Evidence for linkage of the HLA-B locus in Behçet's disease, obtained using the transmission disequilibrium test

Advances in pathogenesis and treatment of ocular involvement in Behcet's disease

Behcet's disease (BD) is a chronic multi-systemic disease characterized by relapsing-remitting oral ulcers, genital ulcers, ocular inflammatory involvements, and numerous other systemic features. Ocular involvements are quite common in BD and may cause severe tissue damage and potentially blindness. Even though the pathogenesis of BD remains ambiguous, growing evidences have shown that genetic factors, environmental triggers and immunological abnormalities play significant roles in its development and progression. Novel biotherapies targeting IFN-γ, TNF-α and interleukins have been used in recent years. In this review, we mainly pay attention to the ocular involvement of BD, and discuss the current understanding of mechanisms and advances in therapeutic approaches, especially novel biologics. Finally, we discuss the management in patients with pregnancy.

Behçet Syndrome

Behçet's syndrome is a systemic vasculitis affecting arteries and veins of all sizes as well as recurrent oral, genital, and intestinal ulcers, skin lesions, predominantly posterior uveitis, and parenchymal brain lesions. These can be present in various combinations and sequences over time and diagnosis is made by recognizing the manifestations, as there are no diagnostic biomarkers or genetic tests. Treatment modalities include immunomodulatory agents, immunosuppressives and biologics, tailored according to prognostic factors, disease activity, severity, and patients' preferences.

A comprehensive overview on the genetics of Behçet's disease

Behçet's disease (BD) is a systemic and inflammatory disease, characterized mainly by recurrent oral and genital ulcers, eye involvement, and skin lesions. Although the exact etiopathogenesis of BD remains unrevealed, a bulk of studies have implicated the genetic contributing factors as critical players in disease predisposition. In countries along the Silk Road, human leukocyte antigen (HLA)-B51 has been reported as the strongest genetically associated factor for BD. Genome-wide association studies, local genetic polymorphism studies, and meta-analysis of combined data from Turkish, Iranian, and Japanese populations have also identified new genetic associations with BD. Among these, other HLA alleles such as HLA-B*15, HLA-B*27, HLA-B*57, and HLA-A*26 have been found as independent risk factors for BD, whereas HLA-B*49 and HLA-A*03 are independent protective alleles for BD. Moreover, other genes have also reached the genome-wide significance level of association with BD susceptibility, including IL10, IL23R-IL12RB2, IL12A, CCR1-CCR3, STAT4, TNFAIP3, ERAP1, KLRC4, and FUT2. Also, several rare nonsynonymous variants in TLR4, IL23R, NOD2, and MEFV genes have been reported to be involved in BD pathogenesis. According to genetic determinants in the loci outside the MHC region that are contributed to the host defense, immunity, and inflammation pathways, it is suggested that immune responses to the pathogen as an important environmental factor and mucosal immunity contribute to BD susceptibility.

Behçet disease (BD) and BD-like clinical phenotypes: NF-κB pathway in mucosal ulcerating diseases

Behçet's disease (BD) is a heterogeneous multi-organ disorder in search of a unified pathophysiological theory and classification. The disease frequently has overlapping features resembling other disease clusters, such as vasculitides, spondyloarthritides and thrombophilias with similar genetic risk variants, namely HLA-B*51, ERAP1, IL-10, IL-23R. Many of the BD manifestations, such as unprovoked recurrent episodes of inflammation and increased expression of IL-1, IL-6 and TNFα, overlap with those of the hereditary monogenic autoinflammatory syndromes, positioning BD at the crossroads between autoimmune and autoinflammatory syndromes. BD-like disease associates with various inborn errors of immunity, including familial Mediterranean fever, conditions related to dysregulated NF-κB activation (eg TNFAIP3, NFKB1, OTULIN, RELA, IKBKG) and either constitutional trisomy 8 or acquired trisomy 8 in myelodysplastic syndromes. We review here the recent advances in the immunopathology of BD, BD-like diseases and the NF-κB pathway suggesting new elements in the elusive BD etiopathogenesis.

Association of HLA-B27 and Behcet's disease: a systematic review and meta-analysis

Background

To calculate the genetic impact of the “HLA-B27” allele on the risk of Behcet’s disease (BD) progression using a systematic review and meta-analysis on case control papers.

Methods

A systematic review search was conducted on the MeSH keywords of Behcet’s disease, HLAB27 and B27 in PubMed, Scopus, ProQuest, EMBASE, SID, Magiran, IranDoc and IranMedex databases from 1975 to Aug 2017. Data underwent meta-analysis (random effect model) in CMA2 software. Pooled odds ratios with 95% confidence intervals were calculated for each study. The heterogeneity of the articles was measured using the I² index.

Results

Twenty two articles met the inclusion criteria for 3939 cases and 6077 controls. The pooled OR of “HLA-B27” in BD patients compared with controls was [1.55 (CI 95% 1.01–2.38), P = 0.04]. The OR differ among different countries or geographical areas, focus on domination the European countries. Quality of studies was moderate and heterogeneity was relatively high (I² = 66.9%).

Conclusions

There is a significant correlation between HLA-B27 and Behcet’s Disease, but it was weak. Environmental and genetic factors might determine which the “HLA-B27” alleles manifest Behcet’s disease progression. Future researches is required to perform about what factors can do to positively and separately influence Behcet’s disease.

AIF-1 gene does not confer susceptibility to Behçet's disease: Analysis of extended haplotypes in Sardinian population

BACKGROUND

Behçet's disease (BD) is a polygenic immune-mediated disorder characterized by a close association with the HLA-B*51 allele. The HLA region has a strong linkage disequilibrium (LD) and carries several genetic variants (e.g. MIC-A, TNF-α genes) identified as associated to BD because of their LD with HLA-B*51. In fact, the HLA-B*51 is inherited as part of extended HLA haplotypes which are well preserved in patients with BD. Sardinian population is highly differentiated from other Mediterranean populations because of a distinctive genetic structure with very highly preserved HLA haplotypes.

