Gerd-Marie Alenius

Common variants at TRAF3IP2 are associated with susceptibility to psoriatic arthritis and psoriasis

Psoriatic arthritis (PsA) is an inflammatory joint disease that is distinct from other chronic arthritides and which is frequently accompanied by psoriasis vulgaris (PsV) and seronegativity for rheumatoid factor. We conducted a genome-wide association study in 609 German individuals with PsA (cases) and 990 controls with replication in 6 European cohorts including a total of 5,488 individuals. We replicated PsA associations at HLA-C and IL12B and identified a new association at TRAF3IP2 (rs13190932, P = 8.56 × 10−17). TRAF3IP2 was also associated with PsV in a German cohort including 2,040 individuals (rs13190932, P = 1.95 × 10−3). Sequencing of the exons of TRAF3IP2 identified a coding variant (p.Asp10Asn, rs33980500) as the most significantly associated SNP (P = 1.13 × 10−20, odds ratio = 1.95). Functional assays showed reduced binding of this TRAF3IP2 variant to TRAF6, suggesting altered modulation of immunoregulatory signals through altered TRAF interactions as a new and shared pathway for PsA and PsV.

Antibodies against cyclic citrullinated peptide (CCP) in psoriatic patients with or without joint inflammation

Objective: To compare the prevalence of anti-CCP antibodies in psoriatic patients with and without joint inflammation, patients with early RA, and controls. Methods: Anti-CCP antibodies (cut off level 5 U/ml) were measured in 160 patients with psoriatic arthritis (PsA), 146 patients with psoriasis but no arthritic disease, 101 patients with early RA, and 102 healthy controls by ELISA. Results: 11 (7%) patients with PsA, 75 (74%) patients with early RA, 2 (2%) healthy controls (2%), and 1 (0.7%) patient with psoriasis without arthritis had anti-CCP antibodies above the cut off level. The presence of anti-CCP antibodies was not related to radiological changes and/or deformity and functional impairment in PsA. 8/11 patients with PsA and anti-CCP antibodies had a polyarthritic disease, and all fulfilled the ACR criteria for RA at 4 year follow up. Five of these 8 patients also had manifestations such as dactylitis, DIP involvement, radiological changes associated with PsA, and/or enthesitis. In multiple logistic regression analysis with polyarthritis as the dependent variable, anti-CCP antibodies and rheumatoid factor significantly distinguished RA from PsA. Conclusions: Anti-CCP antibodies were more prevalent in patients with PsA than in patients with psoriasis without arthritis, but less prevalent than in patients with early RA. Patients with PsA positive for anti-CCP antibodies more often had polyarthritic disease, but the presence of anti-CCP antibodies did not relate to radiological changes and/or deformity and functional impairment.

Early psoriatic arthritis: short symptom duration, male gender and preserved physical functioning at presentation predict favourable outcome at 5-year follow-up. Results from the Swedish Early Psoriatic Arthritis Register (SwePsA)

Objective The Swedish Early Psoriatic Arthritis Register describes the course of early psoriatic arthritis (PsA) in a real life clinical setting in Sweden. The aim of this study was to obtain information on predictors of clinical outcomes over a 5-year period with special focus on effects of gender, joint patterns, diagnostic delay and initial disease activity. Methods In six centres, patients with signs suggestive of PsA were included in the Swedish Early Psoriatic Arthritis Register within 2 years of symptom onset. CASPAR (classification for psoriatic arthritis) criteria were fulfilled by 197 patients who had passed the 5-year follow-up. Disease activity was measured by the Disease Activity Score including 28 joints (DAS28) and the Disease Activity Index for Psoriatic Arthritis (DAPSA). Remission and minimal disease activity (MDA) were used as outcome measures. Results Mean age at inclusion was 46 years, younger in male than female patients (43 vs 48 years). Mean DAS28 was 3.7 and 3.0 at inclusion and 2.8 and 2.1 at follow-up for women and men, respectively—significantly higher in women at both visits. Likewise, DAPSA scores were significantly higher in women. The degree of improvement (change in DAS28 and DAPSA) was similar. Men achieved MDA or remission (50% vs 33%, 25% vs 13%, respectively) more often, and women had significantly more polyarthritis at inclusion (49% vs 27%) and after 5 years (25% vs 15%). Axial or mono/oligoarticular disease was predominant in men. Independent predictors of MDA at the 5-year follow-up were: shorter symptom duration; greater general well-being (global visual analogue scale); and low Health Assessment Questionnaire at inclusion. Conclusions In early PsA, short delay between onset of symptoms and diagnosis, preserved function, and male gender are the most important predictors of favourable clinical outcome at the 5-year follow-up. Early recognition of PsA and active treatment may be important, particularly in women with polyarticular disease.

