Co-Localization of Susceptibility Loci for Psoriasis (PSORS4) and Atopic Dermatitis (ATOD2) on Human Chromosome 1q21

Evolutionary context of psoriatic immune skin response

The skin is vital for protecting the body and perceiving external stimuli in the environment. Ability to adapt between environments is in part based on skin phenotypic plasticity, indicating evolved homeostasis between skin and environment. This homeostasis reflects the greater relationship between the body and the environment, and disruptions in this balance may lead to accumulation of susceptibility factors for autoimmune conditions like psoriasis. In this study, we examined the relationship between rapid, lineage-specific evolution of human skin and formation of psoriatic skin responses at the transcriptome level. We collected skin tissue biopsies from individuals with psoriasis and compared gene expression in psoriatic plaques to non-plaque psoriatic skin. We then compared these data with non-psoriatic skin transcriptome data from multiple primate species. We found 67 genes showing human-specific skin expression that are also differentially regulated in psoriatic skin; these genes are significantly enriched for skin barrier function, immunity and neuronal development. We identified six gene clusters with differential expression in the context of human evolution and psoriasis, suggesting underlying regulatory mechanisms in these loci. Human and psoriasis-specific enrichment of neuroimmune genes shows the importance of the ongoing evolved homeostatic relationship between skin and external environment. These results have implications for both evolutionary medicine and public health, using transcriptomic data to acknowledge the importance of an individual’s surroundings on their overall health.

The skin is important for protecting the body from the environment and perceiving external stimuli, creating an evolved balance between skin and the environment. We compare skin gene expression in humans with psoriasis to humans and non-human primates without psoriasis to better understand human-specific evolutionary changes in the skin. Our results suggest important evolutionary links between skin perception, human-specific skin development and immune response.

Pharmacogenomics: An Update on Biologics and Small-Molecule Drugs in the Treatment of Psoriasis

Pharmacogenomic studies allowed the reasons behind the different responses to treatments to be understood. Its clinical utility, in fact, is demonstrated by the reduction in adverse drug reaction incidence and the improvement of drug efficacy. Pharmacogenomics is an important tool that is able to improve the drug therapy of different disorders. In particular, this review will highlight the current pharmacogenomics knowledge about biologics and small-molecule treatments for psoriasis. To date, studies performed on genes involved in the metabolism of biological drugs (tumor necrosis factor inhibitors and cytokines inhibitors) and small molecules (apremilast, dimethyl fumarate, and tofacitinib) have provided conflicting results, and further investigations are necessary in order to establish a set of biomarkers to be introduced into clinical practice.

Eczema as an adverse effect of anti-TNFα therapy in psoriasis and other Th1-mediated diseases: a review

INTRODUCTION

There have been rare reports of eczema occurring as an adverse effect of anti-tumor necrosis factor-alpha (TNFα) therapy.

METHODS

A literature search was conducted on PubMed for articles describing new onset or worsening of preexisting eczema during anti-TNFα therapy for the treatment of various inflammatory diseases.

RESULTS

Eczema as an adverse effect of anti-TNFα therapy may occur in approximately 5-20% of patients with various Th1-mediated inflammatory diseases such as psoriasis, inflammatory arthritis and inflammatory bowel disease. Personal history of atopy appears to increase this risk. Out of the anti-TNFα agents indicated for the treatment of moderate-to-severe psoriasis, infliximab may be more strongly associated with development or exacerbation of preexisting eczema.

DISCUSSION

Inhibitors of key mediators in the Th1 pathway such as TNFα are successful therapeutic targets for the treatment of various inflammatory conditions such as psoriasis, psoriatic arthritis, rheumatoid arthritis and inflammatory bowel disease. Blocking the Th1 pathway may create an imbalance favoring increased activity of the opposing Th2 pathway implicated in inflammatory conditions such as eczema. Further research is needed to better understand the role of the Th1/Th2 balance in various inflammatory diseases and how the immunologic environment is affected by immunotherapies.

