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Mucous membrane pemphigoid (MMP) is an autoimmune subepithelial/subepidermal blistering disease characterized by linear deposition of immunoglobulin G (IgG), IgA, and/or C3 in the basement membrane zone (BMZ) and predominant mucosal lesions involving the oral cavity and conjunctivae. Here, we describe a case of a 58-year-old Japanese man with MMP. Intraoral examination revealed desquamative gingivitis in the upper and lower gingivae. No conjunctival or cutaneous lesions were observed. Histopathological examination revealed a subepithelial split with inflammatory cell infiltration of the epithelial and connective tissues. Direct immunofluorescence revealed a linear deposition of C3 in the BMZ. IgG autoantibodies against BP230 were detected using an enzyme-linked immunosorbent assay. Indirect immunofluorescence using 1mol/L NaCl-split skin sections revealed no reactivity for serum IgG or IgA. Immunoblotting using normal human epidermal extract as a substrate did not detect IgG reactivity against the 230-kDa antigen. Based on the above results, the definitive diagnosis of MMP with anti-BP230 antibody alone was established. Our case was categorized as low-risk MMP. The patient was treated with 0.1% triamcinolone acetonide ointment, oral minocycline, and oral nicotinamide, which improved the oral erosions. However, the mechanism underlying IgG autoantibody production against intracellular BP230 remains unclear. Further research and more such case studies are necessary to elucidate the mechanism of anti-BP230 antibody production and the clinical feature of anti-BP230 type MMP.

Vancomycin (VCM) is known to induce linear IgA bullous dermatosis (LAD). However, in contrast to conventional LAD, in which circulating IgA autoantibodies against basement membrane proteins are commonly detected, patient sera from VCM-induced LAD yields negative results in indirect immunofluorescence microscopy, and the targeted autoantigen remains undetermined. By using sera from a typical patient with VCM-induced LAD, we identified that co-incubation of sera with VCM resulted in linear IgA deposition at the basement membrane zone by indirect immunofluorescence. Patient sera reacted with the dermal side of 1 mol/L NaCl-split skin and with the recombinant noncollagenous (i.e., NC1) domain of type VII collagen by both immunoblot and ELISA in the presence of VCM. The investigation of an additional 13 patients with VCM-induced LAD showed that 10 out of the 14 sera (71.4%) reacted with the NC1 domain of type VII collagen by ELISA when spiked with VCM, whereas only 4 (28.6%) tested positive without it. The enhancement of reactivity to NC1 by VCM, as determined by optical density via ELISA, was observed in 10 out of the 14 sera (71.4%). These findings indicate that type VII collagen is a target autoantigen in VCM-induced LAD and that VCM mediates IgA autoreactivity against type VII collagen, providing an insight into mechanisms involved in drug-induced autoimmune disease.

IMPORTANCE: Enzyme-linked immunosorbent assay (ELISA) and/or chemiluminescent enzyme immunoassay (CLEIA) for BP180 noncollagenous 16A (NC16A) extracellular domain is a sensitive diagnostic tool for bullous pemphigoid (BP). However, some patients with BP have negative results for these assays. OBJECTIVE: To elucidate the clinical and immunological features of patients with BP without antibodies that react to BP180 NC16A. DESIGN, SETTING, AND PARTICIPANTS: This retrospective case series study included 152 patients who were diagnosed with BP and followed up at the Kurume University Hospital in Japan from 2007 to 2016. The diagnosis was made using clinical, histological, and immunological findings. MAIN OUTCOMES AND MEASURES: Clinical and immunological features of patients with BP who had negative results for BP180 NC16A using ELISA and/or CLEIA. RESULTS: Of the 152 patients, 69 (45.4%) were men and 83 (54.6%) were women. The mean (SD) age of participants was 75.2 (14.4) years. Of the 152 patients with BP, 14 (9.2%) had negative results for BP180 NC16A on ELISA and/or CLEIA; most of these patients exhibited no erythema and had relatively mild phenotypes. Two (14%) of the 14 patients had positive results for intact BP180 in epidermal extracts, 10 (71%) had positive results for a 120-kD fragment of BP180 (LAD-1) and 3 (21%) had positive results for BP180 C-terminal domain. Seven (50%) patients tested positive in BP230 ELISA. Five (36%) patients did not require oral prednisolone treatment, whereas the others required a dose of prednisolone at less than 30 mg per day. Three (21%) patients were administered a dipeptidyl peptidase-4 inhibitor (DPP4i) before disease onset. This ratio was not significantly higher than that in patients with BP who tested positive for BP180 NC16A ELISA and/or CLEIA (19 [14%] of 138 patients). Our follow-up study (mean [SD], 31.9 [33.2] weeks; range, 0-108 weeks) revealed that patients with BP tested negative for BP180 NC16A ELISA and/or CLEIA during the later stages of the disease. CONCLUSIONS AND RELEVANCE: This study indicates that patients with BP negative for BP180 NC16A ELISA and/or CLEIA had milder phenotypes, fewer erythemas, and required less extensive treatments.

