Genetic variation at the glycosaminoglycan metabolism pathway contributes to the risk of psoriatic arthritis but not psoriasis

OBJECTIVE

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis affecting up to 30% of patients with psoriasis (Ps). To date, most of the known risk loci for PsA are shared with Ps, and identifying disease-specific variation has proven very challenging. The objective of the present study was to identify genetic variation specific for PsA.

METHODS

We performed a genome-wide association study in a cohort of 835 patients with PsA and 1558 controls from Spain. Genetic association was tested at the single marker level and at the pathway level. Meta-analysis was performed with a case-control cohort of 2847 individuals from North America. To confirm the specificity of the genetic associations with PsA, we tested the associated variation using a purely cutaneous psoriasis cohort (PsC, n=614) and a rheumatoid arthritis cohort (RA, n=1191). Using network and drug-repurposing analyses, we further investigated the potential of the PsA-specific associations to guide the development of new drugs in PsA.

RESULTS

We identified a new PsA risk single-nucleotide polymorphism at B3GNT2 locus (p=1.10e-08). At the pathway level, we found 14 genetic pathways significantly associated with PsA (p_FDR<0.05). From these, the glycosaminoglycan (GAG) metabolism pathway was confirmed to be disease-specific after comparing the PsA cohort with the cohorts of patients with PsC and RA. Finally, we identified candidate drug targets in the GAG metabolism pathway as well as new PsA indications for approved drugs.

CONCLUSION

These findings provide insights into the biological mechanisms that are specific for PsA and could contribute to develop more effective therapies.

Expert Recommendations on the Interleukin 6 Blockade in Patients with Rheumatoid Arthritis

OBJECTIVE

To draft recommendations on interleukin 6 (IL-6) blockade in rheumatoid arthritis (RA), based on best evidence and experience.

METHODS

A group of 10 experts on IL-6 blockade in RA was selected. The 2 coordinators formulated 23 questions about IL-6 blockade (indications, efficacy, safety, etc.). A systematic review was conducted to answer the questions. Using this information, inclusion and exclusion criteria were established, as were the search strategies (Medline, EMBASE and the Cochrane Library were searched). Two different reviewers selected the articles. Evidence tables were created. At the same time, European League Against Rheumatism and American College of Rheumatology abstracts were evaluated. Based on this evidence, the coordinators proposed preliminary recommendations that the experts discussed and voted on in a nominal group meeting. The level of evidence and grade of recommendation were established using the Oxford Centre for Evidence Based Medicine and the level of agreement with the Delphi technique (2 rounds). Agreement was established if at least 80% of the experts voted yes (yes/no).

RESULTS

The 8 preliminary recommendations were accepted after the Delphi process. They covered aspects such as the use of these therapies in monotherapy, in combination, in patients with refractory disease or intolerant patients, response evaluation, optimization and risk management.

CONCLUSIONS

The manuscript aims to solve frequently asked questions and aid in decision making strategies when treating RA patients with IL-6 blockade.

A deletion at ADAMTS9-MAGI1 locus is associated with psoriatic arthritis risk

OBJECTIVE

Copy number variants (CNVs) have been associated with the risk to develop multiple autoimmune diseases. Our objective was to identify CNVs associated with the risk to develop psoriatic arthritis (PsA) using a genome-wide analysis approach.

METHODS

A total of 835 patients with PsA and 1498 healthy controls were genotyped for CNVs using the Illumina HumanHap610 BeadChip genotyping platform. Genomic CNVs were characterised using CNstream analysis software and analysed for association using the χ(2) test. The most significant genomic CNV associations with PsA risk were independently tested in a validation sample of 1133 patients with PsA and 1831 healthy controls. In order to test for the specificity of the variants with PsA aetiology, we also analysed the association to a cohort of 822 patients with purely cutaneous psoriasis (PsC).