PATIENTS AND METHODS

In order to identify other genes of susceptibility to BD within the HLA region we investigated the distribution of human Allograft Inflammatory Factor-1 (AIF-1) gene variants among BD patients and healthy controls from Sardinia. Six (rs2736182; rs2259571; rs2269475; rs2857597; rs13195276; rs4711274) AIF-1 single nucleotide polymorphisms (SNPs) and related extended haplotypes have been investigated as well as their LD within the HLA region and with HLA-B*51. Overall, 64 BD patients, 43 HLA-B*51 positive healthy controls (HC) and 70 random HC were enrolled in the study.

RESULTS

HLA-B*51 was the only allele with significantly higher frequency (pc = 0.0021) in BD patients (40.6%) than in HC (9.8%). The rs2259571T AIF-1 variant had a significantly reduced phenotypic, but not allelic frequency in BD patients (72.1%; pc = 0.014) compared to healthy population (91.3%). That was likely due to the LD between HLA-B*51 and rs2259571G (pc = 9E-5), even though the rs2259571G distribution did not significantly differ between BD patients and HC.

CONCLUSION

No significant difference in distribution of AIF-1 SNPs haplotypes was observed between BD patients and HC and between HLA-B*51 positive BD patients and HLA-B*51 positive HC. Taken together, these results suggest that AIF-1 gene is not associated with susceptibility to BD in Sardinia.

Differential clinical presentation of Adamantiades-Behçet's disease in non-endemic and endemic areas: retrospective data from a Middle-European cohort study

OBJECTIVES

To assess demographical and clinical data in a Middle-European cohort of patients with Adamantiades-Behçet's disease (ABD), together with the use of medication in adherence to international guidelines.

METHODS

In a retrospective cohort study, in- and outpatients of an Austrian secondary and tertiary university hospital center were analyzed independent from the medical discipline involved. After ethics approval, screening for ABD-patients in the clinical information system resulted in 1821 documents from 1997 to 2016. Patients fulfilling the International Criteria for Behçet's Disease were included, and ABD symptoms and signs together with medical interventions for immunosuppression, anticoagulation and pain management were identified by individual chart reviews and evaluated for conformity with international recommendations.

RESULTS

A total of 76 ABD patients were identified with 39.1% Austrian and 37.0% Turkish origin. Genital aphthae and skin manifestations were more frequent, neurological, gastrointestinal and vascular manifestations less frequent in ABD patients of Turkish origin living in Austria compared to those living in Turkey (each P < 0.05). The male-to-female ratio averaged 0.86 (0.39 in patients with Austrian and 1.43 with Turkish backgrounds), and was 3.3 in patients with venous manifestations. Out of 174 medical interventions, 55.2% fully matched the European League Against Rheumatism recommendations of 2008, and 93.7% were considered at least as equal to the recommendations. Indications for tumor necrosis factor inhibition were in line with the 2007 Sfikakis recommendations.

CONCLUSIONS

In this Middle-European ABD cohort clinical presentations between patients of Austrian and Turkish origin do not strongly vary, whereas Turkish patients from the non-endemic Innsbruck cohort present differently compared to patients living in Turkey. The role of such cohort analyses will increase, from the epidemiological as well as the management perspective.

Association study of rs924080 and rs11209032 polymorphisms of IL23R-IL12RB2 in a Northern Chinese Han population with Behcet's disease

OBJECTIVES

Two genome-wide association studies (GWAS) have identified the IL-23 receptor- IL-12 receptor β2 (IL23R-IL12RB2) as the susceptibility genetic region in Turkish and Japanese population with Behçet's disease (BD). We investigated the association of this region with BD in a Northern Chinese Han population.

METHODS

A total of 407 patients with BD and 421 healthy controls were genotyped for single nucleotide polymorphisms (SNPs) rs924080 and rs11209032 using the Sequenom MassArray system.

RESULTS

Statistically significant associations with BD were detected at two SNPs namely, rs924080 and rs11209032, both, by allele analysis (OR=1.58, 95% CI=1.25-2.00, P_c=2.52×10^-4, and OR=1.45, 95% CI=1.19-1.76, P_c=3.46×10^-4, respectively), and genotype analysis (P_c=1.22×10^-3andP_c=1.77×10^-3, respectively). Significant differences were observed in the genotype frequency distribution for these SNPs under the additive, dominant and recessive models (all P_c<0.05). The haplotypes (AT and GC) formed by the two SNPs were associated with BD (all permutation P<0.05). A meta-analysis also appeared to support the association of the two SNPs with BD.

CONCLUSION

SNPs (rs924080 and rs11209032) of the IL23R-IL12RB2 region were found to be associated with BD in a Northern Chinese Han population.

The immunogenetics of Behçet's disease: A comprehensive review

Behçet's disease is a chronic multisystem inflammatory disorder characterized mainly by recurrent oral ulcers, ocular involvement, genital ulcers, and skin lesions, presenting with remissions and exacerbations. It is thought that both environmental and genetic factors contribute to its onset and development. Although the etiology of Behçet's disease remains unclear, recent immunogenetic findings are providing clues to its pathogenesis. In addition to the positive association of HLA-B*51, which was identified more than four decades ago, and which has since been confirmed in multiple populations, recent studies report additional independent associations in the major histocompatibility complex class I region. HLA-B*15, -B*27, -B*57, and -A*26 are independent risk factors for Behçet's disease, while HLA-B*49 and -A*03 are independent class I alleles that are protective for Behçet's disease. Genome-wide association studies have identified associations with genome-wide significance (P < 5 × 10(-8)) in the IL23R-IL12RB2, IL10, STAT4, CCR1-CCR3, KLRC4, ERAP1, TNFAIP3, and FUT2 loci. In addition, targeted next-generation sequencing has revealed the involvement of rare nonsynonymous variants of IL23R, TLR4, NOD2, and MEFV in Behçet's disease pathogenesis. Significant differences in gene function or mRNA expression associated with the risk alleles of the disease susceptibility loci suggest which genes in a disease-associated locus influence disease pathogenesis. These genes encompass both innate and adaptive immunity and confirm the importance of the predominant polarization towards helper T cell (Th) 1 versus Th2 cells, and the involvement of Th17 cells. In addition, epistasis observed between HLA-B*51 and the risk coding haplotype of the endoplasmic reticulum-associated protease, ERAP1, provides a clue that an HLA class I-peptide presentation-based mechanism contributes to this complex disease.