All plakin family proteins are known to be autoantigens in paraneoplastic pemphigus (PNP). In this study, we first examined whether PNP sera also react with epiplakin, another plakin protein, by various immunological methods using 48 Japanese PNP sera. Immunofluorescence confirmed that cultured keratinocytes expressed epiplakin. Epiplakin was detected by 72.9% of PNP sera by immunoprecipitation-immunoblotting with KU-8 cell extract, but not by immunoblotting of either normal human epidermal extract or KU-8 cell extract. Epiplakin was essentially not detected by 95 disease and normal control sera. Statistical analyses of various clinical and immunological findings revealed a significant correlation of the presence of anti-epiplakin antibodies with both bronchiolitis obliterans and mortality. No epiplakin-negative PNP case developed bronchiolitis obliterans. However, although 29.4% of European patients with PNP had bronchiolitis obliterans, significant correlation with anti-epiplakin autoantibodies was not observed. In further studies for lung, immunofluorescence showed the presence of epiplakin in normal human lung, particularly respiratory bronchiole, immunoprecipitation-immunoblotting showed that PNP sera reacted with epiplakin in cultured lung cells, and mice injected with polyclonal antibody specific to epiplakin histopathologically showed abnormal changes in small airway epithelia. These results indicated that epiplakin is one of the major PNP autoantigens and is related to PNP-related bronchiolitis obliterans.

Linear IgA bullous dermatosis is characterized by IgA autoantibodies reactive with LAD-1 and LABD97, truncated forms of BP180 (type XVII collagen), but not with full-length BP180. Toyonaga et al. determined that cleavage within both the C-terminal region and NC16A domain plays a role in exposure of neoepitopes on the 15th collagenous domain of BP180.

The patient was a 47-year-old female who presented with skin and oral mucosal lesions. Edematous erythema and pigmentation with crusts were observed on the sinciput, precordium and upper back, and gingival erosion and redness were seen in the oral cavity. Clinically, pemphigus vulgaris (PV) was suspected. However, blood examination results were positive for antidesmoglein 1 antibody, but negative for anti-Dsg 3 antibody. Histopathological examination and direct immunofluorescence microscopic observation revealed superficial vesicular formation and IgG and C3 deposits in the epithelial cell membranes. A diagnosis of pemphigus foliaceus (PF) was made. Regarding the gingival lesions, histopathological cleavage of the suprabasal cell layer was detected, and direct immunofluorescence microscopy found intercellular IgG and C3 deposits in almost the entire epithelial cell layer. These findings were compatible with PV. As there was a contradiction between the clinical features and laboratory data, we further performed immunoblotting analysis. Autoantibodies against periplakin and C-terminal of the 180-kDa bullous pemphigoid antigen (BP 180) were detected. However, these autoantibodies were not considered to pathogenic. We report a rare case of anti-Dsg 1 antibody-positive and anti-Dsg 3 negative pemphigus with oral mucosal lesions.