Regulation of the dynamic chromatin architecture of the epidermal differentiation complex is mediated by a c-Jun/AP-1-modulated enhancer

The epidermal differentiation complex (EDC) locus comprises a syntenic and linear cluster of genes whose concomitant expression is a hallmark feature of differentiation in the developing skin epidermis. Many of the EDC proteins are cross-linked together to form the cornified envelope, an essential and discrete unit of the mammalian skin barrier. The mechanism underlying coordinate transcriptional activation of the EDC is unknown. Within the human EDC, we identified an epidermal-specific regulatory enhancer, 923, which responded to the developmental and spatiotemporal cues at the onset of epidermal differentiation in the mouse embryo. Comparative chromosomal conformation capture assays in proliferating and differentiated primary mouse keratinocytes revealed multiple physiologically sensitive chromatin interactions between the 923 enhancer and EDC gene promoters, thus depicting the dynamic chromatin topology of the EDC. We elucidate a mechanistic link between c-Jun/AP-1 and 923, whereby AP-1- and 923-mediated EDC chromatin remodeling are required for functional EDC gene activation. Thus, we identify a critical enhancer/transcription factor axis governing the dynamic regulation of the EDC chromatin architecture and gene expression and provide a framework for future studies toward understanding gene regulation in cutaneous diseases.

Grainyhead-like 2 (GRHL2) inhibits keratinocyte differentiation through epigenetic mechanism

We recently identified Grainyhead-like 2 (GRHL2), a mammalian homolog of Grainyhead in Drosophila, to be a novel transcription factor that regulates hTERT gene expression and enhances proliferation of normal human epidermal keratinocytes (NHEK). In the current study, we show that GRHL2 impairs keratinocyte differentiation through transcriptional inhibition of the genes clustered at the epidermal differentiation complex (EDC), located at chromosome 1q21. Gene expression profiling and subsequent in vitro assays revealed consistent downregulation of EDC genes, for example, IVL, KRT1, FLG, LCEs, and SPRRs, in NHEK expressing exogenous GRHL2. In vivo binding assay by chromatin immunoprecipitation revealed GRHL2 association at the promoter regions of its target genes, many of which belong to EDC. Exogenous GRHL2 expression also inhibited recruitment of histone demethylase Jmjd3 to the EDC gene promoters and enhanced the level of histone 3 Lys 27 trimethylation enrichment at these promoters. Survey of GRHL2 expression in human skin tissues demonstrated enhanced protein and mRNA levels in chronic skin lesions with impaired keratinocyte differentiation, for example, atopic dermatitis and psoriasis, compared with normal epidermis. These data indicate that GRHL2 impairs epidermal differentiation by inhibiting EDC gene expression through epigenetic mechanisms and support its role in the hyperproliferative skin diseases.

PTPN22 polymorphisms may indicate a role for this gene in atopic dermatitis in West Highland white terriers

Background

Canine atopic dermatitis is an allergic inflammatory skin disease common in West Highland white terriers. A genome-wide association study for atopic dermatitis in a population of West Highland white terriers identified a 1.3 Mb area of association on CFA17 containing canine protein tyrosine phosphatase non-receptor type 22 (lymphoid) PTPN22. This gene is a potential candidate gene for canine atopic dermatitis as it encodes a lymphoid-specific signalling mediator that regulates T-cell and possibly B-cell activity.

Findings

Sequencing of PTPN22 in three atopic and three non-atopic West Highland white terriers identified 18 polymorphisms, including five genetic variants with a bioinformatically predicted functional effect. An intronic polymorphic repeat sequence variant was excluded as the cause of the genome-wide association study peak signal, by large-scale genotyping in 72 West Highland white terriers (gene-dropping simulation method, P = 0.01).

Conclusions

This study identified 18 genetic variants in PTPN22 that might be associated with atopic dermatitis in West Highland white terriers. This preliminary data may direct further study on the role of PTPN22 in this disease. Large scale genotyping and complementary genomic and proteomic assays would be required to assess this possibility.

IL-23-mediated epidermal hyperplasia is dependent on IL-6

Psoriasis is a chronic inflammatory skin disease primarily driven by Th17 cells. IL-23 facilitates the differentiation and induces complete maturation of Th17 cells. Lesional psoriatic skin has increased levels of IL-23 and recent studies show that intradermal injections of IL-23 induce a psoriasis-like skin phenotype in mice. We have now characterized the IL-23-induced skin inflammation in mice at the molecular level and found a significant correlation with the gene expression profile from lesional psoriatic skin. As observed in psoriasis, the pathogenesis of the IL-23-induced skin inflammation in mice is driven by Th17 cells. We demonstrate a dramatic upregulation of IL-6 mRNA and protein after intradermal injections of IL-23 in mice. Using IL-6(-/-) mice we show that IL-6 is essential for development of the IL-23-elicited responses. Despite producing high levels of IL-22, IL-6(-/-) mice were unable to express the high-affinity IL-22 receptor chain and produced minimal IL-17A in response to intradermal injections of IL-23. In conclusion, we provide evidence for the critical role played by IL-6 in IL-23-induced skin inflammation and show that IL-6 is required for expression of IL-22R1A.