Cogan and Behcet syndromes

Cogan and Behcet syndromes are considered large vessel vasculitides. Both are rare diseases, with varied clinical manifestations affecting multiple organ systems. Although both have hallmark symptoms (ocular and vestibuloauditory inflammation in Cogan syndrome and aphthous ulcers in Behcet syndrome), neither has confirmatory diagnostic testing. Delayed diagnosis can result in poor outcomes. In both syndromes, large vessel arterial inflammation may result in severe morbidity and mortality. Treatment strategies in both syndromes vary based on organ system involvement and severity of manifestations. In this article, the epidemiology, proposed pathogenesis, manifestations, and the most current treatment paradigms for these syndromes are reviewed.

MATHEMATICAL MODELING OF BEHÇET'S DISEASE: A DYNAMICAL SYSTEMS APPROACH

Behçet's Disease (BD) is a multi-systemic, auto-inflammatory disorder that is characterized by recurrent episodes of inflammatory manifestations affecting skin, mucosa, eyes, blood vessels, joints and several other organs. BD is classified as a multifactorial disease with an important contribution of genetics. Genetic studies suggest that there is a strong association of BD with a Class I major histocompatibility complex antigen, named HLA-B*51, along with several other weaker associations with genes encoding proteins involved in inflammation. However, pathogenic mechanisms associated with these genetic variations and their interactions with the environment have not been elucidated yet. In this paper, we present a mathematical model for BD based on a dynamical systems perspective that captures especially the relapsing nature of the disease. We propose a disease progression mechanism and construct a model, in the form of coupled ordinary differential equations (ODEs), which reveals the occurrence pattern of the disease in the population. According to our model, the disease has three distinct modes describing different phenotypes of people carrying HLA-B*51 tissue antigen, namely, the Healthy Carrier, the Potential Patient and the Active Patient. We herein present an exemplary mathematical model for BD, for the first time in the literature, that concisely captures the actions of many cell types together with genetic and environmental effects. The proposed model provides insight into this complex inflammatory disease which may lead to identification of new tools for its treatment and prevention.

Behçet syndrome: from pathogenesis to novel therapies

Behçet syndrome is a chronic disease hallmarked by inflammation of the blood vessels that is related to an autoimmune reaction caused by inherited susceptibility due to specific genes and environmental factors, probably components of infectious microorganisms, which turn on or get going the disease in genetically susceptible subjects. The more common clinical expression of the disease is represented by a triple-symptom complex of recurrent oral aphthous ulcers, genital ulcers, and uveitis, sometimes associated with inflammatory arthritis, phlebitis, iritis, as well as inflammation of the digestive tract, brain, and spinal cord. The treatment strategies used to manage the manifestations of Behçet syndrome have gradually progressed, and a number of new therapeutic resources have been implemented in recent years, allowing better control of pathogenic mechanisms, reducing symptoms and suffering, and ameliorating patient's outcome.

Genetics of Behçet's disease: lessons learned from genomewide association studies

PURPOSE OF REVIEW

Behçet's disease is a complex disease, and genetic susceptibility plays a critical role. This review aimed to discuss the recent genomewide association study (GWAS) findings and their implications to the pathogenesis of Behçet's disease.

RECENT FINDINGS

GWAS data confirmed the major role of HLA-B51 in Behçet's disease susceptibility, and the discovery of epistatic interactions between HLA-B51 and ERAP1 variants provided some hints about its possible pathogenic mechanisms. Investigation of human leukocyte antigen (HLA) Class I region showed weaker but independent associations around HLA-A and HLA-C regions. Genomewide studies also established associations with IL10, IL23R, CCR1, STAT4, KLRC4, GIMAP2/GIMAP4, and UBAC2 genes in Behçet's disease patients of different ethnicities. Deep resequencing of targeted genes identified additional associations with rare variants in TLR4, MEFV, and NOD2 genes.

SUMMARY

GWAS data established a major step forward by providing insights into the underlying mechanisms in Behçet's disease with the discovery of new susceptibility genes. These variations may implicate defects in the sensing and processing of microbial and endogenous danger signals as well as in the regulation of innate and adaptive immune responses in Behçet's disease. Association findings with HLA Class I antigens as well as IL23R, ERAP1, IL10, and MEFV genes also suggest shared inflammatory pathways with spondyloarthropathies.

Polymorphisms of interleukin 6 and interleukin 10 in Egyptian people with Behcet's disease

Cytokines play critical roles in the pathogenesis of Behçet's disease (BD). They mediated many of the effectors and regulatory functions of immune and inflammatory responses. Many studies have linked Interleukin-6 (IL-6) and Interleukin-10 (IL-10) pathologically to BD. Thus, this study aimed to investigate the associations between IL-6 and IL-10 promoter single-nucleotide polymorphisms (SNPs) and the susceptibility to BD and their implication on plasma levels. We genotyped IL-6 -174 G/C (rs1800795) using Mutagenically Separated Polymerase Chain Reaction PCR (MS-PCR) and IL-10 -1082 G/A (rs1800896) and -819 C/T (rs1800871) using Sequence Specific Primer PCR (SSP-PCR) in 87 Egyptian patients and 97 controls. The plasma levels of IL-6 and IL-10 were measured using Enzyme-linked Immunosorbent Assay (ELISA). Significant increase in the frequency of -1082 GG genotype (P<0.05, OR=2.25, 95%CI=1.03-4.91) and significant decrease in the frequency of -1082 GA genotype (P<0.05, OR=0.53, 95%CI=0.29-0.96) was demonstrated in BD patients compare to controls. Patients with genital ulcer had significantly lower frequency of -1082 GG (P<0.05, OR 0.2, 95% CI=0.04-0.99) and G allele (P<0.05, OR=0.28, 95%CI=0.08-0.93), while patients with ocular manifestations had significantly higher frequency of -1082 G allele (P<0.01, OR=2.28, 95%CI=1.19-4.36). BD patients had significantly higher level of IL-6 (P<0.001) and significantly lower level of IL-10 (P<0.001) compared to controls. The changes in the level of cytokines were independent of any genotype of IL-6 or any genotype/haplotype of IL-10. Patients with active disease state had significantly higher level of IL-6 compared to patients in remission (P<0.05). In conclusion, our preliminary study indicates that the polymorphism at IL-10 -1082 G/A may play a role in BD susceptibility. The significant increase in IL-6 level and the significant decrease in IL-10 level in BD patients were independent of any particular genotype in IL-6 or any particular genotype/haplotype in IL-10.

