A Genome-wide Association Study Identifies Risk Alleles in Plasminogen and P4HA2 Associated with Giant Cell Arteritis.

Giant cell arteritis (GCA) is the most common form of vasculitis in individuals older than 50 years in Western countries. To shed light onto the genetic background influencing susceptibility for GCA, we performed a genome-wide association screening in a well-powered study cohort. After imputation, 1,844,133 genetic variants were analyzed in 2,134 case subjects and 9,125 unaffected individuals from ten independent populations of European ancestry. Our data confirmed HLA class II as the strongest associated region (independent signals: rs9268905, p = 1.94 × 10-54, per-allele OR = 1.79; and rs9275592, p = 1.14 × 10-40, OR = 2.08). Additionally, PLG and P4HA2 were identified as GCA risk genes at the genome-wide level of significance (rs4252134, p = 1.23 × 10-10, OR = 1.28; and rs128738, p = 4.60 × 10-9, OR = 1.32, respectively). Interestingly, we observed that the association peaks overlapped with different regulatory elements related to cell types and tissues involved in the pathophysiology of GCA. PLG and P4HA2 are involved in vascular remodelling and angiogenesis, suggesting a high relevance of these processes for the pathogenic mechanisms underlying this type of vasculitis.

A large-scale genetic analysis reveals a strong contribution of the HLA class II region to giant cell arteritis susceptibility.

We conducted a large-scale genetic analysis on giant cell arteritis (GCA), a polygenic immune-mediated vasculitis. A case-control cohort, comprising 1,651 case subjects with GCA and 15,306 unrelated control subjects from six different countries of European ancestry, was genotyped by the Immunochip array. We also imputed HLA data with a previously validated imputation method to perform a more comprehensive analysis of this genomic region. The strongest association signals were observed in the HLA region, with rs477515 representing the highest peak (p = 4.05 × 10(-40), OR = 1.73). A multivariate model including class II amino acids of HLA-DRß1 and HLA-DQα1 and one class I amino acid of HLA-B explained most of the HLA association with GCA, consistent with previously reported associations of classical HLA alleles like HLA-DRB1(∗)04. An omnibus test on polymorphic amino acid positions highlighted DRß1 13 (p = 4.08 × 10(-43)) and HLA-DQα1 47 (p = 4.02 × 10(-46)), 56, and 76 (both p = 1.84 × 10(-45)) as relevant positions for disease susceptibility. Outside the HLA region, the most significant loci included PTPN22 (rs2476601, p = 1.73 × 10(-6), OR = 1.38), LRRC32 (rs10160518, p = 4.39 × 10(-6), OR = 1.20), and REL (rs115674477, p = 1.10 × 10(-5), OR = 1.63). Our study provides evidence of a strong contribution of HLA class I and II molecules to susceptibility to GCA. In the non-HLA region, we confirmed a key role for the functional PTPN22 rs2476601 variant and proposed other putative risk loci for GCA involved in Th1, Th17, and Treg cell function.

Analysis of two autoimmunity genes, IRAK1 and MECP2, in giant cell arteritis.

OBJECTIVES: The Xq28 region, containing IRAK and MECP2, represent a common susceptibility locus for a high number of autoimmune diseases. Our aim in the present study was to evaluate the influence of the IRAK1 and MECP2 autoimmunity-associated genetic variants in the giant cell arteritis (GCA) susceptibility and its clinical subphenotypes. METHODS: We analysed a total of 627 female biopsy-proven GCA patients and 1,520 female healthy controls of Spanish Caucasian origin. Two polymorphisms, rs1059702 and rs17345, located at IRAK1 and MECP2, respectively, were genotyped using TaqMan® allelic discrimination assays. RESULTS: No association with any of the analysed polymorphisms was evident when genotype and allele frequencies were compared between GCA patients and controls (rs1059702: allelic p-value=0.699, OR=0.96, CI 95% 0.80-1.17; rs17435: allelic p-value=0.994, OR=1.00, CI 95% 0.84-1.19). Likewise, the subphenotype analysis yield similar negative results. CONCLUSIONS: We have assessed for the first time the possible role of IRAK1 and MECP2 autoimmune disease-associated polymorphisms in GCA. Our data suggest that IRAK1 rs1059702 and MECP2 rs17435 genetic variants do not play a significant role in GCA susceptibility or severity.