Genetic variations associated with psoriasis and psoriatic arthritis found by genome-wide association

Psoriasis and psoriatic arthritis are immune disorders with a complex polygenic basis. HLA-Cw6, which lies in the major histocompatibility region on chromosome 6, is considered the major genetic determinant of psoriasis. Recent genome-wide association studies have identified new variants outside of the MHC with relevance to the immunology of psoriasis. Variants in or near genes that encode subunits of cytokines (IL12B, IL23A) or cytokine receptors (IL23R) are interesting given that the gene product of IL12B, p40, is the target of a recently approved monoclonal antibody therapy for psoriasis (ustekinumab). Association with psoriasis and psoriatic arthritis has been found in TNFAIP3 and TNFIP1, ubiquitin ligases in the NF-kappaB pathway, and IL13, a Th2 cytokine. Copy number variation of human beta-defensin and late cornified envelope genes also associate with psoriasis. Many of these genetic variations also associate with immune disorders considered psoriatic co-morbidities, including Crohn's disease and diabetes.

Broad defects in epidermal cornification in atopic dermatitis identified through genomic analysis

BACKGROUND

Psoriasis and atopic dermatitis (AD) are common, complex inflammatory skin diseases. Both diseases display immune infiltrates in lesions and epidermal growth/differentiation alterations associated with a defective skin barrier. An incomplete understanding of differences between these diseases makes it difficult to compare human disease pathology to animal disease models.

OBJECTIVE

To characterize differences between these diseases in expression of genes related to epidermal growth/differentiation and inflammatory circuits.

METHODS

We performed genomic profiling of mRNA in chronic psoriasis (n = 15) and AD (n = 18) skin lesions compared with normal human skin (n = 15).

RESULTS

As expected, clear disease classifications could be constructed on the basis of expected immune polarity (T(H)1, T(H)2, T(H)17) differences. However, even more striking differences were identified in epidermal differentiation programs that could be used for precise disease classifications. Although both psoriasis and AD skin lesions displayed regenerative epidermal hyperplasia, which is a general alteration in epidermal growth, keratinocyte terminal differentiation was differentially polarized. In AD, we found selective defects in expression of multiple genes encoding the cornified envelope, with the largest alteration in loricrin (expressed at 2% of the level of normal skin). At the ultrastructural level, the cornified envelope in AD was broadly defective with highly decreased compaction of corneocytes and reduced intercellular lipids. Hence, the entire keratinocyte terminal differentiation program (cytoplasmic compaction, cornification, and lipid release) is defective in AD, potentially underlying the immune differences.

CONCLUSION

Our study shows that although alterations in barrier responses exist in both diseases, epidermal differentiation is differentially polarized, with major implications for primary disease pathogenesis.

Replication of LCE3C-LCE3B CNV as a risk factor for psoriasis and analysis of interaction with other genetic risk factors

Recently, a deletion of two late cornified envelope (LCE) genes within the epidermal differentiation complex on chromosome 1 was shown to be overrepresented in 1,426 psoriasis vulgaris (PsV) patients of European ancestry. In this study, we report a confirmation of this finding in 1,354 PsV patients and 937 control individuals of German origin. We found an allele frequency of the deletion of 70.9% in PsV patients and of 64.9% in control individuals (chi(2)=17.44, P=2.97 x 10(-5), odds ratio (95% confidence interval)=1.31 (1.15-1.48)). The overall copy number of the two LCE genes had no influence on the age of onset, but we observed a dosage effect at the genotype level. There was no evidence of statistically significant interaction with copy number of the beta-defensin cluster on 8p23.1 or with an IL-23R pathway variant in a combined data set of German and Dutch individuals, whereas evidence for interaction with the PSORS1 risk allele in German individuals was marginal and did not remain significant after correction for multiple testing. Our study confirms the recently published finding that the deletion of the two LCE genes is a susceptibility factor for PsV with dosage effect, while, because of power limitation, no final conclusion regarding interaction with other PsV risk factors can be made at this stage.