Diagnostic properties of metabolic perturbations in rheumatoid arthritis

IntroductionThe aim of this study was to assess the feasibility of diagnosing early rheumatoid arthritis (RA) by measuring selected metabolic biomarkers.MethodsWe compared the metabolic profile of patients with RA with that of healthy controls and patients with psoriatic arthritis (PsoA). The metabolites were measured using two different chromatography-mass spectrometry platforms, thereby giving a broad overview of serum metabolites. The metabolic profiles of patient and control groups were compared using multivariate statistical analysis. The findings were validated in a follow-up study of RA patients and healthy volunteers.ResultsRA patients were diagnosed with a sensitivity of 93% and a specificity of 70% in a validation study using detection of 52 metabolites. Patients with RA or PsoA could be distinguished with a sensitivity of 90% and a specificity of 94%. Glyceric acid, D-ribofuranose and hypoxanthine were increased in RA patients, whereas histidine, threonic acid, methionine, cholesterol, asparagine and threonine were all decreased compared with healthy controls.ConclusionsMetabolite profiling (metabolomics) is a potentially useful technique for diagnosing RA. The predictive value was without regard to the presence of antibodies against cyclic citrullinated peptides.

Dense genotyping of immune-related susceptibility loci reveals new insights into the genetics of psoriatic arthritis

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis and, despite the larger estimated heritability for PsA, the majority of genetic susceptibility loci identified to date are shared with psoriasis. Here, we present results from a case–control association study on 1,962 PsA patients and 8,923 controls using the Immunochip genotyping array. We identify eight loci passing genome-wide significance, secondary independent effects at three loci and a distinct PsA-specific variant at the IL23R locus. We report two novel loci and evidence of a novel PsA-specific association at chromosome 5q31. Imputation of classical HLA alleles, amino acids and SNPs across the MHC region highlights three independent associations to class I genes. Finally, we find an enrichment of associated variants to markers of open chromatin in CD8+ memory primary T cells. This study identifies key insights into the genetics of PsA that could begin to explain fundamental differences between psoriasis and PsA.

Variants in RUNX3 Contribute to Susceptibility to Psoriatic Arthritis, Exhibiting Further Common Ground With Ankylosing Spondylitis

OBJECTIVE Psoriatic arthritis (PsA) is a common inflammatory joint disease distinct from other chronic arthritides and frequently accompanied by psoriasis vulgaris. In a first genome-wide association study (GWAS), we were able to identify several genetic risk factors. However, even combined with previously identified factors, the genetic contribution to disease was not fully explained. Therefore, we undertook this study to investigate further 17 loci from our GWAS that did not reach genome-wide significance levels of association in the initial analysis. METHODS Twenty-one of 22 single-nucleotide polymorphisms were successfully genotyped in independent cohorts of 1,398 PsA patients and 6,389 controls and in a group of 964 German patients with psoriasis vulgaris. RESULTS Association with a RUNX3 variant, rs4649038, was replicated in independent patients and controls and resulted in a combined P value of 1.40 × 10(-8) by Cochran-Mantel-Haenszel test and an odds ratio (OR) of 1.24 (95% confidence interval [95% CI] 1.15-1.33). Further analyses based on linkage disequilibrium (LD) at RUNX3 refined the most significant association to an LD block located in the first intron of one isoform. Weaker evidence for association was detected in German patients with psoriasis vulgaris (P = 5.89 × 10(-2) ; OR 1.13 [95% CI 1.00-1.28]), indicating a role in the skin manifestations of psoriasis. CONCLUSION Our analyses identified variants in RUNX3 as susceptibility factors for PsA. RUNX3 has already been implicated in susceptibility to ankylosing spondylitis, another spondyloarthritis, although its risk allele is independent from the one for PsA. RUNX-3 is involved in CD8+ T lymphocyte differentiation and is therefore a good candidate for involvement in PsA and psoriasis vulgaris as T cell-mediated diseases.

Renal abnormalities in a population of patients with psoriatic arthritis

OBJECTIVE To investigate the prevalence of and to identify predictive factors for renal abnormalities in patients with psoriatic arthritis (PsA). METHODS 73 patients with PsA were consecutively examined by laboratory analyses and clinically for joint manifestations. Renal function was estimated by creatinine clearance and urinary albumin. RESULTS 17 (23.3%) of the patients had renal abnormalities as defined by creatinine clearance below the lower cut off of normal distribution (mean - 2 SD) and/or urinary excretion of albumin more than 25 mg/24 h. These patients were significantly older at the time of the study, older at joint disease onset, had longer skin disease duration, increased serum levels of beta2-microglobulin, and higher incidence of increased ESR and/or CRP levels. Increased ESR/CRP levels had significantly predictive value in multivariate analysis. CONCLUSIONS In this study subclinical renal abnormalities was a prevalent finding. Predictive factor was inflammatory activity measured by laboratory variables. There were no predisposing effects of NSAID or DMARD therapy.Objective. To investigate the prevalence of and to identify predictive factors for renal abnormalities in patients with psoriatic arthritis (PsA). Methods. 73 patients with PsA were consecutively examined by laboratory analyses and clinically for joint manifestations. Renal function was estimated by creatinine clearance and urinary albumin. Results. 17 (23.3%) of the patients had renal abnormalities as defined by creatinine clearance below the lower cut off of normal distribution (mean - 2 SD) and/or urinary excretion of albumin more than 25 mg/24 h. These patients were significantly older at the time of the study, older at joint disease onset, had longer skin disease duration, increased serum levels of g 2-microglobulin, and higher incidence of increased ESR and/or CRP levels. Increased ESR/CRP levels had significantly predictive value in multivariate analysis. Conclusion. In this study subclinical renal abnormalities was a prevalent finding. Predictive factor was inflammatory activity measured by laboratory variables. There were no predisposing effects of NSAID or DMARD therapy.

