Single-cell sequencing reveals distinct immune cell features in cutaneous lesions of pemphigus vulgaris and bullous pemphigoid.

Bullous pemphigoid (BP) and pemphigus vulgaris (PV) are two common subtypes of autoimmune bullous disease (AIBD). The key role of circulating autoreactive immune cells contributing to skin damage of AIBD has been widely recognized. Nevertheless, the immune characteristics in cutaneous lesions remain unclear. Here, we performed single-cell RNA sequencing (scRNA-seq) and single-cell VDJ sequencing (scRNA-seq) to generate transcriptional profiles for cells and T/B cell clonetype in skin lesions of BP and PV. We found that the proportions of NK&T, macrophages/ dendritic cells, B cells, and mast cells increased in BP and PV lesions. Then, BP and PV cells constituted over 75% of all myeloid cell subtypes, CD4+ T cell subtypes and CD8+ T cell subtypes. Strikingly, CD8+ Trm was identified to be expanded in PV, and located in the intermediate state of the pseudotime trajectory from CD8+ Tm to CD8+ Tem. Interestingly, CD8+ Tem and CD4+ Treg highly expressed exhaustion-related genes, especially in BP lesions. Moreover, the enhanced cell communication between stromal cells and immune cells like B cells and macrophages/ dendritic cells was also identified in BP and PV lesions. Finally, clone expansion was observed in T cells of BP and PV compared with HC, while CD8+ Trm represented the highest ratio of hyperexpanded TCR clones among all T cell subtypes. Our study generally depicts a large and comprehensive single-cell landscape of cutaneous lesions and highlights immune cell features in BP and PV. This offers potential research targets for further investigation.

Whole-Exome Sequencing Reveals the Genomic Profile and IL6ST Variants as a Prognostic Biomarker of Paraneoplastic Pemphigus-Associated Unicentric Castleman Disease.

Unicentric Castleman disease (UCD) is a rare lymphoproliferative disorder. Paraneoplastic pemphigus (PNP) is a major complication associated with poor UCD prognosis. However, the genomic profiles and prognostic biomarkers of PNP-associated UCD remain unclear. In this study, we performed whole-exome sequencing analysis for 28 matched tumor-normal pairs and 9 tumor-only samples to define the genomic landscape of Chinese patients with PNP-associated UCD. An integrative analysis was performed to identify somatic variants, the mutational signatures, and key pathways in tumors. Besides, we analyzed the relationship among mutated genes, clinical characteristics, and prognosis. Sixty-one somatic mutant genes were identified in >1 patient with PNP-associated UCD. Specifically, IL6ST and PDGFRB were the most frequently mutated genes (32%), followed by DPP6 (18%) and MUC4 (18%). Signaling molecules and interactions, cellular processes, and signal transduction pathways were enriched. Furthermore, we found that poor overall survival was related to IL6ST variants (P = .02). Finally, we classified PNP-associated UCD into 4 genomic subgroups: IL6ST, PDGFRB, IL6ST-PDGFRB, and an unknown subgroup. In summary, we defined the molecular profile of PNP-associated UCD and identified a potential molecular biomarker for predicting prognosis, which may provide therapeutic targets for treating this severe disorder.

miRNA implication in the pathogenesis and the outcome of Tunisian endemic pemphigus foliaceus.

Pemphigus foliaceus (PF) is a bullous autoimmune skin disease diagnosed through sera and skin analyses. PF severity is associated with maintained anti-Dsg1 sera levels and its prognosis is unpredictable. MicroRNA (miRNA), dynamic regulators of immune function, have been identified as potential biomarkers for some autoimmune diseases. This study aimed to assess the miRNA expression of miR-17-5p, miR-21-5p, miR-146a-5p, miR-155-5p and miR-338-3p using quantitative real-time PCR in peripheral blood mononuclear cells (PBMC) and lesional skin samples from untreated and treated PF patients (both remittent and chronic) over 3 months. Overall, miRNA expression was significantly higher in PBMC than in biopsy samples. Blood miR-21 expression was increased in untreated patients compared to controls and had a diagnostic value with an AUC of 0.78. After 6 weeks, it decreased significantly, similar to anti-Dsg1 antibodies and the PDAI score. In addition, a positive correlation was observed between cutaneous miR-21 expression and the disease activity score. Conversely, cutaneous expressions of miR-17, miR-146a and miR-155 were significantly higher in treated chronic patients compared to remittent ones. The cutaneous level of miR-155 positively correlated with pemphigus activity, making it a potential predictive marker for patients' clinical stratification with an AUC of 0.86.These findings suggest that blood miR-21 and cutaneous miR-155 can be used as supplemental markers for PF diagnosis and activity, respectively in addition to classical parameters.