Useful tools for the management of atopic dermatitis

Eczema, frequently named atopic dermatitis, is the most frequent chronic skin disease of early childhood, with a high prevalence in industrialized countries and a relapsing-remitting course that is responsible for a serious burden on affected children and their families. Even though most facets of this disease are nowadays well known and numerous guidelines are available, some confusion still exists regarding certain aspects. First, several names have been proposed for the disorder. We suggest that the name and definition adopted by the World Allergy Organization should be used: 'eczema,' divided into 'atopic,' when an allergic sensitization can be demonstrated, and 'non-atopic,' in the absence of sensitization. Several diagnostic criteria have been proposed, but at present the two most reliable are the 2003 revision by the American Academy of Dermatology of the Hanifin-Rajka criteria, and those by Williams revised in 2005. To date, 20 different clinical scores have been published to assess the severity; however, only the EASI (Eczema Area and Severity Index), the SCORAD (SCORing Atopic Dermatitis), and the POEM (Patient-Oriented Eczema Measure) seem to have been adequately validated and are recommended for use in clinical practice and trials. The diagnostic tests to identify associated allergy or sensitization include skin-prick tests, determination of the specific IgE in serum using different assays, and atopy patch tests; in the case of suspected food allergy, a food challenge may be necessary to define the diagnosis. To evaluate quality of life, tools exist that allow both the child's and family's impairment to be considered. In addition, several algorithms exist to help decide therapy on a step-wise basis. However, such guidelines and algorithms represent only an aid to the physician and not an obligatory directive, since the ultimate judgment regarding any therapy must be performed by the physician and tailored to individual needs. A clear and validated definition of eczema control would permit better monitoring of the disease, similar to the situation with asthma in recent years. Finally, the review examines the role of special textiles in diminishing Staphylococcus aureus skin superinfection, of house dust-mite avoidance measures, and of educational programs for patients and their families, which may all help improve eczema.

FcRL3 gene promoter variant is associated with peripheral arthritis in Crohn's disease

BACKGROUND

The mechanisms responsible for the pathogenesis of peripheral arthropathies (PA) in Crohn's disease (CD) are largely unknown, although many studies indicate that genetic and environmental factors are likely to contribute to risk.

METHODS

Because variants in the Fc receptor-like 3 (FcRL3) gene have recently been associated with rheumatoid arthritis and several other autoimmune diseases, we tested 2 FcRL3 promoter variants (-169 C>T and -110 G>A) for association with PA in Spanish CD patients that were recruited from a single center and followed for at least 4 years (mean follow-up time, 11 years).

RESULTS

Among the 342 CD patients evaluated, there were 88 cases of peripheral arthropathy; 31 were classified as arthritis and 57 were classified as arthralgia. We used contingency tables and logistic regression to test for association between PA or either subtype and FcRL3 and other factors that have previously been associated with extraintestinal manifestations in CD.

CONCLUSIONS

We found that female sex, colonic involvement, and the AA genotype at -110 G>A were associated with increased risk of both subtypes of PA, although the association appears to be stronger for arthritis than for arthralgia.

An association study of 22 candidate genes in psoriasis families reveals shared genetic factors with other autoimmune and skin disorders

Psoriasis is a common inflammatory and hyperproliferative skin disease. Recent studies have reported that common genetic factors may underlie both skin and immune-mediated disorders. We hypothesized that such genes may be involved in susceptibility to psoriasis, and undertook an association analysis of 22 candidate genes in a set of French high-risk psoriasis families. One hundred fifty-three single-nucleotide polymorphisms (SNPs) were genotyped and the transmission of alleles in nuclear families was analyzed using the FBAT (family-based association test). To further investigate suggestive associations, LNM (logistic-normal models) and MQLS (modified quasi-likelihood score) methods, which take the whole pedigree structure information of families into consideration, were also applied. Our study supported the involvement of six candidate genes in susceptibility to psoriasis: SCL12A8, which belongs to the solute carrier gene family; FLG and TGM5, which are involved in epidermal differentiation; CARD15 and CYLD, which modulate the transcription factor NF-kB; and IL1RN, which encodes an IL receptor antagonist. Furthermore, we found evidence for interaction between the major risk allele, HLA-Cw6, and CARD15, CYLD, and TGM5 susceptibility alleles. Taken together, our data show that shared genetic factors may contribute to the etiology of both psoriasis and other skin or immune-mediated disorders.

Characterisation of psoriasis susceptibility locus 6 (PSORS6) in patients with early onset psoriasis and evidence for interaction with PSORS1

BACKGROUND

Psoriasis is a genetically complex, chronic inflammatory skin disease. The authors have previously identified a susceptibility locus on chromosome 19p13 (PSORS6).

