The transition of pemphigus vulgaris into pemphigus foliaceus: a reflection of changing desmoglein 1 and 3 autoantibody levels in pemphigus vulgaris

The transition of pemphigus vulgaris (PV) into pemphigus foliaceus (PF) is rare and the immunological changes underlying this event are not well understood. We report a 44-year-old woman who presented with oral and cutaneous erosions typical of PV. Over a 9-year period, the clinical features evolved into those of PF. To examine whether quantitative changes in desmoglein (Dsg) antibodies were associated with this transition, Dsg1 and Dsg3 antibody levels were measured by enzyme-linked immunosorbent assay in 82 sequential serum samples collected over this period. At presentation, when the phenotype was PV with oral and cutaneous erosions, antibodies to both Dsg1 and Dsg3 were detected. The disappearance of oral involvement was associated with a decline in Dsg3 antibodies, which are now undetectable, while the development of more severe skin involvement was associated with rising Dsg1 antibody levels. These data strongly suggest that the change in clinical features is a reflection of qualitative and quantitative changes in antibody profile. It is not known whether the transition to PF is permanent or whether disease relapses in the future may be associated with the re-emergence of Dsg3 antibodies, oral ulceration and a PV phenotype.     

The severity of cutaneous and oral pemphigus is related to desmoglein 1 and 3 antibody levels

BACKGROUND: Pemphigus vulgaris (PV) and foliaceus (PF) are characterized by antibodies to the desmosomal proteins desmoglein 3 (Dsg3) and desmoglein 1 (Dsg1), respectively. Past studies using indirect immunofluorescence (IIF) as a measure of pemphigus antibody levels have failed to demonstrate consistently a relationship between disease severity and IIF titres. However, IIF is not able to measure separately Dsg1 and 3 antibodies, unlike enzyme-linked immunosorbent assays (ELISA), which utilize recombinant proteins. OBJECTIVES: To compare independently Dsg1 and 3 antibody levels with the severity of both cutaneous and oral involvement in PV and PF. Patients and methods Four hundred and twenty-four serum samples were analysed from 80 subjects with PV and 24 with PF. IgG antibodies to Dsg1 and 3 were measured by ELISA. For every sample analysed, the associated severity of skin and oral disease were graded from 0 to 3; quiescent, mild, moderate and severe. RESULTS: A relationship between Dsg1 antibodies and skin severity was demonstrated such that a 10-unit increase in Dsg1 ELISA value was associated with a 34% chance of having a higher severity score [95% confidence interval (CI), 25-45%, P < 0.0005]. This was observed in both PV and PF. Oral severity was associated with Dsg3 antibody levels and a 10-unit increase in the Dsg3 ELISA value was associated with a 25% chance of a higher oral severity score (CI 17-33%, P < 0.0005). We were unable to demonstrate a relationship between Dsg1 antibodies and oral severity, even after adjusting for the effect of Dsg3 antibodies. Similarly, there was no relationship between Dsg3 antibodies and skin severity. CONCLUSIONS: This study suggests that the clinical phenotype of pemphigus, in particular the balance of skin and oral disease, is determined principally by the quantities of Dsg1 and 3 autoantibodies, respectively.     

Cutaneous pemphigus vulgaris with absence of desmoglein 1 autoantibodies. An example of the extended desmoglein compensation theory

A 79 year‐old male patient presented clinically as a typical case of pemphigus foliaceus. He displayed a seborrhoeic pattern of crusting and erosions with an absence of oral involvement. Surprisingly, a biopsy showed suprabasilar acantholysis and direct immunofluorescence consistent with pemphigus vulgaris. Indirect pemphigus antibodies were positive for desmoglein 3 (DSG‐3) but negative for DSG‐1 antibodies. Most cases of cutaneous pemphigus are reported to have both DSG‐1 and DSG‐3 antibodies. A rare cutaneous subtype of pemphigus vulgaris is reported in the literature that may present clinically as seen in our patient. Our patient is clinically similar to these previous reported cases but with a negative DSG‐1 antibody titre. The extended DSG compensation theory explains the differences of clinical expression in pemphigus based on the variable pathogenicity of DSG antibodies as well as the distribution of DSG‐1 and DSG‐3. We discuss this case, highlighting the theories of the pathogenesis of pemphigus and, in particular, the cutaneous pemphigus subtype.     

