 of the human sex chromosomes. We analyzed a substantial subset of pedigrees (89 families of German and Spanish origin; 661 participants; 298 affected individuals) from the large collection of BPAD-affected families with which a genomewide linkage analysis was previously performed and where the pseudoautosomal regions were poorly covered. Nonparametric linkage (Z(lr)) scores were calculated. The highest Z(lr) scores were obtained on Xp22.3/Yp11.3 in the Spanish subsample (DXS1071; Z(lr) = 3.54, P(empirical) = 0.0009 for the broad definition of affection sttuts; Z(lr) = 2.63, P(empirical) = 0.0129 for the medium definition of affection status; Z(lr) = 2.12, P(empirical) = 0.0429 for the narrow definition of affection status). Empirical P-values are adjusted using the Bonferroni correction to account for the testing of three affection status definitions. This region has not drawn much attention in previous linkage studies of BPAD. On the basis of these results, Xp22.3/Yp11.3 should now be considered a candidate region for BPAD.

Current concepts in the pathogenesis of psoriasis

Psoriasis is a multi-factorial skin disease with a complex pathogenesis. Various factors which have been suggested to play a key role in the pathogenesis are T cells, antigen presenting cells (APC's), keratinocytes, Langerhans' cells, macrophages, natural killer cells, an array of Th1 type cytokines, certain growth factors like vascular endothelial growth factor (VEGF), keratinocyte growth factor (KGF), and others. It has been hypothesized that the disease starts with the activation of T cell by an unknown antigen, which leads to secretion of an array of cytokines by activated T cells, inflammatory cells, and keratinocytes. The characteristic lesion of psoriasis is due to the hyper-proliferation of the keratinocyte. Activated Langerhans' cells migrate from skin to lymph nodes presenting the antigen to nodal naïve T cells (cells that have not been activated by antigen previously). The T cells activated by non-antigen-dependent mechanism may, however, become antigen-specific memory cells that react with a cross-reactive auto-antigen such as keratin (molecular mimicry). The genetic background of the disease may be suggested from the fact that concordance rate is 63–73% in monozygotic twins, as compared to 17–20% in dizygotic twins. Several disease susceptibility loci have been suggested as predisposing factors, PSORS1-PSORS9.

Genetics of psoriasis and psoriatic arthritis

It is well established that psoriasis and psoriatic arthritis (PsA) have a strong genetic component. Recent advances in genetics have confirmed previous associations and new loci have been discovered. However, these loci do not fully account for the high heritability of psoriasis and PsA and therefore many genetic as well as environmental factors remain to be identified. This paper reviews the current status of genetic studies in psoriasis and PsA.

Genetic background of psoriasis

Psoriasis is a chronic inflammatory dermatosis that contributes to approximately 1-5% of all skin disorders in Saudi Arabia. The genetic basis of psoriasis is supported by family based investigations; population based epidemiological studies, association studies with human leucocyte antigens (HLAs), genome-wide linkage scans, and candidate gene studies within and outside the major histocompatibility complex. Psoriasis represents a complex disease at the cellular, genomic and genetic levels, with infiltration of many types of leukocytes into the skin, altered growth and differentiation of skin-resident cells, and altered expression of more than 1,300 genes in psoriatic lesions. It is also apparent that there is considerable overlap between the molecular pathways that are involved in psoriasis and those that lead to other inflammatory or autoimmune diseases in humans. In this review article, we describe the immune-genetic basis of psoriasis, the molecular pathways of pathogenic inflammation and the potential role of the genes that confer increased susceptibility to psoriasis.