RESULTS

A total of 165 common CNVs were identified in the genome-wide analysis. We found a highly significant association of an intergenic deletion between ADAMTS9 and MAGI1 genes on chromosome 3p14.1 (p=0.00014). Using the independent patient and control cohort, we validated the association between ADAMTS9-MAGI1 deletion and PsA risk (p=0.032). Using next-generation sequencing, we characterised the 26 kb associated deletion. Finally, analysing the PsC cohort we found a lower frequency of the deletion compared with the PsA cohort (p=0.0088) and a similar frequency to that of healthy controls (p>0.3).

CONCLUSIONS

The present genome-wide scan for CNVs associated with PsA risk has identified a new deletion associated with disease risk and which is also differential from PsC risk.

Manifestaciones clínicas y alteraciones inmunológicas en pacientes con síndrome antifosfolipídico. Presentación de 112 casos

BACKGROUND AND OBJECTIVE

We decided to describe the demographic, clinical and laboratory characteristics of a series of patients with antiphospholipid syndrome (APS) (Harris criteria) and review other Spanish published series.

PATIENTS AND METHOD

We describe 112 patients with APS, 50 primary (PAPS) and 62 secondary (SAPS) -56 (90%) to systemic lupus erythematosus (SLE)-, monitorized in two referral centers in Malaga (Spain) from 1989 to 2000. All data were obtained from the medical records by means of a protocol.

RESULTS

The age was similar in both groups (42.3 [14.7] years for the whole series). Patients with SAPS had an earlier onset of the disease (29.6 [12.6] years, vs 37.0 [13.9] years in PAPS) and they had a longer evolution of the disease (143.3 [115.5] months, vs 83.5 [73.5] months in PAPS). There was a female predominance (84% and 60% in SAPS and PAPS, respectively). The prevalences of arterial (43%) and venous thrombosis (39%), fetal loss (40%), premature births (9%), anticardiolipin antibodies (88%) and lupus anticoagulant (54%) were similar in both groups. The prevalence of ANA-IFI, thrombocytopenia and autoimmune anemia was higher in SAPS.

CONCLUSIONS

Patients with PAPS and SAPS did not present any differences in the clinical manifestations and immunological disorders of the syndrome. Those patients with SAPS were younger at the beginning of the disease and there was a female predominance. Our patients were different from those included in other Spanish published series, which could be explained by selection and classification bias.

HLA class II alleles associations of anticardiolipin and anti-beta2GPI antibodies in a large series of European patients with systemic lupus erythematosus

The objective of this study was to determine the HLA class II associations of the anticardiolipin (aCL) and anti-beta2GPI (abeta2GPI) antibodies in a large series of European patients with systemic lupus erythematosus (SLE). A cohort of 577 European SLE patients was enrolled. aCL and abeta2GPI were measured by ELISA methods. Molecular typing of HLA-DRB1, DRB3, DRB4, DRB5, DQA1 and DQB1 loci was performed by the polymerase chain reaction-sequence specific oligonucleotide probes (PCR-SSOP) method. aCL of IgG, IgM and IgA isotypes were detected in 22.8%, 14% and 13.9% of patients, respectively. IgG and IgM abeta2GPI were detected in 20% of patients. aCL showed positive association with HLA DRB1*04, DRB1*0402, DRB1*0403, DRB1*07, DRB3*0301, DQA1*0201, DQA1*0301, DQB1*0302, and negative association with DQA1*0501, DRB3*0202. abeta2GPI showed positive association with DRB1*0402, DRB1*0403, DQB1*0302. DRB1*0402 carried the highest relative risk for the presence of both aCL (RR=8. 1) and abeta2GPI (RR=4.6). Our results confirm the already described associations of aCL with HLA DR4 and DR7, but also demonstrate that, among the alleles at the DRB1*04 locus, the *0402 was most represented both in aCL and in abeta2GPI positive patients. In addition, HLA class II associations of abeta2GPI are for the first time extensively examined in a large cohort of European SLE patients.