IMPORTANCE Linear IgA/IgG bullous dermatosis (LAGBD) is a relatively rare autoimmune bullous disease characterized by both IgA and IgG antibodies to epidermal basement membrane zone. The heterogeneity and pathogenesis of the LAGBD autoantigens have not been fully elucidated. OBSERVATIONS We report 3 Japanese cases of LAGBD (ages 81, 88, and 64 years; 1 woman and 2 men). The patients showed bullous and erosive lesions on the trunk and extremities with minimal mucosal lesions. Histopathological analysis revealed a subepidermal blister with neutrophilic infiltration with eosinophils in 2 cases. Direct and indirect immunofluorescence studies disclosed IgG and IgA antibasement membrane zone antibodies. In immunoblot analyses of various antigen sources, all cases showed IgG and IgA antibodies to various subunits of laminin-332, in addition to IgG and IgA reactivity with type VII collagen, laminin-γ1, and BP230 and BP180 recombinant proteins. CONCLUSIONS AND RELEVANCE Our studies revealed that the 3 LAGBD cases showed prominent IgG and IgA reactivity with laminin-332, which was only rarely reported. In addition, all cases showed IgG and IgA reactivity with other multiple antigens, indicating the role of epitope-spreading mechanisms initiated from laminin-332. The significance of IgA antibodies to laminin-332 should be studied in larger cohorts of both LAGBD and linear IgA bullous dermatosis.

IMPORTANCE Pemphigus vegetans shows clinically vegetating and/or pustular skin lesions mainly on the intertriginous areas and histopathologically neutrophilic and eosinophilic pustules in the epidermis. Pemphigus vegetans shows IgG reactivity mainly with desmoglein (Dsg) 3, but also with other autoantigens, including Dsg1 and desmocollins (Dscs). OBSERVATIONS We examined antigen profiles in 2 cases of pemphigus vegetans. (1) A women in her 80s presented with typical vegetating skin lesions on the right inguinal region with typical histopathological features. Immunoblotting using normal human epidermal extracts detected IgG antibodies to Dsg1 and Dscs. Enzyme-linked immunosorbent assays (ELISAs) revealed IgG antibodies to Dsg1 but not to Dsg3. Complementary DNA (cDNA) transfection method to COS-7 cells and novel ELISAs using eukaryotic recombinant proteins of human Dsc1, Dsc2, and Dsc3 confirmed specific IgG reactivity with Dsc3. (2) A women in her 70s presented with pustular skin lesions on the left fingers with typical histopathological features. Immunoblotting and ELISAs did not detect antibodies to either Dsg1 or Dsg3. Conversely, immunoblotting detected IgG antibodies to Dscs, cDNA transfection method revealed IgG reactivity only with Dsc3, and findings from ELISAs showed that IgG reacted weakly with Dsc2 and strongly with Dsc3. CONCLUSIONS AND RELEVANCE Autoantibodies to Dscs, particularly to Dsc3, may play a pathogenic role in some cases of pemphigus vegetans.

Introduction:Desmoglein 3 (Dsg3) is one of desmosomal cadherins and functions in epidermal keratinocyte adhesion. IgG anti-Dsg3 autoantibodies are detected in pemphigus vulgaris, an autoimmune bullous disease showing blisters and erosions on the skin and oral mucosa. Other types of pemphigus also show anti-Dsg3 antibodies. Genetic disease of Dsg3 has not been reported.Areas covered:Many in vitroand in vivostudies have indicated pathogenic role of anti-Dsg3 antibodies. Blisters in pemphigus vulgaris are thought to be developed by loss of keratinocyte adhesions by binding of anti-Dsg3 antibodies to Dsg3 through steric hindrance, internalization of Dsg3, changes in molecular integrity or signal transduction. There are pathogenic and nonpathogenic anti-Dsg3 antibodies reactive with different epitopes. Recent studies of pemphigus vulgaris include existence of non-Dsg3 autoantibodies, B cells and T cells reactive with Dsg3, involvement of TNF-α and IL-1 and activation of intracellular signaling.Expert opinion:Although systemic corticosteroids and immunosuppressive agents are mainstays for treatment of pemphigus, intravenous immunoglobulin, plasmapheresis, immunoadsorption, rituximab and TNF-α inhibitors are emerging. Anti-Dsg3 antibody-targeting therapies are reported in mouse model, but they are not yet available clinically. Clarification of pathogenic role of anti-Dsg3 antibodies in pemphigus should provide us with safer and more effective therapies.