Anti-desmoglein 1 antibody-positive mother and antibody-negative child with Darier's disease.

We report a mother and an adult son with Darier's disease. The mother, 76 years old and Japanese, had positivity for anti-desmoglein (Dsg)1 antibodies. She had erythema with hyperkeratosis and seborrheic and interstitial blistering. A high level of anti-Dsg1 antibodies was detected in the serum. Histopathological examination showed acantholysis and direct immunofluorescence testing revealed intercellular IgG and C3 deposition of the epidermis. Although she was diagnosed as having pemphigus foliaceus, the skin lesions slightly improved with immunosuppressive therapy. Her son, 47 years old, had similar skin lesions on the seborrheic and interstitial parts, but the anti-Dsg1 antibodies were negative in his serum. Histopathological examination showed acantholysis and dyskeratotic cells. Although Hailey-Hailey disease was first suspected, no mutation in the ATP2C1 was detected in either patient. Trio-exome analysis including the father showed a heterozygous c.2027C>A transition on exon 14 of ATP2A2, causing a replacement at amino acid 676 (p.Ala676Asp) in the mother and son only. The two patients were then diagnosed as having Darier's disease. Exome analysis further showed that a novel heterozygous missense mutation of DSG1 was identified only in the affected mother. Anti-Dsg1 antibody-positive Darier's disease is reported here for the first time. Very rare coexistence of Darier's disease and anti-Dsg1 antibody-positivity might be associated with this novel heterozygous DSG1 mutation. Experimental evidence is required to validate this hypothesis.

Up-regulation of ST18 in pemphigus vulgaris drives a self-amplifying p53-dependent pathomechanism resulting in decreased desmoglein 3 expression.

Pemphigus vulgaris (PV) is a life-threatening autoimmune mucocutaneous blistering disease which is to a large extent genetically determined, and results, at least in part, from the deleterious activity of autoantibodies directed against desmoglein (DSG)3, a prominent intra-epidermal adhesion molecule. Those autoantibodies lead to decreased membranal DSG3 expression in keratinocytes (KCs), thereby destabilizing cell-cell adhesion within the epidermis and leading to blister formation. We previously showed that rs17315309, a strong risk variant for PV within the promoter of the ST18 transcription factor gene, promotes epidermal ST18 up-regulation in a p53/p63-dependent manner. Accordingly, ST18 was found to be overexpressed in the skin of PV patients. Increased ST18 expression was then shown to markedly augment PV autoantibodies-mediated loss of KCs cohesion. Here, we demonstrate that ST18 overexpression significantly increases autoantibody-mediated DSG3 down-regulation in keratinocytes. In addition, DSG3 decreased expression boosts p53 function through p38 mitogen-activated protein kinase (p38MAPK) activation and dramatically augments p53-dependent ST18 promoter activity. Finally, the PV risk variant rs17315309 is associated with increased p53 expression in PV skin. Taken collectively, these observations reveal a novel self-amplifying pathomechanism involving ST18, DSG3, p38 and p53, capable of perpetuating disease activity, and therefore indicative of novel actionable molecular targets in PV.

The Immunogenetics of Autoimmune Blistering Diseases.

Dermatological conditions constituting the group of autoimmune blistering diseases (AIBD) are characterized by loss of immunotolerance and humoral, as well as cellular, autoimmune responses that result in the development of bullae and erosions on the skin and mucous membranes. AIBDs are broadly categorized into pemphigus and pemphigoid classes with several distinct subtypes amongst them. Advances in genetics have allowed for the study and identification of alleles, and even single nucleotide polymorphisms, that harbor increased susceptibility or confer protection for the development of these conditions. The focus of this chapter pertains to a comprehensive review of the known genetic associations with AIBDs, including HLA class I-III, as well as non-HLA genes and non-coding sequences that influence cellular processes and signaling pathways.

The role of microRNA-338-3p in cancer: growth, invasion, chemoresistance, and mediators.

