Unusual pemphigus phenotype in the presence of a Dsg1 and Dsg3 autoantibody profile

Case report: Documentation of cutaneous only pemphigus vulgaris without history of mucosal lesions in North America

Background

Pemphigus is a group of autoimmune blistering diseases including Pemphigus vulgaris (PV) and Pemphigus foliaceus (PF). These conditions exhibit lesions with mucosal or mucocutaneous (PV) or cutaneous (PF) morphology, as framed by the Desmoglein Compensation Hypothesis (DCH). However, some PV patients present with solely cutaneous disease (cPV), and growing evidence suggests the existence of a cPV subtype without any history of mucosal erosions/blisters (cPVwohm), neither of which are predicted by the DCH.

Methods

Participants were recruited from several outpatient clinical settings and patient support group meetings throughout the US. On intake, subjects provided blood samples and completed questionnaires regarding their disease status.

Results

We report three cases of clinically and histologically confirmed cPV without history of mucosal lesions (cPVwohm). Of these patients, two do not carry the most common PV associated HLA alleles, DRB1*0402 or DQB1*0503. The same two patients also tested negative for the primary PV associated autoantibodies, anti-desmoglein 3 and anti-desmoglein 1, while in active disease status.

Conclusion

We confirm the first documented individual cases of cPVwohm in North America, supporting the existence of PV patients that develop cutaneous disease without a history of mucosal lesions, challenging the fidelity of the DCH. Two of the 3 patients reported did not type for the common PV-associated HLA genes or display anti-desmoglein autoantibodies while in active disease, suggesting cPV patients may develop Pemphigus via genetic and immune mechanisms that differ from typical mucosal or mucocutaneous PV.

Disease progression and response to therapy in pemphigus based on a registry

BACKGROUND AND OBJECTIVES

Pemphigus diseases are potentially life-threatening and rare autoimmune bullous disorders characterized by blisters and erosions of the skin and mucous membranes. These disorders can be largely divided into two major subtypes: pemphigus vulgaris (PV) and pemphigus foliaceus (PF). The objective of this study was to evaluate the autoantibody profile and response to therapy of PV and PF patients by analyzing the clinicopathological data from a registry for bullous autoimmune dermatoses.

PATIENTS AND METHODS

In a retrospective study, data from 69 patients with PV and PF were included in the analysis. The Autoimmune Bullous Skin Intensity Score (ABSIS) was used to assess the clinical course, remissions, relapses and severity of the disease at first manifestation and throughout the observation period. ELISA was performed to assess levels of anti-desmoglein (Dsg)-1 and anti-Dsg3 IgG serum autoantibodies.

RESULTS

The mean remission time in PV and PF patients was 63 weeks. PV patients with mucosal involvement showed a more favorable healing process. In PV patients with a moderate/high anti-Dsg1 IgG serum level at baseline, anti-Dsg3 IgG levels decreased during the observation period.

CONCLUSIONS

Our study provides additional insights into the clinical course of patients with PV and PF, revealing that a mucosal phenotype is associated with a higher tendency towards remission.

Register-Studie zu Krankheitsentwicklung und Therapieansprechen bei Pemphigus

HINTERGRUND UND ZIELE

Pemphigus gehört zu den seltenen, aber potentiell lebensbedrohlichen Autoimmunerkrankungen. Typisch sind Blasen und Erosionen der Haut und der Schleimhäute. Grundsätzlich unterscheiden wir zwei Subtypen: Pemphigus vulgaris (PV) und Pemphigus foliaceus (PF). In dieser Studie wurden die klinisch-pathologischen Daten aus einem Register für bullöse Autoimmundermatosen analysiert mit dem Ziel, das Autoantikörperprofil und das Therapieansprechen bei Patienten mit PV und PF genauer zu charakterisieren.

PATIENTEN UND METHODEN

In einer retrospektiven Studie wurden die Daten von 69 Patienten mit PV und PF analysiert. Zur Beurteilung des klinischen Verlaufs, der Remissionen und Rezidive sowie des Schweregrads der Krankheit bei Erstmanifestation und während des gesamten Beobachtungszeitraums diente der ABSIS (Autoimmune Bullous Skin Intensity Score) (ABSIS). Mittels ELISA wurden die Spiegel von Anti-Desmoglein (Dsg)-1- und Anti-Dsg- IgG-Autoantikörpern im Serum bestimmt.