The clinical transition between pemphigus foliaceus and pemphigus vulgaris correlates well with the changes in autoantibody profile assessed by an enzyme-linked immunosorbent assay

BACKGROUND: There are a number of reports of pemphigus with clinical shifting between pemphigus foliaceus (PF) and pemphigus vulgaris (PV). On the other hand, a novel enzyme-linked immunosorbent assay (ELISA) against recombinant baculoproteins of desmoglein 1 (Dsg1) (PF antigen) and Dsg3 (PV antigen) has been established and found to be extremely sensitive and specific. OBJECTIVES: To characterize the change in the antibody profiles in a series of pemphigus cases with mixed features of PF and PV by various methods, including the novel ELISA. Patients/methods Sera were obtained from eight cases undergoing a shift between PF and PV and three cases of coexistent PF and PV. The autoantigens were analysed by ELISA, as well as by immunofluorescence using normal human skin sections and immunoblotting using normal human epidermal extracts. RESULTS: The results of the ELISA, immunofluorescence and immunoblotting studies showed that the transition between PF and PV correlates well with the changes of autoantibodies against either Dsg1 or Dsg3. CONCLUSIONS: The clinical phenotype at each stage is defined by the anti-Dsg antibody profile in the serum of these pemphigus patients showing mixed features of PF and PV. In addition, ELISA using recombinant baculoproteins was particularly useful in distinguishing PF and PV.     

Cleavage of desmoglein 3 can explain its depletion from keratinocytes in pemphigus vulgaris

We have previously demonstrated that serum of patients with pemphigus vulgaris induces reduction of desmoglein 3 (Dsg3) half-life in keratinocytes (FEBS Lett 2006: 580: 3276). This phenomenon seems to occur as a consequence of the progressive depletion of Dsg3 from desmosomes. Here we reported that reduction of full-length Dsg3 may be due to its progressive cleavage, leading to the formation of two fragmentation products with apparent molecular masses of about 60 kDa (fragment 1) and 70 kDa (fragment 2), as revealed by Western blotting. Unexpectedly, analysis of fragmentation pattern suggested cleavage to occur intracellularly. Consistently, fragment 1 was shed and localized within the cytosol, as shown by living cell immunofluorescence microscopy. Total amounts of full-length plakoglobin and Dsg1 were apparently unchanged. Taken together, our findings provide evidence that proteolytic processing of Dsg3 can lead to depletion of Dsg3 from the cell.     

Immune response towards the amino‐terminus of desmoglein 1 prevails across different activity stages in nonendemic pemphigus foliaceus

Background Pemphigus foliaceus (PF) is a blistering skin disease mediated by antibodies to desmoglein (Dsg) 1. The two major subtypes are nonendemic and endemic PF. A previous study in endemic PF demonstrated that changes in antibody epitope could modulate disease relapse and remission. Objectives To characterize the frequency of immunoreactivity to various Dsg1 extracellular (EC) domains in nonendemic PF and to study if there is any change in epitope profile across various activity stages. Methods Sera from 34 patients with nonendemic PF were selected. To map the conformational epitopes by immunoprecipitation‐immunoblotting, we constructed five Dsg1/Dsg2 domain‐swapped molecules, with each molecule representing one EC domain of Dsg1 on a backbone of Dsg2. Results Dsg1 EC1, EC2, EC3, EC4 and EC5 domains were recognized by 88%, 50%, 13%, 22% and 0% of active PF sera, respectively. Immunoreactivity to EC3 or EC4 often cosegregated with that to either EC1 or EC2. Longitudinal follow‐up of 21 patients with PF for a median of 16 months revealed that, in most cases, immunoreactivity to the amino‐terminus of Dsg1 persisted across various activity stages; only two patients lost their EC1 reactivity upon remission and changed their major epitope(s) to EC2 ± EC3. Conclusions Most of the anti‐Dsg1 antibodies in nonendemic PF bind to the amino‐terminus of Dsg1, a region critical for intercellular adhesion of cadherins, and this skewed amino‐terminal immunoreactivity prevails across various activity stages in most patients, even upon remission. These findings are valuable for understanding the biology of Dsg‐mediated cellular adhesion as well as for the development of epitope‐based monitoring and therapeutic strategies.     