Cancer still remains as one of the leading causes of death worldwide. Metastasis and proliferation are abnormally increased in cancer cells that subsequently, mediate resistance of cancer cells to different therapies such as radio-, chemo- and immune-therapy. MicroRNAs (miRNAs) are endogenous short non-coding RNAs that can regulate expression of target genes at post-transcriptional level and capable of interaction with mRNA-coding genes. Vital biological mechanisms including apoptosis, migration and differentiation are modulated by these small molecules. MiRNAs are key players in regulating cancer proliferation and metastasis as well as cancer therapy response. MiRNAs can function as both tumor-suppressing and tumor-promoting factors. In the present review, regulatory impact of miRNA-338-3p on cancer growth and migration is discussed. This new emerging miRNA can regulate response of cancer cells to chemotherapy and radiotherapy. It seems that miRNA-338-3p has dual role in cancer chemotherapy, acting as tumor-promoting or tumor-suppressor factor. Experiments reveal anti-tumor activity of miRNA-338-3p in cancer. Hence, increasing miRNA-338-3p expression is of importance in effective cancer therapy. Long non-coding RNAs, circular RNAs and hypoxia are potential upstream mediators of miRNA-338-3p in cancer. Anti-tumor agents including baicalin and arbutin can promote expression of miRNA-338-3p in suppressing cancer progression. These topics are discussed to shed some light on function of miRNA-338-3p in cancer cells.

ST18 affects cell-cell adhesion in pemphigus vulgaris in a tumour necrosis factor-α-dependent fashion.

BACKGROUND: Pemphigus vulgaris (PV) is a life-threatening mucocutaneous autoimmune blistering disease. We previously showed that genetic variants within the ST18 gene promoter area confer a sixfold increase in the propensity to develop PV. ST18, a transcription factor, was found to be overexpressed in the epidermis of patients with PV. In addition, it was found to promote autoantibody-mediated abnormal epidermal cell-cell adhesion and secretion of proinflammatory mediators by keratinocytes. OBJECTIVES: To delineate the mechanism through which ST18 contributes to destabilization of cell-cell adhesion. METHODS: We used quantitative reverse-transcriptase polymerase chain reaction, immunofluorescence microscopy, a luciferase reporter system, site-directed mutagenesis, chromatin immunoprecipitation (ChIP) and the dispase dissociation assay. RESULTS: The ChIP and luciferase reporter assays showed that ST18 directly binds and activates the TNF promoter. Accordingly, increased ST18 expression contributes to PV pathogenesis by destabilizing cell-cell adhesion in a tumour necrosis factor (TNF)-α-dependent fashion. In addition, dual immunofluorescence staining showed increased expression of both ST18 and TNF-α in the skin of patients with PV carrying an ST18-associated PV risk variant, which was found to be associated with a more extensive PV phenotype. CONCLUSIONS: Our findings suggest a role for TNF-α in mediating the deleterious effect of increased ST18 expression in PV skin.

Novel Therapies for Pemphigus Vulgaris.

Pemphigus vulgaris (PV) is a severe chronic autoimmune blistering disease that affects the skin and mucous membranes. It is characterized by suprabasal acantholysis due to disruption of desmosomal connections between keratinocytes. Autoantibodies against desmosomal cadherins, desmoglein 3 and 1, have been shown to induce disease. Certain human leukocyte antigen (HLA) types and non-HLA foci confer genetic susceptibility. Until the discovery of corticosteroids in the 1950s, PV was 75% fatal. Since then, multiple PV treatments, such as systemic corticosteroids and adjunctive therapy with immunosuppressive medications (mycophenolate mofetil, azathioprine, cyclophosphamide, cyclosporine, methotrexate, gold, and others) have been introduced; however, none have led to long-term remissions and many have undesired adverse effects. Our growing understanding of the pathophysiologic mechanisms in PV is leading to development of new targeted therapies, such as intravenous immunoglobulin, anti-CD20 monoclonal antibodies, inhibitors of Bruton tyrosine kinase and neonatal Fc receptors, and adoptive cellular transfer, that may result in lasting control of this life-threatening disease.

Antigen-specific B cell depletion for precision therapy of mucosal pemphigus vulgaris.

Desmoglein 3 chimeric autoantibody receptor T cells (DSG3-CAART) expressing the pemphigus vulgaris (PV) autoantigen DSG3 fused to CD137-CD3ζ signaling domains, represent a precision cellular immunotherapy approach for antigen-specific B cell depletion. Here, we present definitive preclinical studies enabling a first-in-human trial of DSG3-CAART for mucosal PV. DSG3-CAART specifically lysed human anti-DSG3 B cells from PV patients and demonstrated activity consistent with a threshold dose in vivo, resulting in decreased target cell burden, decreased serum and tissue-bound autoantibodies, and increased DSG3-CAART engraftment. In a PV active immune model with physiologic anti-DSG3 IgG levels, DSG3-CAART inhibited antibody responses against pathogenic DSG3 epitopes and autoantibody binding to epithelial tissues, leading to clinical and histologic resolution of blisters. DSG3 autoantibodies stimulated DSG3-CAART IFN-γ secretion and homotypic clustering, consistent with an activated phenotype. Toxicology screens using primary human cells and high-throughput membrane proteome arrays did not identify off-target cytotoxic interactions. These preclinical data guided the trial design for DSG3-CAART and may help inform CAART preclinical development for other antibody-mediated diseases.