ERGEBNISSE

Die mittlere Remissionszeit bei Patienten mit PV und PF betrug 63 Wochen. PV-Patienten mit Schleimhautbeteiligung zeigten eine schnellere Heilung. Bei PV-Patienten mit moderat oder stark erhöhten Anti-Dsg1-IgG-Autoantikörpern im Serum zu Beginn erfolgte im Lauf des Beobachtungszeitraums ein Absinken der Anti-Dsg3-IgG-Spiegel.

SCHLUSSFOLGERUNGEN

Unsere Studie liefert neue Erkenntnisse zum Krankheitsverlauf bei Patienten mit PV und PF und offenbart, dass ein Phänotyp mit Schleimhautbeteiligung eine stärkere Neigung zur Remission aufweist.

The Evolving Story of Autoantibodies in Pemphigus Vulgaris: Development of the "Super Compensation Hypothesis"

Emerging data and innovative technologies are re-shaping our understanding of the scope and specificity of the autoimmune response in Pemphigus vulgaris (PV), a prototypical humorally mediated autoimmune skin blistering disorder. Seminal studies identified the desmosomal proteins Desmoglein 3 and 1 (Dsg3 and Dsg1), cadherin family proteins which function to maintain cell adhesion, as the primary targets of pathogenic autoAbs. Consequently, pathogenesis in PV has primarily considered to be the result of anti-Dsg autoAbs alone. However, accumulating data suggesting that anti-Dsg autoAbs by themselves cannot adequately explain the loss of cell-cell adhesion seen in PV, nor account for the disease heterogeneity exhibited across PV patients has spurred the notion that additional autoAb specificities may contribute to disease. To investigate the role of non-Dsg autoAbs in PV, an increasing number of studies have attempted to characterize additional targets of PV autoAbs. The recent advent of protein microarray technology, which allows for the rapid, highly sensitive, and multiplexed assessment of autoAb specificity has facilitated the comprehensive classification of the scope and specificity of the autoAb response in PV. Such detailed deconstruction of the autoimmune response in PV, beyond simply tracking anti-Dsg autoAbs, has provided invaluable new insights concerning disease mechanisms and enhanced disease classification which could directly translate into superior tools for prognostics and clinical management, as well as the development of novel, disease specific treatments.

Urban legends: pemphigus vulgaris

Pemphigus vulgaris (PV) is the most common type of pemphigus. PV pathogenesis is still debated, and treatment remains challenging. We investigated five controversial topics: (1) What are the target antigens in PV? (2) Do desmogleins adequately address PV pathophysiology? (3) How does acantholysis occur in PV? (4) Is PV still a lethal disease? (5) What is the role of rituximab (RTX) in PV treatment? Results from extensive literature searches suggested the following: (1) Target antigens of PV include a variety of molecules and receptors that are not physically compartmentalized within the epidermis. (2) PV is caused by a variety of autoantibodies to keratinocyte self-antigens, which concur to cause blistering by acting synergistically. (3) The concept of apoptolysis distinguishes the unique mechanism of autoantibody-induced keratinocyte damage in PV from other known forms of cell death. (4) PV remains potentially life-threatening largely because of treatment side effects, but it is uncertain which therapies carry the highest likelihood of lethal risk. (5) RTX is a very promising treatment option in patients with widespread recalcitrant or life-threatening PV. RTX's cost is an issue, its long-term side effects are still unknown, and randomized controlled trials are needed to establish the optimal dosing regimen.

Pemphigus herpetiformis: analysis of the autoantibody profile during the disease course with changes in the clinical phenotype

BACKGROUND

Pemphigus herpetiformis (PH) is a rare dapsone-responsive variant of pemphigus, characterized by annular and vesiculopustular cutaneous lesions. Most PH serum samples contain autoantibodies against desmoglein (Dsg)1, but not Dsg3, and the presence of the latter is almost invariably associated with mucosal involvement, as predicted based on the 'Dsg compensation theory'.