Association of Rho-kinase 1 (ROCK1) gene polymorphisms with Behçet's disease

BACKGROUND AND OBJECTIVE

Behçet's disease (BD) is a chronic inflammatory vasculitis presenting with flares and silent periods usually between 15 and 40 years of age. The aim of this study was to evaluate the possible association between Rho-kinase 1 (ROCK1) gene polymorphisms and patients with BD in a Turkish population.

METHODS

A total of 192 BD patients and 255 healthy controls of similar age and sex were enrolled in this study. Polymorphisms were analyzed in genomic DNA using a BioMark HD dynamic array system.

RESULTS

In the presence of CC genotype for rs73963110, CT genotype for rs111874856 (Val355Ile), and TC genotype for rs112130712 (Lys1054Arg) polymorphisms, the risk of BD increased 12.13-, 15.05-, and 16.28-fold, respectively (p < 0.0001). There was a lower frequency of the GA genotype of the rs112108028 (Pro1164Leu) polymorphisms in BD (10.3 %) compared with controls (39.7 %; p < 0.0001). Marked associations between these polymorphisms and the manifestations of BD were recorded.

CONCLUSION

This is the first study to show that ROCK1 gene polymorphisms may have a significant impact on susceptibility to BD.

[Epidemiology of Behçet's disease]

With more than 30 published prevalence estimates for Behçet's disease (BD), covering many different regions worldwide, the prevalence of BD is quite well described. Even though the interpretation of these data is complicated by between-study differences in methodology, which may substantially influence the results, these data suggest large geographic variations in frequency of BD, with prevalence rates of 20-420/100,000 inhabitants for Turkey, 2.1-19.5 for other Asian countries, 1.5-15.9 for southern Europe and 0.3-4.9 for northern Europe. Additional epidemiological studies or case series from North and South America, the Caribbean Islands, and individuals of sub-Saharan ancestry further suggest that the geographic distribution of BD is much wider than the boundaries of the ancient Silk Road. The few available incidence rates prevent from making strong inferences as to whether the frequency of BD has changed over time. Recent population-based studies of immigrants or migrant populations consistently indicate that migrants from areas of high BD prevalence remain at high risk for BD, which may even be close to the prevalence observed in their countries of origin. Genetic factors, which are not detailed in this review, seem to play a preponderant role in BD development, although they cannot explain the wide between-country disparities in BD prevalence. However, environmental risk factors, including infectious and non-infectious causes, remain poorly investigated and have not yet produced solid hints.

Neuro-Behçet syndrome

Behçet syndrome (BS) is an idiopathic chronic relapsing multisystem vascular-inflammatory disease of unknown origin. As the disease affects many organs and systems and shows a wide range of clinical manifestations and presentations, it is prefereable to call Behçet's a syndrome (BS) rather than a disease. Nervous system involvement, known as "neuro-BS" (NBS), is seen in about 5-10% of all cases. Clinical and imaging evidence suggests that primary neurologic involvement in BS may be subclassified into two major forms: the first, which is seen in the majority of patients, may be characterized as a vascular-inflammatory central nervous system disease with focal or multifocal parenchymal involvement, mostly presenting with a subacute brainstem syndrome and hemiparesis (intra-axial NBS); the other, which has few symptoms and a better neurologic prognosis, may be caused by isolated cerebral venous sinus thrombosis and intracranial hypertension (extra-axial NBS), occurring in 10-20% of the cases. These two types are rarely seen in the same individual, and their pathogenesis is likely to be different. Isolated behavioral syndromes and peripheral nervous system involvement are rare, whereas a vascular type headache is relatively common and independent from neurologic involvement. Neurologic complications secondary to systemic involvement of BS, as well as neurologic complications related to BS treatments are considered as secondary neurologic involvement of the syndrome. The core histopathologic phenomenon seems to be a vasculitic involvement in some cases, and low-grade chronic nonspecific inflammation in others. As the neurologic involvement in this syndrome is so heterogeneous, it is difficult to predict its course and prognosis, and its response to treatment. Currently, treatment options for NBS are limited to attack therapies with high-dose intravenous methylprednisolone followed by a prolonged oral taper, symptomatic management, and generally the use of azathioprine, cyclophosphamide, interferon-α and anti-TNF agents for long-term preventive treatment, although there no evidence for their efficacy.

IL10 polymorphisms associated with Behçet's disease in Chinese Han

OBJECTIVE

IL-10 is a potent anti-inflammatory cytokine that plays important roles in the pathogenesis of Behçet's disease (BD). Two genome-wide association studies have identified IL10 as a potential risk factor for BD. Here, we investigated the association between IL10 polymorphisms and BD in Chinese Han.

METHODS

407 BD patients and 679 healthy controls were enrolled, and genotyped by Sequenom MassArray system (Sequenom iPLEX assay, San Diego, CA).

RESULTS

The frequency of risk allele of rs1800871 was notably higher in BD patients than in controls (71.9% vs. 66.2%, OR: 1.30, 95%CI: 1.08-1.58, pc=0.024). Similarly, rs1518111, which showed strong linkage disequilibrium (r(2)=1) with allele rs1800871, was also associated with BD (pc=0.026). Rs3021094 was in association with BD in a dominant model (pc=0.035), and the haplotype (GACC) formed by rs1518111, rs3021094, rs3790622, and rs1800871 was associated with BD (pc=0.023). Results obtained from meta-analysis combined with our data showed that rs1800871 and rs1518111 were associated with BD.