Increased expression of miR-338-3p impairs Treg-mediated immunosuppression in pemphigus vulgaris by targeting RUNX1.

Pemphigus vulgaris (PV) is a regulatory T cell (Treg)-associated autoimmune disease. Treg cells maintain immunosuppression by expressing the signature transcription factor FOXP3. MicroRNAs (miRNAs) have frequently emerged as regulators in Treg-mediated immunosuppression. We previously found that miR-338-3p was overexpressed in the peripheral blood mononuclear cells of patients with PV. Herein, we explored the role of miR-338-3p in Treg-mediated immunosuppression by quantitative real-time polymerase chain reaction, analysis of public microarray data, miRNA transfection, Western blotting, flow cytometry, and luciferase reporter assays. Increased expression of miR-338-3p was detected in CD4+ T cells of active PV patients compared with those in healthy controls. Moreover, the miR-338-3p level was positively related to disease severity. Bioinformatics prediction revealed that Runt-related transcription factor 1 (RUNX1), a gene activating FOXP3 expression, was a putative target of miR-338-3p. There was a reduction of FOXP3 and RUNX1 expression in the CD4+ T cells of patients with PV, along with significant correlations with the level of miR-338-3p. MiRNA transfection, mRNA and protein analysis, and luciferase reporter assays verified that miR-338-3p attenuated FOXP3 expression by targeting RUNX1. This study suggests that excessive expression of miR-338-3p attenuates the expression of FOXP3 by targeting RUNX1, contributing to Treg dysfunction in PV.

Common Denominators in the Immunobiology of IgG4 Autoimmune Diseases: What Do Glomerulonephritis, Pemphigus Vulgaris, Myasthenia Gravis, Thrombotic Thrombocytopenic Purpura and Autoimmune Encephalitis Have in Common?

IgG4 autoimmune diseases (IgG4-AID) are an emerging group of autoimmune diseases that are caused by pathogenic autoantibodies of the IgG4 subclass. It has only recently been appreciated, that members of this group share relevant immunobiological and therapeutic aspects even though different antigens, tissues and organs are affected: glomerulonephritis (kidney), pemphigus vulgaris (skin), thrombotic thrombocytopenic purpura (hematologic system) muscle-specific kinase (MuSK) in myasthenia gravis (peripheral nervous system) and autoimmune encephalitis (central nervous system) to give some examples. In all these diseases, patients' IgG4 subclass autoantibodies block protein-protein interactions instead of causing complement mediated tissue injury, patients respond favorably to rituximab and share a genetic predisposition: at least five HLA class II genes have been reported in individual studies to be associated with several different IgG4-AID. This suggests a role for the HLA class II region and specifically the DRß1 chain for aberrant priming of autoreactive T-cells toward a chronic immune response skewed toward the production of IgG4 subclass autoantibodies. The aim of this review is to provide an update on findings arguing for a common pathogenic mechanism in IgG4-AID in general and to provide hypotheses about the role of distinct HLA haplotypes, T-cells and cytokines in IgG4-AID.

Single-nucleotide polymorphisms associated with pemphigus vulgaris: Potent markers for better treatment and personalized medicine.