METHODS

We describe a patient with features characteristic of PH with histologically eosinophilic spongiosis who repeatedly tested positive for anti-Dsg3 but not anti-Dsg1 autoantibodies by ELISA. To investigate whether the peculiar clinical phenotype was due to a distinct immunological profile, the patient's serum was tested by ELISA and immunoblotting using recombinant forms of Dsg3.

RESULTS

Serum samples were found to have low and high reactivity against the EC1 and the EC4 domains of Dsg3, respectively, whereas the autoantibodies belonged predominantly to the IgG1 and IgG4 subclasses. The overall immunological profile was typical of pemphigus vulgaris. The patient finally developed isolated oral erosions 22 months after initial presentation, without significant changes in the autoantibody profile and of the targeted antigenic sites.

CONCLUSIONS

Our patient presented features characteristic of PH. Although circulating anti-Dsg3 antibodies were present, the patient had only cutaneous involvement for a long period. Our findings indicate that the proposed Dsg compensation theory cannot always explain the clinical phenotype, changes in which may occur without apparent modification of the autoantibody profile and antibody specificity. Hence, additional factors, such as Fcgamma-dependent neutrophil activation, may critically affect the clinical presentation of pemphigus.

The desmosome and pemphigus

Desmosomes are patch-like intercellular adhering junctions ("maculae adherentes"), which, in concert with the related adherens junctions, provide the mechanical strength to intercellular adhesion. Therefore, it is not surprising that desmosomes are abundant in tissues subjected to significant mechanical stress such as stratified epithelia and myocardium. Desmosomal adhesion is based on the Ca(2+)-dependent, homo- and heterophilic transinteraction of cadherin-type adhesion molecules. Desmosomal cadherins are anchored to the intermediate filament cytoskeleton by adaptor proteins of the armadillo and plakin families. Desmosomes are dynamic structures subjected to regulation and are therefore targets of signalling pathways, which control their molecular composition and adhesive properties. Moreover, evidence is emerging that desmosomal components themselves take part in outside-in signalling under physiologic and pathologic conditions. Disturbed desmosomal adhesion contributes to the pathogenesis of a number of diseases such as pemphigus, which is caused by autoantibodies against desmosomal cadherins. Beside pemphigus, desmosome-associated diseases are caused by other mechanisms such as genetic defects or bacterial toxins. Because most of these diseases affect the skin, desmosomes are interesting not only for cell biologists who are inspired by their complex structure and molecular composition, but also for clinical physicians who are confronted with patients suffering from severe blistering skin diseases such as pemphigus. To develop disease-specific therapeutic approaches, more insights into the molecular composition and regulation of desmosomes are required.

Pemphigus IgG causes skin splitting in the presence of both desmoglein 1 and desmoglein 3

According to the desmoglein (Dsg) compensation concept, different epidermal cleavage planes observed in pemphigus vulgaris and pemphigus foliaceus have been proposed to be caused by different autoantibody profiles against the desmosomal proteins Dsg 1 and Dsg 3. According to this model, Dsg 1 autoantibodies would only lead to epidermal splitting in those epidermal layers in which no Dsg 3 is present to compensate for the functional loss of Dsg 1. We provide evidence that both pemphigus foliaceus-IgG containing Dsg 1- but not Dsg 3-specific antibodies and pemphigus vulgaris-IgG with antibodies to Dsg 1 and Dsg 3 were equally effective in causing epidermal splitting in human skin and keratinocyte dissociation in vitro. These effects were present where keratinocytes expressed both Dsg 1 and Dsg 3, demonstrating that Dsg 3 does not compensate for Dsg 1 inactivation. Rather, the cleavage plane in intact human skin caused by pemphigus autoantibodies was similar to the plane of keratinocyte dissociation in response to toxin B-mediated inactivation of Rho GTPases. Because we recently demonstrated that pemphigus-IgG causes epidermal splitting by inhibition of Rho A, we propose that Rho GTPase inactivation contributes to the mechanisms accounting for the cleavage plane in pemphigus skin splitting.