CONCLUSION

IL10 may be the susceptibility gene for BD in Chinese Han population.

Genetic variants in the JAK1 gene confer higher risk of Behcet's disease with ocular involvement in Han Chinese

Recent surveys have identified SLC22A4, SLC22A5, RUNX1, JAK1 as susceptibility genes for various immune-related diseases. An association study was performed in 738 Behcet's patients with ocular involvement and 1,873 controls using the iPLEX system method. The first-stage study for 30 SNPs showed that SNPs rs2780815, rs310241, rs3790532 in JAK1 were associated with Behcet's disease in Han Chinese (Pc(Bonferroni correction) = 0.022-7.7 × 10(-3)). The G allele and AA genotype of SNP rs2834643 in RUNX1 (Pc = 0.041-1.75 × 10(-3)), but none of the other SNPs, were associated with Behcet's disease. Haplotype analysis for the SLC22A4, SLC22A5 genes showed an increased tendency for AGTCTGCCGC frequency in patients compared with controls; however, the significance was lost after Bonferroni correction (P = 0.004, Pc > 0.05). Subsequently, we further replicated the significantly associated SNPs using another independent cohort. Replication and combining studies showed that three SNPs rs2780815, rs310241, rs3790532 in JAK1, but not SNP rs2834643 in RUNX1, were consistently associated with Behcet's disease (replication: Pc = 0.012-9.60 × 10(-4); combining: Pc = 0.030-1.90 × 10(-4)). SNPs rs2780815, rs310241, rs3790532 were estimated to confer a population attributable risk of 35.0, 28.0, 27.0 %, respectively. We found a strong association between HLA-B51 with Behcet's disease in Chinese Han population (P = 1.35 × 10(-73); OR = 5.15; 95 % CI 4.28-6.19). GMDR analysis showed that no gene-gene interaction was detectable between JAK1 and HLA-B51. Logistic analysis indicated that the JAK1 gene was an independent risk factor for Behcet's disease (P > 0.05). Real-time PCR analysis showed that no difference on the expression of JAK1 in PBMCs or LPS-stimulated PBMCs between individuals with the different rs1762780815 genotypes studied (P > 0.05). In conclusion, this study suggests that JAK1, but not SLC22A4, SLC22A5 and RUNX1, contributes to the genetic susceptibility to Behcet's disease with ocular involvement.

Identification of a susceptibility locus in STAT4 for Behçet's disease in Han Chinese in a genome-wide association study

OBJECTIVE

To identify susceptibility loci for Behçet's disease (BD) and elucidate their functional role.

METHODS

A genome-wide association study (GWAS) and functional studies were conducted. A total of 149 patients and 951 controls were enrolled in the initial GWAS, and 554 patients and 1,159 controls were enrolled in the replication study. Real-time polymerase chain reaction, luciferase reporter assay, and enzyme-linked immunosorbent assay were performed.

RESULTS

Our GWAS and replication studies identified a susceptibility locus around STAT4 (single-nucleotide polymorphisms [SNPs] rs7574070, rs7572482, and rs897200; P = 3.36 × 10(-7) to 6.20 × 10(-9) ). Increased expression of STAT4 was observed in individuals carrying the rs897200 risk genotype AA. Consistent with the idea that STAT4 regulates the production of interleukin-17 (IL-17) and interferon-γ, IL17 messenger RNA and protein levels were increased in individuals carrying the rs897200 risk genotype AA. Interestingly, the risk allele A of rs897200 creates a putative transcription factor binding site. To test whether it directly affects STAT4 transcription, an in vitro luciferase reporter gene assay was performed. Higher transcription activity was observed in individuals carrying the risk allele A, suggesting that rs897200 is likely to directly affect STAT4 expression. Additionally, 2 SNPs, rs7574070 and rs7572482, which are tightly linked with rs897200, were cis-expression quantitative trait loci (eQTL) SNPs, suggesting that SNP rs897200 is an eQTL SNP. Most importantly, the clinical disease severity score was higher in individuals with the rs897200 risk genotype AA.

CONCLUSION

These findings strongly suggest that STAT4 is a novel locus underlying BD. We propose a model in which up-regulation of STAT4 expression and subsequent STAT4-driven production of inflammatory cytokines, such as IL-17, constitute a potential pathway leading to BD.

Association between Rho-kinase (ROCK2) gene polymorphisms and Behçet's disease

Behçet's disease (BD) is a multi-systemic vasculitis. The aim of this study was to investigate the association between Rho-kinase (ROCK2) gene polymorphisms and patients with BD in a Turkish population. A total of 194 BD patients and 276 healthy controls with similar age and sex were included to this study. Polymorphisms were analyzed in genomic DNA using a BioMark 96.96 dynamic array system. mRNA from blood samples was extracted, and real-time polymerase chain reaction was performed for ROCK2 gene expression. There were marked changes in both genotype (TT, 41.8%; TA, 30.3%) and allele (T, 57%; A, 43%) frequencies for the rs35768389 (Asp601Val) polymorphism in patients compared with controls (TT, 64.6%; TA, 9.4%, P < 0.0001; T, 69.3%; A, 30.7%, P = 0.0004). Although CC genotype (52.0%) of rs1515219 polymorphism were more frequent, CT genotype (27.7%) were less frequent among the patients than controls (CC, 31.7%, CT, 44.6%, P = 0.0001). There was an increase in C allele (65.8% vs 54.0%) and decrease in T allele frequencies (34.2% vs 46.0%, P = 0.001) in patients. However, no associations were found with rs726843, rs2290156, rs965665, rs10178332, rs2230774, rs6755196, rs10929732, and rs34945852 polymorphisms. There was an increase in peripheral blood mRNA ROCK2 expressions in patients. This is the first study to examine the involvement of ROCK2 gene variation in the risk of incident BD. The results strongly suggest that ROCK2 gene polymorphisms may modify individual susceptibility to BD in the Turkish population.