Autoimmune disease-associated CD226 gene variants are not involved in giant cell arteritis susceptibility in the Spanish population.

OBJECTIVES: CD226 genetic variants have been associated with a number of autoimmune diseases. The aim of this study was to investigate the potential implication of the CD226 loci in the susceptibility to and main clinical manifestations of giant cell arteritis (GCA). METHODS: A Spanish Caucasian cohort of 455 patients diagnosed with biopsy-proven GCA and 1414 healthy controls were included in the study. Three CD226 polymorphisms, rs727088, rs34794968 and rs763361, were genotyped using the TaqMan® allelic discrimination technology. PLINK software was used for the statistical analyses. RESULTS: No significant association between the CD226 polymorphisms and susceptibility to GCA was found (rs727088: p=0.92, OR=1.01, CI 95% 0.86-1.18; rs34794968: p=0.61, OR=1.04, CI 95% 0.89-1.22; rs763361: p=0.88, OR=0.99, CI 95% 0.84-1.16). Similarly, when patients were stratified according to the specific clinical features of GCA such as polymyalgia rheumatica, visual ischaemic manifestations or irreversible occlusive disease, no association was observed either between the case subgroups and the control set or between GCA patients with and without the specific features of the disease. Furthermore, the haplotype analysis revealed no significant association with the clinical manifestations of the disease. CONCLUSIONS: Our results show that the three CD226 polymorphisms analysed do not play a relevant role in the susceptibility to GCA and clinical manifestations of this vasculitis.

Role of the rs6822844 gene polymorphism at the IL2-IL21 region in biopsy-proven giant cell arteritis.

OBJECTIVES: To assess the influence of the interleukin (IL)2-IL21 rs6822844 G/T polymorphism in the susceptibility to biopsy-proven giant cell arteritis (GCA) and in the clinical spectrum of manifestations of this vasculitis. METHODS: Two hundred and seventy-two biopsy-proven GCA patients were included in this study. DNA from patients and matched controls (n=791) was obtained from peripheral blood. Samples were genotyped for the rs6822844 polymorphism using a predesigned TaqMan allele discrimination assay and by polymerase chain reaction amplification. RESULTS: No significant differences in the allele and genotype frequencies between biopsy-proven GCA patients and controls were observed. However, the stratification of GCA patients disclosed some differences according to gender and ischemic manifestations of the disease. In this regard, the frequency of the minor allele T was increased in males (14.8%) compared to females (8.4%) (odds ratio-OR:1.89 (95% confidence interval-CI: 1.09-3.28); p=0.02; Bonferroni adjustment p=0.12). Also, minor allele T frequency was increased in GCA patients with severe ischemic complications (12.8%) compared to those without severe ischemic complications (7.7%) (OR:1.72 (95% CI: 0.97-3.05); p=0.05; Bonferroni adjustment p=0.30), and specifically in patients with jaw claudication (13.7% versus 8.2% in those without jaw claudication; OR:1.76 (95% CI: 1.02-3.04); p=0.04; Bonferroni adjustment p=0.24). CONCLUSIONS: IL2-IL21 rs6822844 polymorphism does not appear to be a genetic risk factor for susceptibility to biopsy-proven GCA. However, this gene polymorphism may contribute to the different phenotypic expression of this vasculitis, in particular in the development of ischemic complications of the disease.

Role of the CCR5/Δ32CCR5 polymorphism in biopsy-proven giant cell arteritis.

To further explore the potential role of chemokines in giant cell arteritis (GCA), we have studied whether the CCR5/Δ32CCR5 polymorphism is implicated in the susceptibility to the disease and its specific features. A total of 352 Spanish patients with biopsy-proven GCA and 479 matched controls were assessed. DNA was obtained from peripheral blood. Samples were genotyped by PCR with specific primers spanning the 32-bp deletion region. No statistically significant difference in the Δ32CCR5 allele frequency between GCA patients (6.1%) and controls (6.8%) was observed (p = 0.58). This was also the case when the CCR5 /Δ32CCR5 genotype distribution was assessed (p = 0.49). The Δ32CCR5 allele frequency did not differ between patients with or without specific manifestations of the disease, such as polymyalgia rheumatica, visual ischemic manifestations, or irreversible occlusive disease. Hence, our results do not support a potential influence of Δ32CCR5 in the susceptibility to or clinical spectrum of GCA.