Plakoglobin-dependent disruption of the desmosomal plaque in pemphigus vulgaris

We recently reported that the pathogenesis of pemphigus vulgaris (PV), an autoimmune blistering skin disorder, is driven by the accumulation of c-Myc secondary to abrogation of plakoglobin (PG)-mediated transcriptional c-Myc suppression. PG knock-out mouse keratinocytes express high levels of c-Myc and resemble PVIgG-treated wild-type keratinocytes in most respects. However, they fail to accumulate nuclear c-Myc and loose intercellular adhesion in response to PVIgG-treatment like wild-type keratinocytes. This suggested that PG is also required for propagation of the PVIgG-induced events between augmented c-Myc expression and acantholysis. Here, we addressed this possibility by comparing PVIgG-induced changes in the desmosomal organization between wild-type and PG knock-out keratinocytes. We found that either bivalent PVIgG or monovalent PV-Fab (known to trigger blister formation in vivo) disrupt the linear organization of all major desmosomal components along cell borders in wild-type keratinocytes, simultaneously with a reduction in intercellular adhesive strength. In contrast, PV-Fab failed to affect PG knock-out keratinocytes while PVIgG cross-linked their desmosomal cadherins without significantly affecting desmoplakin. These results identify PG as a principle effector of the PVIgG-induced signals downstream of c-Myc that disrupt the desmosomal plaque at the plasma membrane.

Upregulation of c-Myc may contribute to the pathogenesis of canine pemphigus vulgaris

The pathomechanism in human pemphigus vulgaris (PV) has recently been described to rely on generalized c-Myc upregulation in skin and oral mucosa followed by hyperproliferation. Here we assessed whether dogs suffering from PV present the same pathological changes as described for human patients with PV. Using immunofluorescence analysis on patients' biopsy samples, we observed marked nuclear c-Myc accumulation in all layers of the epidermis and oral mucosa in all (3/3) dogs analysed. In addition, c-Myc upregulation was accompanied by an increased number of proliferating Ki67-positive cells. These molecular changes were further paralleled by deregulated expression of wound healing and terminal differentiation markers as observed in human PV. Together these findings suggest a common pathomechanism for both species which is of particular relevance in the light of the recently discussed novel therapeutic strategies aiming at targeting PV antibody-induced signalling cascades.

How does acantholysis occur in pemphigus vulgaris: a critical review

BACKGROUND

Pemphigus vulgaris is a life-threatening autoimmune blistering disease targeting skin and mucous membranes, characterized by disruption of keratinocytes' adhesion termed acantholysis. Today multiple classes of targets are considered to play a role in the genesis of the acantholysis; of these, the classical pemphigus antigens, desmosomal cadherins (desmoglein 1 and 3) are the best characterized and considered as the most important. Additional antigens include the novel epithelial acetylcholine receptors (alpha9 and pemphaxin). Thus, acantholysis in pemphigus seems to result from a cooperative action of antibodies to different keratinocyte self-antigens, but the mechanisms by which epithelial cleft occurs are not yet clearly understood. In fact, the binding of the autoantibodies to these targets generates a plethora of biological effects due, on one hand, to their direct interference with adhesive function and, on the other, to more complex events involving intracellular pathways that modify proteases activity or calcium metabolism, leading to loss of cell-cell adhesion.

Cutaneous type pemphigus vulgaris: a rare clinical phenotype of pemphigus

Pemphigus is an autoimmune blistering disease of the skin, mucous membranes, or both. There are two main categories of pemphigus: pemphigus foliaceus (PF) and pemphigus vulgaris (PV). PV is further subdivided into mucosal dominant and mucocutaneous types, according to the extent of cutaneous lesions. These classes of pemphigus have distinct histopathologic and serologic findings, with most cases falling into these subtypes. We report 4 cases that clinically showed blisters and erosions in the skin only, without mucosal involvement. Histologic examination of cutaneous lesions demonstrated suprabasilar acantholysis, a typical finding for PV. These patients had predominant anti-desmoglein 1 (Dsg1) IgG autoantibodies as well as anti-Dsg3 IgG autoantibodies, as determined by enzyme-linked immunosorbent assay. The desmoglein compensation theory posits that this rare phenotype can be produced by pathogenically weak anti-Dsg3 IgG in the presence of potent anti-Dsg1 IgG autoantibodies. Thus, cutaneous type PV without apparent mucosal involvement is observed as a rare clinical and histologic expression of pemphigus. This expression can be a transient phenotype that may develop from, or evolve into, other subtypes of pemphigus.