Pemphigus vulgaris (PV) is a rare autoimmune blistering disorder, which could affect both skin and mucosal surfaces. There is increasing evidence that genetics plays a critical role in PV development, severity and prognosis. Single-nucleotide polymorphisms (SNPs) are the most common type of genetic variation among people and have been widely evaluated in most diseases. However, there are few studies regarding the roles of SNPs in the PV. Here, we reviewed both pathogenic and protective roles of the SNPs in non-HLA genes regarding the PV. Among the large number of studied SNPs, it was found that several SNPs in different genes might control the susceptibility of PV, including TNFA (rs361525, rs1800629, rs1800629), IL10 (rs1800871, rs1800896, rs1800871, and rs1800872), IL6 (rs1800795), CTLA4 (rs231775), ICOS (rs10932029), CD86 (rs1129055), DSG3 (rs8085532, rs3911655, rs3848485, rs3794925, rs1466379), ST18 (rs2304365, rs17315309) and TAP2 (rs7454108), probably in a population-specific manner. Moreover, SNPs in glucocorticoid receptor, also known as nuclear receptor subfamily 3 group C member 1 (NR3C1) gene, including rs11745958, rs17209237, rs33388, rs7701443 as well as rs116855232 at NUDT15, seem to be associated with therapeutic outcomes in PV patients. Additionally, variations in the other genes involved in the drugs' metabolisms, pharmacokinetics and pharmacodynamics such as rs396991 in FCGR3A gene could be used for the prediction of clinical response to drugs and side effects. Taken together, SNPs seem to be valuable tools for better management of PV patients. Further studies need to be conducted to evaluate SNPs in genes that control immune responses and apoptosis.

FMF Is Associated With a Wide Spectrum of MHC Class I- and Allied SpA Disorders but Not With Classical MHC Class II-Associated Autoimmune Disease: Insights From a Large Cohort Study.

Objectives: To test the hypothesis that familial Mediterranean fever (FMF)-associated autoinflammation may exaggerate the tendency toward adaptive immunopathology or spondyloarthritis (SpA)-associated disorders including major histocompatibility complex (MHC) class I associated disorders but not classical MHC class II-associated disorders that exhibit transplacental autoimmunity including myasthenia gravis and pemphigus. Methods: Seven thousand seven hundred forty-seven FMF patients and 10,080 age- and sex-matched controls in the Clalit Health Services medical database were identified and compared in terms of prevalence of SpA-associated disorders. We also evaluated four classical and strong MHC class II-associated disorders, namely, pemphigus vulgaris, myasthenia gravis, sarcoidosis, and pernicious anemia, to ascertain whether such associations with SpA-spectrum disease were specific or merely reflected the non-specific consequences of innate immune system activation on driving divergent types of immunity. The diagnosis of FMF was based on the medical records and not genetically proven. Results: FMF showed a strong association with MHC class I-related diseases: odds ratio (OR) of 28.58 [95% confidence interval (95% CI), 6.93-117.87; p < 0.0001] for Behçet's disease, OR of 10.33 (95% CI, 4.09-26.09; p < 0.0001) for ankylosing spondylitis, and OR of 1.67 (95% CI, 1.19-2.33; p = 0.0029) for psoriasis. For weakly MHC class I-linked diseases, an OR of 3.76 (95% CI, 2.48-5.69; p < 0.0001) for Crohn's disease and OR of 2.64 (95% CI, 1.52-4.56; p = 0.0005) for ulcerative colitis were found. No association was found between FMF and the four MHC class II-associated autoimmune disorders. Conclusion: FMF patients are associated with increased risk of SpA-related disease diagnosis including MHC-I-opathies but not MHC-II-associated autoimmune diseases, suggesting that tissue-specific dysregulation of innate immunity share between FMF and SpA spectrum disorders may drive adaptive immune MHC class I-associated conditions.

Condemned or Not to Die? Gene Polymorphisms Associated With Cell Death in Pemphigus Foliaceus.

Pemphigus foliaceus (PF) is an autoimmune blistering skin disease that occurs sporadically across the globe and is endemic in Brazil. Keratinocyte adhesion loss (acantholysis) is associated with high levels of anti-desmoglein 1 IgG autoantibodies, but the role of cell death is poorly understood in PF. Current evidence disqualifies apoptosis as the major cell death mechanism and no other process has yet been investigated. To approach the role of variation in genes responsible for cell death pathways in pemphigus susceptibility, we systematically investigated the frequencies of 1,167 polymorphisms from genes encoding products of all 12 well-established cell death cascades (intrinsic and extrinsic apoptosis, necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic, NETotic, lysosome-dependent, autophagy-dependent, and immunogenic). By multivariate logistic regression, we compared allelic and genotypic frequencies of 227 PF patients and 194 controls obtained by microarray hybridization. We found 10 variants associated with PF (p < 0.005), belonging to six cell death pathways: apoptosis (TNF, TRAF2, CD36, and PAK2), immunogenic cell death (EIF2AK3, CD47, and SIRPA), necroptosis (TNF and TRAF2), necrosis (RAPGEF3), parthanatos (HK1), and pyroptosis (PRKN). Five polymorphisms were associated with susceptibility: TNF rs1800630*A (OR = 1.9, p = 0.0003), CD36 rs4112274*T (OR = 2.14, p = 0.0015), CD47 rs12695175*G (OR = 1.77, p = 0.0043), SIRPA rs6075340*A/A (OR = 2.75, p = 0.0009), and HK1 rs7072268*T (OR = 1.48, p = 0.0045). Other five variants were associated with protection: TRAF2 rs10781522*G (OR = 0.64, p = 0.0014), PAK2 rs9325377*A/A (OR = 0.48, p = 0.0023), EIF2AK3 rs10167879*T (OR = 0.48, p = 0.0007), RAPGEF3 rs10747521*A/A (OR = 0.42, p = 0.0040), and PRKN rs9355950*C (OR = 0.57, p = 0.0004). Through functional annotation, we found that all associated alleles, with the exception of PRKN rs9355950*C, were previously associated with differential gene expression levels in healthy individuals (mostly in skin and peripheral blood). Further functional validation of these genetic associations may contribute to the understanding of PF etiology and to the development of new drugs and therapeutic regimens for the disease.