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.

Role of rs1343151 IL23R and rs3790567 IL12RB2 polymorphisms in biopsy-proven giant cell arteritis.

OBJECTIVE: To assess the potential association between the rs1343151 IL23R and the rs3790567 IL12RB2 polymorphisms and giant cell arteritis (GCA). We also studied whether these polymorphisms might influence the phenotypic expression of GCA. METHODS: In total, 357 Spanish patients with biopsy-proven GCA and 574 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the rs1343151 IL23R and the rs3790567 IL12RB2 polymorphisms using a predesigned TaqMan allele discrimination assay and by polymerase chain reaction amplification. RESULTS: Regarding the rs1343151 IL23R polymorphism, no significant differences in the genotype or allele frequencies between GCA patients and healthy controls were observed. The frequency of the minor allele A of the rs3790567 IL12RB2 variant was increased in GCA patients compared with controls (30.1% vs 25.7%, respectively; p = 0.039, OR 1.25, 95% CI 1.01-1.54). An increased frequency of subjects carrying the minor allele A (GA+AA genotypes) of the rs3790567 IL12RB2 polymorphism was found among GCA patients compared with controls (52.8% vs 44.4%; p = 0.013, OR 1.40, 95% CI 1.06-1.85). Although a higher frequency of the combination of minor alleles (A-A) in the subgroup of patients with visual ischemic complications compared with the combination of both major alleles (G-G; p = 0.029) or with the other allelic combinations (p = 0.035) was found, logistic regression analysis showed that this association was no longer significant after adjustment for potential confounding factors (A-A vs G-G: OR 2.10, 95% CI 0.88-5.04, p = 0.096). CONCLUSION: Our results support a potential influence of the rs3790567 IL12RB2 polymorphism in the pathogenesis of GCA.

Role of the C8orf13-BLK region in biopsy-proven giant cell arteritis.

Giant cell arteritis (GCA) is a complex polygenic disease in which more than one genetic locus is likely to contribute to disease susceptibility and clinical expression. In the present study, we have analyzed for first time the implication of rs13277113 and rs2736340 variants from the C8orf13-BLK gene region in the susceptibility to GCA. A total of 220 biopsy-proven GCA patients and 486 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the C8orf13-BLK region rs13277113 and rs2736340 using a predesigned TaqMan allele discrimination assay. No significant differences in the genotype distribution between GCA patients and controls for the rs13277113 and rs2736340 C8orf13-BLK gene variants were found. GCA patients were also stratified according to the presence of specific clinical features of the disease. In this regard, the allele A of the rs13277113 variant was overrepresented in patients with severe ischemic manifestations compared with patients without severe ischemic manifestations (p = 0.04; OR =1.65; 95% CI = 0.99-2.78). In conclusion, our results do not support a major implication of the C8orf13-BLK gene region in susceptibility to GCA. However, a potential implication of the rs13277113 variant in the development of severe ischemic complications may exist.

Role of BANK1 gene polymorphisms in biopsy-proven giant cell arteritis.

OBJECTIVE: Giant cell arteritis (GCA) is a complex polygenic disease in which more than 1 genetic locus is likely to contribute to disease susceptibility and clinical expression. BANK, an adaptor molecule, has been suggested to participate in the B cell antigen receptors-mediated calcium homeostasis. We assessed for the first time the implication of BANK1 functional variants in susceptibility to GCA. METHODS: Two hundred twenty-two patients with biopsy-proven GCA and 534 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for 3 putative functional BANK1 gene polymorphisms (rs17266594 T/C, rs10516487 G/A, rs3733197 G/A) using a TaqMan allele discrimination assay. RESULTS: No significant differences were observed in genotype distribution between patients with biopsy-proven GCA and controls for these 3 gene polymorphisms. A trend for a decreased risk of having GCA was observed in individuals carrying the BANK1 rs3733197 GG genotype (patients with GCA 43.9% compared to 51.6% in controls; p = 0.06, OR 0.73, 95% CI 0.53-1.02). The frequency of BANK1 rs3733197 allele G was marginally decreased in patients with biopsy-proven GCA compared to controls (p = 0.09, OR 0.82, 95% CI 0.64-1.04). Haplotype analysis of 3-single-nucleotide polymorphisms found no statistically significant differences between patients with GCA and controls. No significant differences for the BANK1 gene polymorphisms were found when patients were stratified according to specific clinical features of the disease. CONCLUSION: Our results do not support a major implication of the BANK1 locus in susceptibility to GCA.