Comparison of desmoglein ELISA and indirect immunofluorescence using two substrates (monkey oesophagus and normal human skin) in the diagnosis of pemphigus

A prospective study was performed to assess the usefulness of desmoglein enzyme-linked immunosorbent assay testing compared with indirect immunofluorescence in the diagnosis of new cases of pemphigus, as well as to compare the relative sensitivities of monkey oesophagus and normal human skin as substrates for indirect immunofluorescence. These tests were performed on the sera of 29 consecutive new cases of pemphigus diagnosed over a 2-year period based on clinical, histological and direct immunofluorescence findings. Desmoglein enzyme-linked immunosorbent assay was positive in all patients whereas indirect immunofluorescence was positive in only 25 of 29 patients. All four patients with negative indirect immunofluorescence had positive antinuclear antibodies or cytoplasmic fluorescence that could have masked the anti-intercellular antibodies. Desmoglein enzyme-linked immunosorbent assay appeared to reflect the disease activity better than indirect immunofluorescence in a few patients who had active disease of recent onset. Monkey oesophagus was found to be superior or equal to human skin as a substrate for indirect immunofluorescence in both pemphigus vulgaris and foliaceus.     

Evidence of an association between desmoglein 3 haplotypes and pemphigus vulgaris

BACKGROUND: Pemphigus vulgaris (PV, OMIM 169610) is a severe blistering disorder of the skin and mucous membranes, caused by the production of autoantibodies directed against the epithelial adhesive protein desmoglein 3. Although an association between PV and HLA class II alleles has been established, the genetic factors predisposing to the disease remain poorly understood, the rarity of PV hampering the recruitment of substantial patient cohorts. OBJECTIVES: To investigate DSG3 as a candidate PV susceptibility gene. METHODS: We examined five DSG3 single nucleotide polymorphisms (rs8085532, rs3911655, rs3848485, rs3794925 and rs1466379) in two case-control datasets respectively originating from the U.K. (62 PV patients, 154 controls) and northern India (28 patients, 98 controls). RESULTS: In the U.K. sample, we observed a significant association between PV and the DSG3*TCCTC haplotype (Fisher's exact test P = 0.002). A related haplotype (DSG3*TCCCC) was associated with PV in the Indian dataset (P = 0.002). We also found that all British and Indian patients bearing DSG3 risk haplotypes carried at least one copy of a PV-associated HLA allele. CONCLUSIONS: These results suggest that genetic variation of DSG3 may be an additive risk factor predisposing to PV and warrant further investigations of this gene.     

Neonatal pemphigus vulgaris with extensive mucocutaneous lesions from a mother with oral pemphigus vulgaris

The clinical phenotype of pemphigus is well explained by the combination of desmoglein (Dsg) 1 and Dsg3 distribution pattern and antiDsg autoantibody profile (Dsg compensation theory). It has been reported that neonatal skin has a similar Dsg distribution pattern to adult mucosal epithelia. We describe a newborn girl with mucocutaneous pemphigus vulgaris (PV) from a mother with mucosal dominant PV. The mother had had painful oral erosions for at least 7 months. Histopathological examination and direct and indirect immunofluorescence studies confirmed the diagnosis of PV and neonatal PV in the mother and daughter, respectively. The mother had a high titre of anti-Dsg3 IgG and a low titre of antiDsg1 IgG, while the neonate had only a high titre of anti-Dsg3 IgG, but no detectable antiDsg1 IgG. AntiDsg3 IgG, which caused the oral dominant phenotype in the mother, induced extensive oral as well as cutaneous lesions in the neonate. Our case provides clinical evidence for the Dsg compensation theory in neonatal PV.     