METHODS AND RESULTS

In a follow-up linkage disequilibrium (LD) study in an independent family based cohort, the authors found evidence for association to a newly discovered microsatellite at this locus (D19SPS21, p<5.3x10(-5)). An LD based association scan in 300 trios revealed association to several single, single nucleotide polymorphisms (SNPs) in one LD block. When the authors stratified this cohort for carrying the PSORS1 risk allele at the HLA-C locus, evidence for association became much stronger at single SNP and haplotype levels (p values between 1.0x10(-4) and 8.0x10(-4)). In a replication study of 1114 patients and 937 control individuals, evidence for association was also observed after stratification to the PSORS1 risk allele. In both study groups, logistic regression showed evidence for interaction between the risk alleles at PSORS1 and PSORS6. Best p values for rs12459358 in both study groups remained significant after correction for multiple testing. The associated LD block did not comprise any known genes. Interestingly, an adjacent gene, MUC16, coding for a large glycosylated protein expressed in epithelia and of unknown function, could be shown to be also expressed in tissues relevant for pathogenesis of psoriasis such as skin and thymus. Immunohistochemical analyses of skin revealed focal staining for MUC16 in suprabasal epidermal cells. Further functional studies are required to clarify its potential role in psoriasis and identify the causal variant(s) at this locus.

CONCLUSION

The data establish PSORS6 as a confirmed psoriasis susceptibility locus showing interaction with PSORS1.

Deletion of LCE3C and LCE3B genes at PSORS4 does not contribute to susceptibility to psoriatic arthritis in German patients

Introduction

Psoriasis susceptibility locus 4 (PSORS4) is a susceptibility locus for psoriasis vulgaris (PsV), a common inflammatory, hyperproliferative skin disorder. Recently, a deletion of 2 late cornified envelope (LCE) genes within epidermal differentiation complex on chromosome 1 was shown to be enriched in 1426 patients with PsV, suggesting compromised barrier function in deletion carriers. This genetic association was subsequently confirmed in a German cohort.

Methods

In order to investigate whether this variant also predisposes to psoriatic arthritis (PsA), this deletion and 3 single nucleotide polymorphisms (SNPs) in strong linkage disequilibrium with it were genotyped in a case-control cohort of 650 patients and 937 control individuals of German origin.

Results

LCE deletion frequency did not significantly differ between patients with PsA and controls (65.0% vs 65.5%). Similarly, no evidence for association to the three SNPs was observed.

Discussion

This is the first non-human leucocyte antigen (HLA) risk factor predisposing only to skin type of psoriasis, supporting the concept of partially overlapping but different aetiological factors underlying skin and joint manifestations.

Psoriasis: the epidermal component

Besides the infiltrate of immune cells in psoriatic lesions, the principal characteristic changes in the skin are changes of the epidermal architecture and alterations of keratinocyte differentiation, which are distinct from other inflammatory skin diseases clinically and histologically. Several lines of evidence suggest that 3 of the 9 psoriasis susceptibility loci identified today might play a role in the keratinocyte differentiation program. Therefore, besides the dysregulation of the immune system, intrinsic epidermal components are also likely to play a role in triggering and/or sustaining the disease process and contribute to the chronicity of psoriasis and its frequent relapses.

Association between P478S polymorphism of the filaggrin gene and risk of psoriasis in a Chinese population in Taiwan

Abnormal keratinocyte terminal differentiation is one of the important characteristics of psoriatic lesions. Filaggrin (FLG) is a key protein that facilitates the terminal differentiation of the epidermis. Thus, FLG genetic variants may modify the risk of psoriasis. In total, 314 patients with psoriasis and 611 control subjects were analyzed for the presence of FLG R501X, 2282del4 mutations, and P478S (rs11584340, C/T base change) polymorphism by polymerase chain reaction (PCR). The analysis revealed that both the R501X and 2282del4 mutations were not present in a subset of 200 patients (64%) with psoriasis. In contrast, a marginally significant difference (P = 0.020) was found in the distribution of rs11584340 genotype frequencies between psoriatic patients and controls. The frequency of the TT genotype in psoriasis patients was significantly higher than in controls (37.9% vs. 29.1%, respectively, P = 0.007). The T allele frequency of patients (60.5%) was also significantly higher than that of controls (53.9%) (P = 0.007). After adjusting for age and gender, carriers of the TT genotype were 1.46 (95% CI, 1.08-1.96) times more likely than non-carriers to have psoriasis (P = 0.013). In conclusion, our results suggest that FLG P478S polymorphism may confer susceptibility to the development of psoriasis among Taiwanese Chinese.