Genetic variant on PDGFRL associated with Behçet disease in Chinese Han populations

Behçet disease is a complex multisystem disorder. This study aimed to explore the predisposition of PDGFRL at the 8p21.3 locus with Behçet disease and its expression level for different genotypes. A two-stage association study was performed in 719 patients and 1,820 controls for 26 tagSNPs in the PDGFRL gene. Real-time PCR and Bonferroni correction were performed. The first-stage study showed that SNP rs17633132 was associated with Behçet disease (Pc = 5.20 × 10(-3)). Replication and combined studies showed consistent association for rs17633132 T allele and TT genotype (replication: Pc = 3.90 × 10(-4) and 5.70 × 10(-3); combined: Pc = 2.05 × 10(-6) and 3.20 × 10(-4)). No haplotype in PDGFRL was associated with Behçet disease. The expression of PDGFRL in skin from rs17633132 CC genotype individuals was increased compared to that in those with the CT or TT genotype (P = 0.028, P = 0.032, respectively). This study identified a Behçet-disease-associated gene, PDGFRL, and suggests its involvement of Behçet disease by modulating its transcription.

Two-stage association study in Chinese Han identifies two independent associations in CCR1/CCR3 locus as candidate for Behçet's disease susceptibility

Previous GWAS studies from Turkey suggested a potential risk locus at CCR1/CCR3 for Behçet's disease. However, this locus did not reach the GWAS significance threshold and has not yet been examined in other ethnic populations. The current study aimed to explore whether this locus was associated with Behçet's disease in Chinese Han and the functional role of the identified variants. A two-stage association study was performed in 653 patients and 1,685 controls using the iPLEX system. Real-time PCR was performed to examine the expression level of CCR1 and CCR3 genes. Haplotype analysis was used to construct the haplotype block. Logistic regression analysis was applied to calculate the independence of multiple associations. Bonferroni correction was applied to account for multiple testing. First stage analysis showed that ten SNPs, located in 3'UTR, 5'UTR in CCR1 or 5'UTR in CCR3, were significantly associated with Behçet's disease (P(c) = 0.018 to 1.3 × 10(-3)). The associations of six SNPs within this locus are independent after control for the genetic effect of rs17282391 using logistic regression analysis. Haplotype analysis identified three associated haplotypes: H3 (GTGAC), H6 (CCATTA) and H9 (CGA) (P(c) = 0.04 to 7.79 × 10(-4)). Three SNPs rs13084057, rs13092160 and rs13075270 showed consistent association in replication and combining studies (replication P(c) = 5.31 × 10(-5) to 1.44 × 10(-5); combining P(c) = 2.76 × 10(-7) to 6.50 × 10(-8)). Interestingly, eQTLs database reveals that SNP rs13092160 is eQTLs SNP, suggesting that this SNP is likely to be functional SNP that directly affects gene expression. The expression of CCR1 and CCR3 was increased in individuals with the CT genotype of rs13092160 (P < 0.05). No significant difference was found for the mRNA level of CCR1 and CCR3 between Behçet's patients and controls. These findings strongly indicate CCR1/CCR3 as a novel locus underlying Behçet's disease.

Behçet's disease and genes within the major histocompatibility complex region

The role of genetic background in the development of Behçet's disease (BD) is best reflected by the strong association between HLA-B*51 and BD that has been demonstrated across various ethnic groups. The contributions made by other HLA or non-HLA genes to disease susceptibility have been suggested by the results of a number of gene association studies, although the true associations between the genes located within the major histocompatibility complex (MHC) region and BD have often been doubted due to the possibility of linkage disequilibrium of those genes with HLA-B*51. The presence of a true susceptibility gene in the vicinity of HLA-B*51 has also been extensively investigated because of the limited evidence that directly relates HLA-B*51 to the pathogenesis of BD. However, recent genome-wide association studies have confirmed that HLA-B*51 is primarily associated with BD and that there are multiple susceptibility loci other than HLA-B*51. In this review, we discuss BD-associated genes within the MHC region and their biological roles in the pathogenesis of BD.

Genetics of Behçet's Disease

Behçet's disease (BD) is a systemic inflammatory disorder characterized mainly by recurrent oral and genital ulcers and eye involvement. Although the pathogenesis remains poorly understood, a variety of studies have demonstrated that genetic predisposition is a major factor in disease susceptibility. Peculiar geographical distribution of BD along the ancient Silk Road has been regarded as evidence supporting genetic influence. The observed aggregation of BD in families of patients with BD is also supportive for a genetic component in its etiology. HLA-B51 (B510101 subtype) is the most strongly associated genetic marker for BD in countries on the Silk Road. In recent years, several genome-wide association studies and genetic polymorphism studies have also found new genetic associations with BD, which may have a supplementary role in disease susceptibility and/or severity. The author reviewed the HLA and non-HLA genetic association studies.

Genetic susceptibility to Behcet's disease: role of genes belonging to the MHC region

OBJECTIVE

To review the progress in the field of MHC-related genetic susceptibility to Behçet's disease (BD).

METHOD

Systematic review of the English literature between 1 January 1980 and 31 January 2010 using Medline. Case-control, population-based, observational cohort studies investigating the association between BD and HLA-B*51 subtypes, classical and non-classical HLA alleles and other HLA-related genes were selected. The geographical distribution of BD and these susceptibility genes was also taken into consideration. Case and familial case reports were excluded except for case series with more than two patients.

RESULTS

Ninety articles plus 17 obtained from other sources were included in the systematic review. We have found high evidence that a core component of genetic susceptibility to BD is within the MHC region being primarily related to an HLA-B*51 subtype: HLA-B*5101/B*510101. Moreover, HLA-A*26, HLA-B*15, HLA-B*5701 and TNF-α -1031C were independently associated with BD. Data suggest that other HLA (HLA-C, HLA-DR) and HLA-related [MHC Class I chain-related gene A (MIC-A), TNF-α] genes may play a role in BD co-susceptibility or pathogenesis. Finally, the distinctive geographical distribution of BD suggested an evolutionary selection of HLA-B*51 subtypes as the major susceptibility factors for BD.