Direct immunofluorescence of the outer root sheath in anagen and telogen hair in pemphigus vulgaris and pemphigus foliaceus

Direct immunofluorescence of peri‐lesional skin is the gold standard in the diagnosis of pemphigus. A specific immunofluorescence pattern may also be demonstrated in the outer root sheath of anagen and telogen hair. We demonstrated an intercellular reticular deposition of immunoglobulin G in the outer root sheath of plucked anagen and telogen hair in all pemphigus vulgaris patients with active disease and for the first time in all patients with active pemphigus foliaceus. Moreover, we demonstrated for the first time that plucked hair samples may be kept at ?20°C for at least 2 weeks before immunofluorescent staining and analysis.     

230-kDa and 190-kDa proteins in addition to desmoglein 1 as immunological targets in a subset of pemphigus foliaceus with a combined cell-surface and basement membrane zone immune staining pattern

Pemphigus erythematosus, initially described as a combination of pemphigus with lupus erythematosus, and pemphigus foliaceus are now frequently considered localized and generalized variants of superficial pemphigus. Yet diagnostic criteria for pemphigus erythematosus remain controversial. Distinct from pemphigus foliaceus, pemphigus erythematosus displays immune depositions at the dermal-epidermal junction, which suggests additional immunopathological mechanisms. We present three patients with clinical and histopathologic signs of superficial pemphigus, who all exhibited an immunomorphology characteristic of pemphigus erythematosus. Complement depositions in a granular-linear fashion were consistently found at the dermal-epidermal junction besides in vivo bound and circulating antikeratinocyte cell-surface autoantibodies. Histopathology showed subcorneal acantholysis, and all sera contained antidesmoglein 1 but not antidesmoglein 3 autoantibodies detected by enzyme-linked immunosorbent assays (ELISA). Additional autoantibodies against a 230-kDa protein and against a 190-kDa protein comigrating with bullous pemphigoid antigen 1 (BP230) and periplakin, respectively, were present in all the patients' sera. As two sera specifically reacted with BP230 by ELISA, the presence of BP230-specific autoantibodies could be associated with dermal-epidermal immune staining in these patients. In pemphigus erythematosus, dermal-epidermal immune staining is generally attributed to the deposition of immune complexes, while the presence of BP230-specific autoantibodies has not been reported in this disease previously. Perhaps, the unique autoantibody profile of the patients in the study permits discrimination between patients with superficial pemphigus that display additional dermal-epidermal immune staining from those with conventional pemphigus foliaceus on a molecular basis. Further studies will be required to substantiate the frequency of this occurrence and to unravel its pathogenic significance.     

A study of desmoglein 1 autoantibodies in pemphigus vulgaris: racial differences in frequency and the association with a more severe phenotype

BACKGROUND: Pemphigus vulgaris (PV) is characterized by pathogenic autoantibodies to desmoglein (Dsg) 3, but additional antibodies to Dsg1, the pemphigus foliaceus antigen, are detectable in some cases. OBJECTIVES: To investigate the clinical significance of the presence of both Dsg 1 and 3 antibodies. METHODS: In 79 subjects with PV, enzyme-linked immunosorbent assays were used to detect IgG autoantibodies reactive with the ectodomain of Dsg1 and Dsg3. RESULTS: There was a clear association between the clinical phenotype and the Dsg antibody profile. All subjects had Dsg3 autoantibodies and 61% had coexisting Dsg1 antibodies (Dsg3+/Dsg1+). PV limited entirely to the mucosal surfaces was seen only in Dsg3+/Dsg1- patients, while additional Dsg1 antibodies (Dsg3+/Dsg1+) predicted cutaneous in addition to mucosal involvement. Although minor cutaneous involvement was observed in most Dsg3+/Dsg1- patients, severe cutaneous involvement was seen only in Dsg3+/Dsg1+ patients. Dsg1 antibodies were detectable early in the course of disease and their appearance did not relate to the use of systemic therapy. The proportion of Dsg1+ patients was higher in those of Indian origin compared with white northern Europeans (P < 0.05). CONCLUSIONS: These data suggest that the presence of Dsg1 antibodies is predictive of a potentially more severe disease and that genetic factors may determine the Dsg antibody profile.     