Lack of association between IRF5 gene polymorphisms and biopsy-proven giant cell arteritis.

OBJECTIVE: Interferon (IFN) regulatory factors (IRF) are transcriptional mediators of IFN-induced signaling pathways and are involved in immune response. We have analyzed for the first time the association of 2 IRF5 gene variants in the susceptibility to giant cell arteritis (GCA). METHODS: Two hundred twenty patients with biopsy-proven GCA and 520 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the IRF5 rs2004640 and for the IRF5 CGGGG insertion/deletion polymorphism using a predesigned TaqMan allele discrimination assay and by polymerase chain reaction amplification, followed by an ABI3100 sequencer, respectively. RESULTS: A genotyping rate of 96% was achieved in this series of GCA patients. No significant differences were found in the genotype distribution between GCA patients and controls for both IRF5 gene variants. In this regard, similar genotype frequencies were found in GCA patients and controls. No significant differences were observed when GCA patients were stratified according to the presence of specific clinical features of the disease such as polymyalgia rheumatica or severe ischemic complications. CONCLUSION: Our results showed no association of IRF5 rs2004640 and CGGGG insertion/deletion polymorphisms in the susceptibility to and clinical expression of GCA.

Lack of association between TRAF1/C5 gene polymorphisms and biopsy-proven giant cell arteritis.

OBJECTIVE: A novel association with a 100-kb region on chromosome 9 that contains the tumor necrosis factor receptor-associated factor 1 (TRAF1) and C5 genes has been observed in some autoimmune rheumatic diseases, in particular in rheumatoid arthritis. We analyzed the influence of 2 single-nucleotide polymorphisms (SNP) from the TRAF1/C5 region in susceptibility to giant cell arteritis (GCA). METHODS: We assessed 220 patients with biopsy-proven GCA and 410 matched controls. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the rs10818488 and rs2900180 TRAF1/C5 gene polymorphisms by polymerase chain reaction, using a predesigned TaqMan allele discrimination assay. RESULTS: A genotyping rate of 95% was achieved in this series of GCA. No significant differences in the genotype distribution between GCA patients and controls were found for the 2 SNP. GCA patients exhibited a reduced frequency of TRAF1/C5 AA homozygosity (7.6%) compared to controls (12.7%) but the difference was only marginally significant (OR 0.58, 95% CI 0.30-1.11, p = 0.07). The frequency of minor allele T of TRAF1/C5 rs2900180 was also slightly reduced in patients (24.3%) compared to controls (27.8%) (p = 0.19). No significant differences were observed when patients were stratified according to the presence of specific clinical disease features. CONCLUSION: Our results showed no influence of rs10818488 and rs2900180 TRAF1/C5 gene polymorphisms in susceptibility to and clinical expression of GCA.

Association between IL-18 gene polymorphisms and biopsy-proven giant cell arteritis.