Disease manifestations and HLA antigens in psoriatic arthritis in northern Sweden

Abstract: The aim of this study was to identify potential markers of aggressive joint manifestations and HLA associations in patients with psoriatic arthritis (PsA) in northern Sweden. Patients with PsA were examined clinically, with laboratory tests and radiologically. The classification of the disease was based on peripheral and/or axial engagement. HLA B17, B37 and B62 were significantly increased in PsA patients. Univariate analyses suggest that the HLA antigens B37, B62 and some clinical variables were associated with disease course. However, in multivariate analyses distal interphalangeal joint affliction and polyarticular manifestations were the only variables remaining significantly associated with irreversible joint destruction or deformity. There were no significant effects of HLA antigens. In this cross-sectional study, clinical manifestations were more reliable predictors of aggressive joint damage than were specific HLA antigens. However, HLA antigens seemed to modify the expression of the joint disease rather than being involved in joint disease susceptibility.

PTPN22 is associated with susceptibility to psoriatic arthritis but not psoriasis: evidence for a further PsA-specific risk locus

Objectives Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis; it has a higher estimated genetic component than psoriasis alone, however most genetic susceptibility loci identified for PsA to date are also shared with psoriasis. Here we attempt to validate novel single nucleotide polymorphisms selected from our recent PsA Immunochip study and determine specificity to PsA. Methods A total of 15 single nucleotide polymorphisms were selected (PImmunochip <1×10−4) for validation genotyping in 1177 cases and 2155 controls using TaqMan. Meta-analysis of Immunochip and validation data sets consisted of 3139 PsA cases and 11 078 controls. Novel PsA susceptibility loci were compared with data from two large psoriasis studies (WTCCC2 and Immunochip) to determine PsA specificity. Results We found genome-wide significant association to rs2476601, mapping to PTPN22 (p=1.49×10−9, OR=1.32), but no evidence for association in the psoriasis cohort (p=0.34) and the effect estimates were significantly different between PsA and psoriasis (p=3.2×10−4). Additionally, we found genome-wide significant association to the previously reported psoriasis risk loci; NOS2 (rs4795067, p=5.27×10−9). Conclusions For the first time, we report genome-wide significant association of PTPN22 (rs2476601) to PsA susceptibility, but no evidence for association to psoriasis.

S-Calprotectin (S100A8/S100A9): A Potential Marker of Inflammation in Patients with Psoriatic Arthritis

Objective. To analyse levels of S100A8/S100A9 (calprotectin) and selected cytokines, in blood, in patients with psoriatic arthritis (PsA). Methods. Sixty-five patients with PsA were examined for clinical manifestations and laboratory measurements of S-calprotectin, ESR, hs-CRP, and selected cytokines. Thirty-two patients had mono-/oligoarthritis and 33 had polyarthritis. S-calprotectin, hs-CRP, and cytokines were measured using ELISA, immunoturbidimetry, and multiplex technology (Bio-Plex). Patients with PsA were compared with 31 healthy controls. Results. S-calprotectin and hs-CRP levels were significantly higher in patients with PsA compared with controls (P < 0.001 and P < 0.001, resp.). Patients suffering a polyarthritic disease pattern presented with significantly higher levels of S-calprotectin compared with controls and patients with mono-/oligoarthritis (P < 0.001 and P = 0.017, resp.). The levels of S-calprotectin correlated with hs-CRP (P < 0.001; r s = 0.441), swollen joint count (P = 0.002, r s = 0.397), and CXCL10 (P = 0.046, r s = 0.678) but not with any of the other cytokines evaluated. In multiple logistic regression analysis, S-calprotectin was the only variable significantly associated with psoriatic arthritis (P = 0.002, OR = 1.006, 95% CI = 1.002–1.010). Conclusion. S-calprotectin and hs-CRP levels were significantly higher in patients with PsA. A polyarthritic disease pattern showed higher levels of S-calprotectin than mono-/oligoarthritis. S-calprotectin is considered a potential marker of disease activity in patients with PsA.