Usefulness of enzyme-linked immunosorbent assay using recombinant desmogleins 1 and 3 for serodiagnosis of pemphigus

Pemphigus is an autoimmune blistering disease with two major subtypes, pemphigus vulgaris (PV) and pemphigus foliaceus (PF). Patients with pemphigus have circulating antidesmoglein (Dsg)1 and/or anti-Dsg3 IgG autoantibodies. We have previously developed enzyme-linked immunosorbent assays (ELISAs) using recombinant Dsg1 and Dsg3 expressed by baculovirus as a diagnostic tool for pemphigus. The purpose of this study was to evaluate the practical application of these ELISAs for clinical use with a large number of serum samples. We used 81 PV sera, 48 PF sera, 114 bullous pemphigoid (BP) sera, 124 collagen disease sera, nine sera of other non-pemphigus bullous diseases and 179 normal control sera. A cut-off value was determined by receiver-operating-characteristic plots. Forty-seven of 48 PF sera (97.9%) were positive in the Dsg1 ELISA and 79 of 81 PV sera (97.5%) were positive in the Dsg3 ELISA, while only two (1. 1%) and four (2.2%) of 179 normal sera were positive in Dsg1 and Dsg3 ELISAs, respectively. However, some disease control sera of BP and collagen diseases exceeded the cut-off value. Introduction of a grey zone helped to decrease the number of these false-positive sera. Furthermore, in three patients studied, the respective Dsg1 and Dsg3 ELISA scores showed parallel fluctuation with the disease activity along the time course. We conclude that Dsg1 and Dsg3 ELISAs provide a simple, sensitive and highly specific assay for the diagnosis of patients with PV and PF and that these ELISAs may be a valuable tool to monitor the disease activity. We also propose diagnostic criteria for pemphigus based on ELISA reactivity: if a serum is positive against Dsg3 it indicates a diagnosis of PV, regardless of reactivity against Dsg1; if a serum is negative for Dsg3 and positive for Dsg1, it indicates a diagnosis of PF.     

Transgenic rescue of desmoglein 3 null mice with desmoglein 1 to develop a syngeneic mouse model for pemphigus vulgaris

Background

An active disease mouse model of pemphigus vulgaris (PV) was developed using the adoptive transfer of splenocytes from Dsg3^−/− mice with a mixed C57BL/6J (B6) and 129/Sv genetic background into B6-Rag2^−/− mice. Further immunological investigation is needed to resolve the genetic mismatch between host and recipient mice. The B6-Dsg3^−/− mice did not grow old enough to provide splenocytes, probably due to severe oral erosions, with resulting inhibition of food intake.

Objective

To rescue the B6-Dsg3^−/− mice and to produce syngeneic PV model mice.

Methods

Transgenic expression of mouse Dsg1 was attempted to compensate for the genetic loss of Dsg3 using the keratin 5 promoter. We evaluated the compensatory ability of Dsg1 in vivo by comparing Dsg1^wt/wt, Dsg1^tg/wt, and Dsg1^tg/tg mice. We generated a PV model via the adoptive transfer of B6-Dsg1^tg/tgDsg3^−/− splenocytes to B6-Rag2^−/− mice.