INTRODUCTION: The objective was to investigate the potential implication of the IL18 gene promoter polymorphisms in the susceptibility to giant-cell arteritis (GCA). METHODS: In total, 212 patients diagnosed with biopsy-proven GCA were included in this study. DNA from patients and matched controls was obtained from peripheral blood. Samples were genotyped for the IL18-137 G>C (rs187238), the IL18-607 C>A (rs1946518), and the IL18-1297 T>C (rs360719) gene polymorphisms with polymerase chain reaction, by using a predesigned TaqMan allele discrimination assay. RESULTS: No significant association between the IL18-137 G>C polymorphism and GCA was found. However, the IL18 -607 allele A was significantly increased in GCA patients compared with controls (47.8% versus 40.9% in patients and controls respectively; P = 0.02; OR, 1.32; 95% CI, 1.04 to 1.69). It was due to an increased frequency of homozygosity for the IL18 -607 A/A genotype in patients with GCA (20.4%) compared with controls (13.4%) (IL18 -607 A/A versus IL18 -607 A/C plus IL18 -607 C/C genotypes: P = 0.04; OR, 1.59; 95% CI, 1.02 to 2.46). Also, the IL18-1297 allele C was significantly increased in GCA patients (30.7%) compared with controls (23.0%) (P = 0.003; OR, 1.48; 95% CI, 1.13 to 1.95). In this regard, an increased susceptibility to GCA was observed in individuals carrying the IL18-1297 C/C or the IL18-1297 C/T genotypes compared with those carrying the IL18-1297 T/T genotype (IL18-1297 C/C plus IL18-1297 T/C versus IL18-1297 T/T genotype in GCA patients compared with controls: P = 0.005; OR, 1.61; 95% CI, 1.15 to 2.25). We also found an additive effect of the IL18 -1297 and -607 polymorphisms with TLR4 Asp299Gly polymorphism. The OR for GCA was 1.95 for combinations of genotypes with one or two risk alleles, whereas carriers of three or more risk alleles have an OR of 3.7. CONCLUSIONS: Our results show for the first time an implication of IL18 gene-promoter polymorphisms in the susceptibility to biopsy-proven GCA. In addition, an additive effect between the associated IL18 and TLR4 genetic variants was observed.

Lack of association between the rs6920220 (G/A) polymorphism of the 6q23 region and biopsy-proven giant cell arteritis.

OBJECTIVE: Recently, 2 independent studies have identified an association between several single-nucleotide polymorphisms (SNP) located in the 6q23 chromosomal region and rheumatoid arthritis (RA). Like RA, giant cell arteritis (GCA) is also a complex polygenic disease in which more than 1 genetic locus is likely to contribute to disease susceptibility and clinical expression. We analyzed the involvement of the rs6920220 (G/A) polymorphism from the 6q23/TNFAIP3 gene region in susceptibility to GCA. METHODS: Two hundred twenty patients with biopsy-proven GCA and 490 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were geno-typed for the 6q23 region rs6920220 using a TaqMan allele discrimination assay and by polymerase chain reaction (PCR) amplification. After PCR, the genotype of each sample was attributed automatically by allelic-specific fluorescence using the ABI Prism 7900 sequence detection system. RESULTS: No significant differences in the genotype distribution between patients with GCA and controls for the rs6920220 (G/A) polymorphism were found. No significant differences were observed when patients with GCA were stratified according to the presence of specific clinical features of the disease such as polymyalgia rheumatica or severe ischemic manifestations or specific visual ischemic complications. CONCLUSION: Our results show no involvement of this 6q23/TNFAIP3 gene region SNP in the susceptibility to or clinical expression of GCA.

Influence of IL2RA rs2104286 polymorphism in the risk of biopsy-proven giant cell arteritis.

OBJECTIVE: To assess the influence of the IL2RA rs2104286 A>G polymorphism on susceptibility to and clinical spectrum of manifestations of biopsy-proven giant cell arteritis (GCA). METHODS: Our study included 318 patients with biopsy-proven GCA. DNA from patients and healthy controls was obtained from peripheral blood. Samples were genotyped for the IL2RA rs2104286 A>G polymorphism using a predesigned TaqMan allele discrimination assay and by PCR amplification. RESULTS: Although GCA patients showed a higher frequency of the minor allele homozygote of IL2RA rs2104286 (GG) compared to controls (5.1% vs 2.8%, respectively; p = 0.06, odds ratio 1.84, 95% confidence interval 0.91-3.70), the allele distribution showed no significant differences between GCA patients and controls. Stratification of GCA patients according to sex or polymyalgia rheumatica, jaw claudication, visual ischemic manifestations, or other severe ischemic complications did not yield significant differences in the allele or genotype frequencies of the IL2RA rs2104286 polymorphism. CONCLUSION: IL2RA rs2104286 polymorphism does not appear to be a genetic risk factor for susceptibility to biopsy-proven GCA. Also, this polymorphism does not seem to be implicated in the clinical expression of this vasculitis.

Influence of CD40 rs1883832 polymorphism in susceptibility to and clinical manifestations of biopsy-proven giant cell arteritis.