Long noncoding RNA polymorphisms influence susceptibility to endemic pemphigus foliaceus.

BACKGROUND: Pemphigus foliaceus (PF) is an epidermal autoimmune disease, characterized by the presence of autoantibodies against the desmosomal protein desmoglein 1. Genetic and environmental factors contribute to PF, a complex disease that is endemic in Brazil and Colombia and neighbouring countries, and in Tunisia. Long noncoding RNAs (lncRNAs) may participate in gene regulation by interacting with DNA, proteins and other RNAs. Dysregulation of lncRNAs has recently been recognized as an important coplayer in the onset or progression of complex diseases. In addition, single-nucleotide polymorphisms (SNPs) located in lncRNA genes have been associated with differential risk to cancer, autoimmunity and infection. OBJECTIVES: Here, we aimed to investigate whether SNPs in lncRNA genes are associated with differential susceptibility to endemic PF. MATERIALS AND METHODS: We integrated data from the lncRNA SNP database with genome-wide genotype data obtained for 229 patients and 6681 controls. We tested the association between endemic PF and 2080 SNPs located in lncRNAs applying logistic regression. RESULTS: The most significantly associated SNP was rs7144332 (OR = 1·63, P = 2·8 × 10-6 ), located in the lncRNA gene AL110292·1. Results for five other SNPs were suggestive of association (P < 0·001). In silico analysis indicated that five of the six SNPs impact transcription, three may influence lncRNA's secondary structure, and three may alter microRNA-lncRNA interactions. CONCLUSIONS: We showed, for the first time, that variation in lncRNA genes may influence pemphigus pathogenesis. Our findings highlight the importance of lncRNA variation in autoimmune and possibly other complex diseases and suggest polymorphisms for functional validation.

Subtype-specific inherited predisposition to pemphigus in the Chinese population.

BACKGROUND: Pemphigus is a group of rare life-threatening mucocutaneous autoimmune diseases, presenting mainly as two subtypes: pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Inherited predispositions to pemphigus have long been speculated but they remain poorly understood. OBJECTIVES: To identify common and specific nongenetic and genetic factors associated with pemphigus and its subtypes in the Chinese population. METHODS: A genome-wide association study (GWAS) was performed in 496 unrelated patients with pemphigus (including 365 with PV and 104 with PF) and 1105 controls without pemphigus. RESULTS: A sex preference was observed only in PV (57·5% female) and not in PF (47·1% female). For male patients only, the mean age at diagnosis was significantly lower for PV than for PF (P < 0·001). The strongest associated single-nucleotide polymorphisms are in the human leucocyte antigen (HLA) region: rs70993900 (PV; P = 1·5 × 10-45 ) and rs9469220 (PF; P = 1·1 × 10-8 ). HLA-DQB1*05:03 ranks at the top (P = 4·7 × 10-40 ; odds ratio 12·4) in both subtypes, with significantly different risk allele frequency (RAFPV = 34·2% vs. RAFPF = 18·8% vs. RAFcontrol = 4·4%), whereas HLA-DRB1*14:01 and HLA-DRB1*04:06 are PV specific. HLA-DQB1*03:03 and HLA-DQB1*03:02 show significant subtype specificity in opposite directions. All of these associations were validated in the replication series with 147 cases of pemphigus and 604 controls. Multiple novel non-HLA susceptibility loci were also identified in the GWAS. CONCLUSIONS: This study represents the largest GWAS on pemphigus in the Chinese population published to date, and has allowed us to identify HLA haplotypes significantly shared between or specific to the two main subtypes of pemphigus.