Results

Dsg1^tg/tg and Dsg1^tg/wt mice expressed ectopic Dsg1 on keratinocyte cell surfaces in the lower layers of the epidermis, oral epithelium, and telogen hair follicles. Ectopic Dsg1 blocked the pathogenic effects of AK23 anti-Dsg3 mAb, and improved the body weight loss, telogen hair loss, and survival rate dose-dependently. While the B6-Dsg1^wt/wtDsg3^−/− mice died by week 2, over 80% of the B6-Dsg1^tg/tgDsg3^−/− mice survived at week 6. Furthermore, the syngeneic PV model mice showed the characteristic phenotype, including stable anti-Dsg3 antibody production and suprabasilar acantholysis on histology.

Conclusion

Transgenic expression of Dsg1 rescued the severe B6-Dsg3^−/− phenotype and provided a syngeneic mouse model of PV, which may be a valuable tool for clarifying immunological mechanisms in autoimmunity and tolerance of Dsg3.     

Coexistence of IgA antibodies to desmogleins 1 and 3 in pemphigus vulgaris, pemphigus foliaceus and paraneoplastic pemphigus

BACKGROUND: Pemphigus is a bullous mucocutaneous autoimmune disease characterized by IgG autoantibodies to desmoglein (Dsg) 1 and/or Dsg3. Occasionally direct immunofluorescence of pemphigus skin reveals IgA depositions with an intraepidermal intercellular pattern in addition to the IgG deposition. OBJECTIVES: To investigate if pemphigus patients, in addition to having IgG autoantibodies, also generate IgA antibodies to Dsg1 and/or Dsg3. PATIENTS/METHODS: Sera of 100 pemphigus patients and 36 bullous pemphigoid controls were tested by IgA enzyme-linked immunosorbent assay (ELISA) to the recombinant extracellular domains of Dsg1 and Dsg3. The patients were selected on clinical grounds and positive IgG ELISA index values for Dsg1 and/or Dsg3. They were divided into four groups: patients having IgG to only Dsg1 (n=34), patients having IgG to both Dsg1 and Dsg3 (n=31), patients having IgG to only Dsg3 (n=27) and patients who had paraneoplastic pemphigus (PNP) (n=8). RESULTS: IgA antibodies to Dsg1 were found in 13 (38%) of the patients with IgG to Dsg1, in five (16%) of the patients with IgG to both Dsg1 and Dsg3, in four (15%) of the patients with IgG to Dsg3 and in none of the PNP patients. IgA antibodies to Dsg3 were found in one (3%) of the patients with IgG to Dsg1, in 18 (58%) of the patients with IgG to both Dsg1 and 3, in 18 (67%) of the patients with IgG to Dsg3, and in four (50%) of the PNP patients. Immunofluorescence analysis demonstrated intraepidermal intercellular staining IgA antibodies in serum and intercellular IgA deposits in skin of IgA ELISA-positive patients, although to a lesser extent than by ELISA. CONCLUSIONS: This study shows that in a considerable number of supposedly IgG-mediated pemphigus patients IgA to Dsg1 and Dsg3 is also present. In most cases the antigen specificity of the IgA follows the antigen specificity of the IgG, although in a small number of cases IgA is present against the Dsg not recognized by IgG.     

The treatment of mild pemphigus vulgaris and pemphigus foliaceus with a topical corticosteroid

Seven patients with mild pemphigus vulgaris (n = 3) or pemphigus foliaceus (n = 4) were treated with a very potent topical corticosteroid alone. Clobetasol propionate 0.05% cream was applied to mucosal lesions and involved skin twice a day for at least 15 days, then progressively tapered. Pemphigus was considered to be controlled if healing of lesions was obtained, with a 75% decrease in the number of new lesions per week without addition of any systemic treatment. In all seven patients, the disease was controlled initially with healing of cutaneous lesions within 15 days, while healing of mucosal lesions took at least 1 month. In four patients, remission was maintained with topical corticosteroid alone for a mean 19-month follow-up. In three patients, relapse occurred after 2-11 months, requiring a systemic treatment.     