CONCLUSION

Further studies must be addressed to clarify the functional relevance of the different genes found to be associated with disease susceptibility and the potential interactions between genes located within and outside the MHC region.

HLA-B51/B5 and the risk of Behçet's disease: a systematic review and meta-analysis of case-control genetic association studies

OBJECTIVE

To quantify by meta-analysis the genetic effect of the HLA-B5 or HLA-B51 (HLA-B51/B5) allele on the risk of developing Behçet's disease (BD) and to look for potential effect modifiers.

METHODS

Relevant studies were identified using the PubMed Medline database and manual searches of the literature. Pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were calculated by using the random-effects model. Subgroup meta-analyses and meta-regression analyses were undertaken to investigate the effects of selected study-level parameters on the pooled OR. Heterogeneity was assessed using the I2 statistic. Pooled results were used to calculate population-attributable risks (PAR) for BD in relationship to HLA-B51/B5.

RESULTS

A total of 4,800 patients with BD and 16,289 controls from 78 independent studies (published 1975-2007) were selected. The pooled OR of HLA-B51/B5 allele carriers to develop BD compared with noncarriers was 5.78 (95% CI 5.00-6.67), with moderate between-study heterogeneity (I2 = 61%). The subgroup analyses stratifying studies by geographic locations (Eastern Asia, Middle East/North Africa, Southern Europe, Northern/Eastern Europe) yielded consistent OR ranges (5.31-7.20), with I2 ranges of 52-70%. Univariate random-effects meta-regression indicated the percentage of male BD cases (P = 0.008) as a source of heterogeneity. The PAR within the various geographic areas were estimated at 32-52%.

CONCLUSION

The strength of the association between BD and HLA-B51/B5, and its consistency across populations of various ethnicities, lends further support to this allele being a primary and causal risk determinant for BD. Variations according to sex support an interaction of this allele with BD characteristics.

Population-based prevalence study of Behçet's disease: differences by ethnic origin and low variation by age at immigration

OBJECTIVE

To estimate the prevalence of Behçet's disease (BD) in a multiethnic population living in France, with particular focus on disease risk among immigrants.

METHODS

The study was conducted in a county in the Paris metropolitan area that is home to 1,094,412 adults (ages > or =15 years), of whom 26% are of non-European ancestry. Patients with BD living in this area during 2003 were identified using 3 sources (hospitals, community physicians, and the National Health Insurance database), and diagnoses were verified using the International Study Group criteria. Standardized, year-2003 prevalence rates were computed for the overall population and for each ethnic group. Stratified prevalence rates according to age at immigration to France were calculated to investigate the relationship between age at immigration and BD risk.

RESULTS

Seventy-nine subjects fulfilled our search criteria. The overall prevalence per 100,000 adults was 7.1 (95% confidence interval [95% CI] 3.5-14.4), and the prevalence for populations of European, North African, and Asian ancestry was 2.4 (95% CI 0.6-7.2), 34.6 (95% CI 24.4-47.5), and 17.5 (95% CI 10.7-27.2), respectively. Within the migrant population of either North African or Asian ancestry, BD prevalences were similar for residents born in France, residents <15 years old at immigration, and residents > or =15 years old at immigration.

CONCLUSION

Our findings indicate that the prevalence of BD among immigrants of North African or Asian ancestry is significantly higher than that in the European-origin population, and comparable with rates reported from North Africa and Asia. Moreover, our results suggest that BD risk is not related to age at immigration. These findings support the hypothesis that BD has a primarily hereditary basis.

Behçet's disease: recent advances in early diagnosis and effective treatment

Behçet's disease (BD) is a chronic, multisystem, inflammatory disorder that is classified among the systemic vasculitidies. Its cause has yet to be determined, but genetic and environmental factors and immune dysregulation are thought to play a role in its pathogenesis. The diagnosis of the disease and recognition and separation from disorders that may mimic BD may be difficult, especially in areas where the disease is uncommon. Certainty as to the best treatments for the various manifestations of BD is often unclear due to limited randomized controlled trials. However, existing consensus statements and expert opinions should help to guide therapy. This review examines important recent contributions to help the clinician more readily recognize patients with the disease and institute appropriate care.

The unique features of vasculitis in Behçet's syndrome

The presence of a true vasculitis is difficult to discern in some of the more common manifestations of Behçet's syndrome, like the papulopustular lesions of the skin. On the other hand, a true vasculitis is seen in all vessel sizes in the majority of the patients. The pathogenesis is not yet known. A Th1-type inflammatory reaction is seen like in some other primary vasculitides. However, in contrast to other vasculitides, granuloma formation is absent. Behçet's syndrome is unique among the vasculitides with its differing geographic distribution in disease expression, the distinctly more severe disease among the male, the predominance of venous disease, and the generally abating disease course with lack of associated increased atherosclerosis.

Genetics of ankylosing spondylitis: An update

Substantive evidence exists that genetic factors play a pivotal role in susceptibility to ankylosing spondylitis (AS). HLA-B27 remains the most convincing and universal association of a genetic factor with AS. Over the last decade there has been immense interest in elucidating genetic variants outside the major histocompatibility complex region. Due to larger AS datasets along with recent advancements in the characterization of genetic markers and large-scale genotyping platforms, replicated non-major histocompatibility candidates have now emerged. This article reviews the current evidence regarding the genetics of AS, with an emphasis on the recent major advances, and it discusses the challenges and limitations in interpreting these studies.