OBJECTIVE: To assess the potential association between CD40 rs1883832 polymorphism and biopsy-proven giant cell arteritis (GCA). We also studied the influence of the polymorphism on phenotypic expression of this vasculitis, in particular the development of visual ischemic manifestations. METHODS: Three hundred five Spanish patients with biopsy-proven GCA and 788 matched controls were assessed. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the CD40 rs1883832 C/T polymorphism using a predesigned TaqMan allele discrimination assay and by polymerase chain reaction amplification. RESULTS: Patients with GCA showed a trend toward a higher frequency of the minor allele homozygote of rs1883832 (TT) compared to healthy controls (12.1% vs 8.3%, respectively; p = 0.05, OR 1.54, 95% CI 0.98-2.40). Also, a marginally significant increased frequency of the minor allele T was observed in patients with GCA who had visual ischemic manifestations (36.9%) compared to those without visual ischemic manifestations (27.7%; p = 0.04, OR 1.53, 95% CI 0.99-2.34). In this regard, patients with GCA carrying the minor allele T (either TT or TC) experienced visual ischemic manifestations more commonly than those carrying the CC genotype (58.5% vs 44.2%; p = 0.04, OR 1.78, 95% CI 0.99-3.22). CONCLUSION: Our results suggest a potential implication of the CD40 rs1883832 C/T polymorphism in susceptibility to visual ischemic manifestations in individuals with biopsy-proven GCA.

Lack of association between STAT4 gene polymorphism and biopsy-proven giant cell arteritis.

OBJECTIVE: To investigate the potential implication of the STAT4 gene polymorphism rs7574865 in the predisposition to or the clinical expression of giant cell arteritis (GCA). METHODS: A total of 212 patients diagnosed with biopsy-proven GCA were studied. DNA from patients and controls matched by age, sex, and ethnicity was obtained from peripheral blood. Samples were genotyped for STAT4 rs7574865 polymorphism. RESULTS: No statistically significant differences in the allele frequencies for the STAT4 rs7574865 polymorphism were observed between patients and controls. Although we observed an increased frequency of the T/T genotype in GCA patients (6.0%) compared to healthy controls (3.9%), this difference did not achieve statistical significance (OR 1.57, 95% CI 0.72-3.41). No statistically significant differences in allele or genotype frequencies were observed when patients were stratified according to the presence of typical disease features such as polymyalgia rheumatica, severe ischemic manifestations, and visual ischemic complications in the setting of this vasculitis. CONCLUSION: Our results do not support a major role of the STAT4 rs7574865 gene polymorphism in susceptibility to or clinical manifestations of GCA.

Association between toll-like receptor 4 gene polymorphism and biopsy-proven giant cell arteritis.

OBJECTIVE: Dendritic cells localized at the adventitia-media border of the normal medium-sized arteries play a pivotal role in the initiation of giant cell arteritis (GCA). These cells express a singular surface receptor profile, including a series of Toll-like receptors (TLR). Ligands of TLR-4 promote activation and differentiation of adventitial dendritic cells and are directly implicated in the pathogenesis of GCA. We aimed to assess the potential implication of the TLR4-(+896 A/G) gene polymorphism in the susceptibility to GCA. METHODS: A total of 210 patients diagnosed with biopsy-proven GCA and 678 matched controls were included in our study. DNA from patients and controls was obtained from peripheral blood. Samples were genotyped for the TLR4-(+896 A/G) (rs4986790) gene polymorphism by polymerase chain reaction, using a predesigned TaqMan allele discrimination assay. RESULTS: The TLR4 +896 G allele was significantly increased in biopsy-proven GCA patients compared to controls [p = 0.01; odds ratio (OR) 1.65; 95% confidence interval (CI) 1.08-2.52]. The increase was due to a significantly increased frequency of heterozygosity for the TLR4 -896 A/G genotype in the group of patients with biopsy-proven GCA compared to controls (TLR4 -896 A/G heterozygous in patients with GCA 18.1% compared to 11.4% in controls: p = 0.01; OR 1.72; 95% CI 1.10-2.69). However, no significant differences were observed when patients with GCA were stratified according to the presence of specific clinical features of the disease. CONCLUSION: Our results show for the first time an association of TLR4-(+896 A/G) gene polymorphism with susceptibility to biopsy-proven GCA.