The humanized SCID mouse model to study HLA class II-linked autoimmunity to desmoglein 3 in pemphigus vulgaris

BACKGROUND: Pemphigus vulgaris (PV) is a severe autoimmmune skin disorder induced by antibodies against desmoglein (Dsg) 3 on epidermal keratinocytes. OBJECTIVES: To establish an active animal model of PV to analyse the T-cell-regulated production of pathogenic antibodies in vivo. METHODS: Immunodeficient SCID mice were injected with peripheral blood lymphocytes (PBL) from an HLA-DRB1*0402/DQ8+ patient with PV or a DRB1*0402/DQ8+ healthy donor, with or without subsequent injections of human Dsg3 or preincubation of PBL with Dsg3. RESULTS: Human immunoglobulins (2.7-18.5 mg mL-1) were detected in all the mice after 8 weeks. Only one of 30 PBL-treated mice developed IgM against Dsg3 and showed intercellular IgM deposits in skin, nostrils and tongue. In contrast, in a previous study, 41% of SCID mice injected with PBL from patients with PV developed anti-Dsg3 antibodies in vivo. CONCLUSIONS: Our inability to reproduce these findings may be due to the transfer of slightly lower numbers of PBL (20 x 10(6) vs. 25-30 x 10(6)).     

Monopathogenic vs multipathogenic explanations of pemphigus pathophysiology

This viewpoint highlights major, partly controversial concepts about the pathogenesis of pemphigus. The monopathogenic theory explains intra‐epidermal blistering through the “desmoglein (Dsg) compensation” hypothesis, according to which an antibody‐dependent disabling of Dsg 1‐ and/or Dsg 3‐mediated cell–cell attachments of keratinocytes (KCs) is sufficient to disrupt epidermal integrity and cause blistering. The multipathogenic theory explains intra‐epidermal blistering through the “multiple hit” hypothesis stating that a simultaneous and synchronized inactivation of the physiological mechanisms regulating and/or mediating intercellular adhesion of KCs is necessary to disrupt epidermal integrity. The major premise for a multipathogenic theory is that a single type of autoantibody induces only reversible changes, so that affected KCs can recover due to a self‐repair. The damage, however, becomes irreversible when the salvage pathway and/or other cell functions are altered by a partnering autoantibody and/or other pathogenic factors. Future studies are needed to (i) corroborate these findings, (ii) characterize in detail patient populations with non‐Dsg‐specific autoantibodies, and (iii) determine the extent of the contribution of non‐Dsg antibodies in disease pathophysiology.     

Low pathogenicity of anti‐desmoglein 3 immunoglobulin G autoantibodies contributes to the atypical clinical phenotypes in pemphigus

The clinical phenotypes of pemphigus can be explained by the desmoglein (Dsg) compensation theory. However, some atypical cases such as cutaneous pemphigus vulgaris (cPV), in which patients have anti‐Dsg3 antibodies without oral erosions, do not conform to this theory. To explain the discrepancy between clinical phenotypes and anti‐Dsg antibody profiles, the pathogenic strength of immunoglobulin (Ig)G autoantibodies against Dsg3 must be taken into consideration. We analyzed the epitopes and blister‐inducing pathogenic strength of the sera from three patients having IgG against Dsg3 without oral erosions with domain‐swapped recombinant proteins and dissociation assay using cultured normal human epidermal keratinocytes. The results showed that all sera contained IgG directed against the amino terminal EC1 domain of Dsg3, as is found in most PV sera. However, dissociation assays revealed that the pathogenic strength of the anti‐Dsg3 antibodies in all three cases was extremely lower than that of typical PV cases with mucosal involvement. In conclusion, when anti‐Dsg3 IgG antibodies are not sufficient to inhibit the expression of Dsg3 in the oral mucosa, but can inhibit the expression in the skin, skin blisters can result. Therefore, the pathogenicity of anti‐Dsg3 antibodies should be regarded as a key factor contributing to the clinical phenotype in pemphigus patients with conflicting antibody profiles.