BACKGROUND Anti-p200 pemphigoid is a rare autoimmune subepidermal blistering disorder. Clinically, it may resemble bullous pemphigoid, linear IgA bullous dermatosis, or dermatitis herpetiformis. Immunologically, anti-p200 pemphigoid is characterized by the development of IgG antibodies directed against a basement membrane zone protein with a molecular weight of 200 kDa. OBSERVATIONS We report the first case, to our knowledge, of anti-p200 pemphigoid associated with IgA antibodies and having clinical features resembling pemphigus herpetiformis or dermatitis herpetiformis localized on traumatized areas. Histopathological examination of lesional skin showed dermal-epidermal separation and microabscesses composed of neutrophils in the dermal papillae. Direct immunofluorescence disclosed the presence exclusively of linear in vivo –bound IgA along the basement membrane zone. With the use of laser scanning confocal microscopy, in vivo –bound IgA was localized above collagen type IV and colocalized with laminin 332. Indirect immunofluorescence showed circulating IgA antibodies against basement membrane zone at a titer of 1:160 that reacted with the floor of an artificial blister of salt-split skin. Western immunoblot analysis using dermal extract confirmed the reactivity of circulating IgA antibodies with the 200-kDa antigen corresponding to laminin γ1; however, immunoblotting using recombinant protein of 107 amino acid C-terminus of laminin γ1 was negative for circulating IgA antibodies. Immunoelectron microscopy disclosed the reactivity of circulating IgA autoantibodies within the lower lamina lucida. CONCLUSION To the best of our knowledge, this is the first case fulfilling the immunopathological criteria for anti-p200 pemphigoid associated with IgA antibodies and having unusual clinical features.

Pemphigus is considered an autoimmune bullous skin disorder associated with IgG against the desmosomal components, desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1). This concept is supported by the in vitroand in vivopathogenicity of anti-Dsg3/Dsg1 IgG and the mucosal blistering phenotype of mice with a genetic deficiency of Dsg3. Mice deficient for another desmosomal adhesion molecule, desmocollin 3 (Dsc3), show a similar pemphigus phenotype, and we investigated the pathogenicity of Dsc3-reactive IgG autoantibodies that were identified previously in a subset of patients with atypical pemphigus. We here demonstrate that IgG against Dsc3 causes loss of adhesion of epidermal keratinocytes. Specifically, IgG against Dsc3 was purified from Dsc3-reactive pemphigus sera by affinity column chromatography using recombinant human Dsc3. Affinity purified IgG was functionally active and did not only react with recombinant Dsc3 but also with epidermis and cultured human keratinocytes. Moreover, Dsc3-reactive IgG induced loss of adhesion of epidermal keratinocytes in a dispase-based keratinocyte dissociation assay that was reversed on pre-adsorption with human Dsc3 but not Dsg3. These findings demonstrate that IgG autoantibodies against an additional component of the desmosomes, Dsc3, induce loss of keratinocyte adhesion and thus may contribute to blister formation in pemphigus.

