Begoña Marí-Alfonso

Identification of the PTPN22 functional variant R620W as susceptibility genetic factor for giant cell arteritis

Objective To analyse the role of the PTPN22 and CSK genes, previously associated with autoimmunity, in the predisposition and clinical phenotypes of giant cell arteritis (GCA). Methods Our study population was composed of 911 patients diagnosed with biopsy-proven GCA and 8136 unaffected controls from a Spanish discovery cohort and three additional independent replication cohorts from Germany, Norway and the UK. Two functional PTPN22 polymorphisms (rs2476601/R620W and rs33996649/R263Q) and two variants of the CSK gene (rs1378942 and rs34933034) were genotyped using predesigned TaqMan assays. Results The analysis of the discovery cohort provided evidence of association of PTPN22 rs2476601/R620W with GCA (PFDR=1.06E-04, OR=1.62, CI 95% 1.29 to 2.04). The association did not appear to follow a specific GCA subphenotype. No statistically significant differences between allele frequencies for the other PTPN22 and CSK genetic variants were evident either in the case/control or in stratified case analysis. To confirm the detected PTPN22 association, three replication cohorts were genotyped, and a consistent association between the PTPN22 rs2476601/R620W variant and GCA was evident in the overall meta-analysis (PMH=2.00E-06, OR=1.51, CI 95% 1.28 to 1.79). Conclusions Our results suggest that the PTPN22 polymorphism rs2476601/R620W plays an important role in the genetic risk to GCA.

Evidence of association of the NLRP1 gene with giant cell arteritis

Recent studies have focused attention on the involvement of NLRP1 to confer susceptibility for extended autoimmune/inflammatory disorders, being considered a common risk factor in autoimmunity.1–3 NLRP1 provides a scaffold for the assembly of the inflammasome that activates caspases 1 and 5, required for processing and activation of the proinflammatory cytokines interleukin 1β (IL-1β), IL-18 and IL-33 and promoting inflammation.4 In this study, we examined for the first time whether NLRP1 is associated with giant cell arteritis (GCA), a chronic systemic vasculitis affecting large and medium-sized arteries derived from the aorta, in particular the cranial branches of the carotid artery. GCA is the most common vasculitis in the elderly in Western countries with a female predominance.5 To investigate the possible genetic association of NLRP1 with this disease, we genotyped a single-nucleotide polymorphism (rs8182352), which has been reported to confer risk to the development of autoimmune processes in previous studies,1 ,2 in a total of 3583 individuals, comprising a discovery set from Spain (574 patients diagnosed with biopsy-proven GCA and 2366 healthy controls) and a replication set of subjects from Italy (111 biopsy-proven GCA patients and 532 controls) using a predesigned TaqMan allele discrimination assay. All individuals were of …

A Nonsynonymous Functional Variant of the ITGAM Gene Is Not Involved in Biopsy-proven Giant Cell Arteritis

Objective. To investigate whether a functional integrin alpha M (ITGAM) variant is involved in susceptibility to and clinical manifestations of giant cell arteritis (GCA). Methods. A Spanish cohort of 437 white patients with biopsy-proven GCA and 1388 healthy controls were genotyped using the TaqMan allele discrimination technology. Results. No association was observed between ITGAM rs1143679 and GCA (p = 0.80, OR 0.97). Similarly, subphenotype analyses did not yield significant differences between the case subgroups and the control set or between GCA patients with or without the main specific features of GCA. Conclusion. Our results suggest that the ITGAM rs1143679 variant does not play an important role in the pathophysiology of GCA.

OP0056 The PTPN22/CSK Signalling Pathway is Involved in Susceptibility to Develop Giant Cell Arteritis

Background The PTPN22/CSK signalling represents one of the most relevant pathways in the innate immunity, and it has been implicated in the susceptibility to develop a wide number of autoimmune diseases. Objectives To analyse the possible role of different single-nucleotide polymorphisms of the PTPN22 and CSK genes in the predisposition and clinical phenotypes of giant cell arteritis (GCA) in a large Caucasian population. Methods Our study population consisted of 623 patients diagnosed with biopsy-proven GCA and 1,729 healthy controls of Spanish Caucasian origin. Two functional PTPN22 polymorphisms (rs24746601, R620W and rs33996649, R263Q) and two variants of the CSK gene (rs1378942 and rs34933034), previously associated with autoimmunity, were genotyped using specifically designed TaqMan® assays. Results A significant association of the PTPN22 non-synonymous change rs2476601 with GCA susceptibility was yielded after the analysis of the allele frequencies (P=1.06E-04, OR= 1.62, CI 95% 1.29-2.04). No statistically significant differences between cases and controls of the rest of SNPs analysed were observed. Similarly, when patients were stratified according to specific clinical features of GCA, such as polymyalgia rheumatica (PMR), visual ischemic manifestations (VIM) or irreversible occlusive disease (IOD), only significant differences were found between the case subgroups and the control set for PTPN22 rs2476601 (P=2.26E-04, OR=1.77 CI 95% 1.30-2.40; P=1.03E-03, OR=1.82 CI 95% 1.27-2.62; P=5.47E-04, OR=2.14 CI 95% 1.38-3.33, respectively). Conclusions Our results clearly suggest that the PTPN22 polymorphism rs2476601 is associated with susceptibility to GCA. Disclosure of Interest None Declared