PTPN22 gene polymorphism in Behçet's disease

A functional single nucleotide polymorphism (SNP) of PTPN22 gene encoding the protein tyrosine phosphatase has been reported to be associated with autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus and type I diabetes. PTPN22 R620W polymorphism has a wide variation of allelic frequencies among different populations. This polymorphism is investigated in Turkish patients with Behçet's disease (BD), a systemic vasculitis with immune activation. DNA samples from 134 patients with BD and 177 healthy controls are genotyped by polymerase chain reaction (PCR)-restriction fragment length polymorphism method for the SNP (rs2476601, A/G) of PTPN22 gene. Polymorphic region was amplified by PCR and digested with XcmI enzyme. The frequency of heterozygous genotype (AG) was 5.1% (9/177) in control group, whereas polymorphic allele was not present in the whole BD group (P = 0.012, OR 0.65, 95% confidence interval 0.0-1.1). Both the lower prevalence in the general population and the absence in BD show the limited role of PTPN22 polymorphism in the pathogenesis of autoimmunity in Turkey.

Low-dose intra-venous cyclophosphamide therapy in a patient with neurological complications of Behçet’s disease

Behçet's disease (BD) is a chronic relapsing-remitting inflammatory disorder of unknown origin, affecting multiple organs. Neurological involvement is one of the most devastating manifestations of BD and may be fatal. We report a 36-year-old woman with neuro-Behçet who was treated with low-dose pulse cyclophosphamide (St. Thomas' protocol) and methylprednisolone, with almost complete clinical remission.

Interleukin-18 Promoter Polymorphisms in Patients With Behçet’s Disease

Behçet's disease (BD) is an idiopathic systemic inflammatory disease and is considered to be a T helper 1 (Th1) type cytokine driven disorder. Moreover, levels of interleukin-18 (IL-18), a pivotal mediator of Th1 cytokine response, have been reported to be upregulated in BD. Therefore, we investigated the distribution of IL-18 promoter -607 C/A and -137 G/C polymorphisms in 103 BD patients (mean age 41.0 years; 48 male, 55 female) using allele-specific-polymerase chain reaction. As compared with healthy control subjects, BD patients had a significantly higher frequency of the -607 CC genotype (42.7% vs 23.3%, odds ratio [OR] = 2.455, 95% confidence interval [CI] = 1.350-4.461, p(c) = 0.021) and a higher frequency of the -607 C allele (60.7% vs 48.1%, OR = 1.668, 95% CI = 1.129-2.464, p = 0.0101). Haplotype analysis showed that BD patients had significantly less -607A/-137G haplotype (27.3% vs 44.2%, OR = 0.469, 95% CI = 0.268-0.820, p(c) = 0.032) and -607A/-137G haplotype homozygote (5.8% vs 20.4%, OR = 0.242, 95% CI = 0.096-0.612, p(c) = 0.014) than control subjects. In addition, the frequency of -607C/-137G haplotype homozygote was significantly higher in BD patients than control subjects (48.5% vs 20.4%, OR = 3.684, 95% CI = 1.997-6.791, p(c) = 0.0014). Although there were no associations between the polymorphisms and clinical manifestations or severity, patients with the -607 CC genotype or -607C/-137G haplotype homozygote showed significantly earlier symptom development (p = 0.034 by ANOVA; p = 0.009 by t-test, respectively) than those with other genotypes or diplotypes. These results suggest that the IL-18 promoter gene is a candidate susceptibility gene in BD patients.

Juvenile spondyloarthropathies associated with Mycoplasma pneumoniae infection

BACKGROUND

Reactive arthritis (ReA) has been sporadically reported as triggered by Mycoplasma pneumoniae. This study examined the potential relationship between the acute M. pneumoniae infection and juvenile spondyloarthropathy (jSpA) in children.

PATIENTS AND METHODS

Twelve patients with ReA secondary to acute M. pneumoniae were examined. M. pneumoniae-specific IgM, IgG and IgA antibodies were serologically confirmed by enzyme-linked immunosorbent assay (ELISA) tests (Savyon Diagnost., Israel). Due to the early appearance and relatively short life time of M. pneumoniae-specific IgM antibodies, their detection allowed the diagnosis of acute infection using single serum sample, confirmed by parallel serum in 7 of 12 patients. Specific IgM and IgG titers higher than 10 U/l were considered positive and those higher than 50 U/l as highly positive. Specific IgA antibodies were detected in only one patient.

RESULTS

Four patients were female and eight were male. The mean age at onset was 9 years, and the mean duration of follow-up was 24.1 months (range 18-32). The mean number of involved joints was 2.8, and the knee joints were involved in 7 of 12 patients. The mean recovery time was 4.5 weeks (range 1-28) in eight reactive arthritis (ReA) cases; three patients developed enthesitis-related arthritis, and in one patient, genuine juvenile ankylosing spondylitis (jAS) was diagnosed. Two patients were HLA-B27-positive, and one patient was HLA-B7/B27-positive. Six patients had preceding respiratory symptoms, and five were treated with antibiotics.

CONCLUSIONS

Our findings provide clear evidence of ReA diagnosis following an acute M. pneumoniae infection that in four patients progressed to chronic jSpA. Our results suggest that detecting M. pneumoniae-specific antibodies in serological screening of jSpA patients might be useful. It is presently unclear whether antibiotic treatment would change the disease course in those patients.

Association of vascular endothelial growth factor gene polymorphisms with behcet disease in a Korean population

Vascular endothelial growth factor (VEGF) is important for angiogenesis and inflammation, both of which are codependent and contribute to the pathophysiology of Behcet disease (BD). The increased expressions of VEGF have been observed in the active stage and in the ocular inflammation of BD. Polymorphisms of the VEGF gene have been associated with chronic inflammatory disease including rheumatoid arthritis. We sought to investigate whether polymorphisms on the regulatory region of the VEGF gene are associated with susceptibility of Korean patients with BD. One hundred one native Korean patients with BD and 138 healthy unrelated controls were recruited. Genotype and allele frequencies of the four selected polymorphisms (-2578, -1154, -634, and 936) were not different between the BD group and controls. Among the BD patients, the frequency of the -634 CC genotype decreased in patients with uveitis (2.6% vs. 20.6%, adjusted OR = 0.100, 95% CI 0.011-0.875, p = 0.037), although it became insignificant after correction for multiple comparisons. These results indicate that the VEGF gene polymorphisms are not associated with BD in the Korean population, but they may be involved in the development of the ocular inflammation of BD.