Pemphigus vulgaris is a blistering disease associated with autoantibodies to the desmosomal adhesion protein, desmoglein 3. Genetic deficiency of desmoglein 3 in mice mimics autoimmunity to desmoglein 3 in pemphigus vulgaris, with mucosal-dominant blistering in the suprabasal layer of the epidermis. Mice with an epidermal-specific deletion of desmocollin 3, the other major desmosomal cadherin isoform expressed in the basal epidermis, develop suprabasal blisters in skin that are histologically identical to those observed in pemphigus vulgaris, suggesting that desmocollin 3 might be a target of autoantibodies in some pemphigus vulgaris patients. We now demonstrate that desmocollin 3 is an autoantigen in pemphigus vulgaris, illustrated in a patient with mucosal-dominant blistering. Six of 38 pemphigus vulgaris and one of 85 normal serum samples immunoprecipitate desmocollin 3 (P= 0.003). Incubation of patient IgG with human keratinocytes causes loss of intercellular adhesion, and adsorption with recombinant desmocollin 3 specifically prevents this pathogenic effect. Additionally, anti-desmocollin 3 sera cause loss of keratinocyte cell surface desmocollin 3, but not desmoglein 3 by immunofluorescence, indicating distinct cellular pathogenic effects in anti-desmocollin and anti-desmoglein pemphigus, despite their identical clinical presentations. These data demonstrate that desmocollin 3 is a pathogenic autoantigen in pemphigus vulgaris and suggest that pemphigus vulgaris is a histological reaction pattern that may result from autoimmunity to desmoglein 3, desmocollin 3, or both desmosomal cadherins.

Bullous pemphigoid (BP) associated with milia lesions has been increasingly reported, but its prevalence has not been reported in a Brazilian BP population yet.

Bullous pemphigoid (BP) is an acquired autoimmune blistering disease which predominantly affects the elderly. It is rare in children and infants. We reported a 14‐year‐old girl presenting with a month history of relapsing tense bullae on the face and extremities. Histopathological examination of the lesional skin revealed a subepidermal bulla with infiltration of eosinophils, neutrophils, and lymphocytes. Direct immunofluorescence showed linear deposits of IgM and C3 at the basement membrane zone. Indirect immunofluorescense using normal human skin sections as a substrate detected IgG anti‐basement membrane zone antibodies in the patient's serum and that using 1M NaCl split skin sections showed that the patient's antibodies bound to the epidermal side of the split skin. Immunoblot analysis using normal human epidermal extracts demonstrated the presence of autoantibodies against the 230‐kDa BP antigen. Furthermore, the patient's serum reacted with the recombinant protein of the NC16a domain of the 180‐kDa BP antigen by immunoblot analysis and enzyme‐linked immunosorbent assay. Our patient showed significant improvement of the skin lesions with systemic administration of diaminodiphenyl sulfone.

Pemphigus is a group of autoimmune bullous diseases characterized by the presence of autoantibodies against adhesion molecules, desmogleins, and desmocollins (DSCs). The pathogenicity of anti-DSC3 antibodies in pemphigus has been demonstrated; however, its characteristics have not yet been elucidated. We aimed to analyze the characteristics of anti-DSC3 antibodies using DSC3 domain‒swapped desmoglein 2 molecules in which the prosequence and five extracellular (EC) domains of desmoglein 2 were replaced with the corresponding domains of human DSC3. Using these proteins, we established an ELISA and analyzed sera from 56 patients with pemphigus. In 34 pemphigus sera positive for DSC3 full-EC domains, 15 sera (44.1%) were positive for EC2 domain, whereas other domains were rarely positive. We assessed the reactivity to a calcium-dependent epitope in DSC3 by ELISA with EDTA. The reactivity with the EC2 domain was mostly compromised in the presence of EDTA. In the in vitro assay, IgG from patients with paraneoplastic pemphigus preadsorbed with EC2 prevented both reduction of DSC3 and keratinocyte dissociation as compared with that with EDTA-treated EC2. This study revealed a predominant recognition of calcium-dependent epitopes in EC2 domain by anti-DSC3 antibodies and its pathogenicity on keratinocyte adhesion through DSC3 depletion.