ADAM33, a new candidate for psoriasis susceptibility

Psoriasis is a chronic skin disorder with multifactorial etiology. In a recent study, we reported results of a genome-wide scan on 46 French extended families presenting with plaque psoriasis. In addition to unambiguous linkage to the major susceptibility locus PSORS1 on Chromosome 6p21, we provided evidence for a susceptibility locus on Chromosome 20p13. To follow up this novel psoriasis susceptibility locus we used a family-based association test (FBAT) for an association scan over the 17 Mb candidate region. A total of 85 uncorrelated SNP markers located in 65 genes of the region were initially investigated in the same set of large families used for the genome wide search, which consisted of 295 nuclear families. When positive association was obtained for a SNP, candidate genes nearby were explored more in detail using a denser set of SNPs. Thus, the gene ADAM33 was found to be significantly associated with psoriasis in this family set (The best association was on a 3-SNP haplotype P = 0.00004, based on 1,000,000 permutations). This association was independent of PSORS1. ADAM33 has been previously associated with asthma, which demonstrates that immune system diseases may be controlled by common susceptibility genes with general effects on dermal inflammation and immunity. The identification of ADAM33 as a psoriasis susceptibility gene identified by positional cloning in an outbred population should provide insights into the pathogenesis and natural history of this common disease.

On the role of the epidermal differentiation complex in ichthyosis vulgaris, atopic dermatitis and psoriasis

Undisturbed epidermal differentiation is crucial for an intact skin barrier function. The epidermal differentiation complex (EDC) is a cluster of genes on chromosome 1q21 encoding proteins that fulfil important functions in terminal differentiation in the human epidermis, including filaggrin, loricrin, S100 proteins and others. Recently, evidence emerged that variation within EDC genes plays an important role in the pathogenesis of three common skin disorders, ichthyosis vulgaris, atopic dermatitis (AD) and psoriasis. Two loss-of-function mutations in the filaggrin (FLG) gene, R501X and 2282del4, were identified as causative for ichthyosis vulgaris in 15 affected European families, and the mode of inheritance was found to be semidominant. As ichthyosis vulgaris and AD often occur concomitantly in affected individuals, these two mutations were subsequently investigated in AD patients and found to be strongly associated with the disease. Following this first report, seven replication studies have been performed that all confirm an association of these two mutations with AD (or AD subtypes) in several European cohorts. Additionally, two unique loss-of-function mutations in the FLG gene were identified in Japanese ichthyosis vulgaris families and found to be associated with AD in a Japanese cohort. Thus, the FLG mutations are among the most consistently replicated associations for AD. Additionally, linkage analysis has suggested that variation within the EDC might also predispose for psoriasis but the exact susceptibility variation(s) have not yet been elucidated. Taken together, these findings convincingly demonstrate the important role of barrier dysfunction in various common skin disorders.

Filaggrin's Fuller Figure: A Glimpse into the Genetic Architecture of Atopic Dermatitis

Prevalent mutations in the FLG gene underlie the common skin disorder ichthyosis vulgaris and are significant risk factors for atopic dermatitis (eczema). The recent publication of a strategy to sequence this difficult gene identifies a spectrum of both prevalent and rare mutations that collectively have a significant impact on susceptibility to atopic disease.

Is FCRL3 a new general autoimmunity gene?

Autoimmunity is a multistep pathogenic process, which arises in genetically predisposing individuals as a result of the harmful influence of environmental factors causing the breakdown of immune tolerance and induction of self-reactive immune response. Recent findings resolved common pathogenic mechanisms shared between different autoimmune diseases and suggested for the existence of genetic loci that could be involved in general autoimmunity and hence contribute to susceptibility of several autoimmune diseases. To date, several loci responsible for general autoimmunity have been identified. The Fc receptor-like 3 (FCRL3) gene is one of those loci for which a significant association with a number of autoimmune diseases such as rheumatoid arthritis (RA), autoimmune thyroid disease, and systemic lupus erythematosus (SLE) has been recently shown in Japanese. However, studies in Caucasians failed to confirm a strong association of this gene with RA and SLE and therefore made questionable the putative role of FCRL3 in general autoimmunity. In this review, we discuss whether the FCRL3 gene is a newly discovered gene contributing to shared susceptibility between autoimmune diseases.