Bullous Autoimmune Dermatoses

Advancements in Bullous Pemphigoid Treatment: A Comprehensive Pipeline Update

ABASTRACT

Bullous pemphigoid (BP) is a common autoimmune bullous disease affecting mainly the elderly, with rising incidence due to increased life expectancy. This disease is characterized by tense bullous lesions on normal or erythematous skin, accompanied by pruritus. BP pathogenesis involves autoantibodies against hemidesmosomal proteins BP180 and BP230, leading to detachment at the dermo-epidermal junction as well as blister formation. BP is associated with coexisting comorbidities and drug exposure, and its management often requires high doses or chronic use of systemic glucocorticoids, posing risks of adverse effects. This review focuses on novel treatment options for BP, exploring therapies targeting different immune pathways. Rituximab, a CD20 monoclonal antibody, depletes B-lymphocytes and has shown efficacy in severe cases. Dupilumab, targeting interleukin (IL)-4 receptor α and thus blocking IL-4 and IL-13, downregulates type 2 helper (Th2) responses and has demonstrated promising results. Targeting eosinophil-related molecules using bertilimumab and AKST4290 has yielded positive results in clinical trials. Omalizumab, an immunoglobulin (Ig) E antibody, can reduce disease severity and allows corticosteroid tapering in a number of cases. Complement inhibitors such as nomacopan and avdoralimab are being investigated. IL-17 and IL-23 inhibitors such as secukinumab and tildrakizumab have shown potential in a limited number of case reports. Neonatal Fc receptor antagonists such as efgartigimod are under investigation. Additionally, topical therapies and Janus kinase inhibitors are being explored as potential treatments for BP. These novel therapies offer promising alternatives for managing BP, with potential to improve outcomes and reduce high cumulative doses of systemic corticosteroids and related toxicities. Further research, including controlled clinical trials, is needed to establish their efficacy, safety, and optimal dosing regimens for BP management.

Autoimmunity against laminin 332

Laminin 332 is a heterotrimeric structural protein of the basal membrane zone (BMZ) of the skin and adjacent mucosal tissues. The importance of laminin 332 for the structural integrity of the BMZ is demonstrated by mutations in any of the three genes encoding for its three chains causing variants of junctional epidermolysis bullosa. Autoimmunity against laminin 332 is observed in mucous membrane pemphigoid (MMP) and in the rare patients with orf-induced pemphigoid. MMP is an autoimmune blistering disease with predominant mucosal manifestations and autoantibodies against the BMZ of the skin and orifice-close mucous membranes. The main autoantigens of MMP are type XVII collagen (BP180) and laminin 332 targeted in about 80% and 10-20% of patients, respectively. An increasing number of studies has highlighted the association of anti-laminin 332 MMP and malignancies that can be revealed in about a quarter of these patients. This data has led to the recommendation of current guidelines to assay for anti-laminin 332 reactivity in all MMP patients. The present review focuses on anti-laminin 332 MMP describing clinical features, its pathophysiology, and detection of serum anti-laminin 332 IgG. In addition, the available data about the occurrence of malignancies in anti-laminin 332 MMP, the underlying tumor entities, and its biology are detailed.

Autoimmune blistering diseases: promising agents in clinical trials

INTRODUCTION

Treatment options for autoimmune bullous diseases (AIBD) are currently limited to corticosteroids and traditional immunomodulants and immunosuppressants that are associated with unfavorable adverse effect profiles. The most frequent AIBDs, i.e. bullous pemphigoid, pemphigus vulgaris, and mucous membrane pemphigoid, impose a high disease burden onto affected patients and can be detrimental due to infections, exsiccosis, and impaired food intake. Significant progress has been made in elucidating disease mechanisms and key mediators by in vivo and in vitro models, thus identifying a multifaceted range of possible drug targets. However, except for rituximab for pemphigus vulgaris, no new drugs have been approved for the treatment of AIBDs in the last decades.

AREAS COVERED

This review covers new drug developments and includes ongoing or completed phase 2 and 3 clinical trials. Studies were identified by querying the registries of ClinicalTrials.gov and Cochrane Library.

EXPERT OPINION

Promising results were shown for a variety of new agents including nomacopan, efgartigimod, omalizumab, dupilumab, as well as chimeric autoantibody receptor T cells. Clinical translation in the field of AIBDs is highly active, and we anticipate significant advances in the treatment landscape.

Comorbidity in bullous pemphigoid: up-date and clinical implications

Bullous pemphigoid is the most common autoimmune blistering disease in industrialized countries and particularly affects the elderly. In this patient population, comorbid diseases are frequent and may complicate management and treatment of bullous pemphigoid. A better understanding why distinct diseases are more frequent in bullous pemphigoid patients may lead to new pathophysiological insights and - as a consequence - result in better patient care. The association of bullous pemphigoid with neurological and psychiatric diseases is well known and confirmed by several case-control studies. Association with further diseases such as malignancy and metabolic diseases are still discussed controversially. In recent years new relationships between bullous pemphigoid and autoimmune as well as inflammatory skin diseases have been reported. This review provides a systematic overview on studies addressing comorbidity in bullous pemphigoid patients. Increasing the awareness of both, common and rare comorbid diseases, may enable clinicians to optimize patient support and individualized treatment of bullous pemphigoid.

[Diagnostics of ocular mucous membrane pemphigoid]

The diagnosis of ocular mucous membrane pemphigoid (MMP) remains a challenge as the timing and choice of diagnostic methods have a decisive influence on its quality. A systematic approach is required that includes a comprehensive medical history, critical evaluation of the clinical findings and targeted laboratory testing. The diagnosis is complicated by the fact that some patients present purely clinically the symptoms of MMP without fulfilling the required immunohistochemical and laboratory criteria. Basically, the diagnosis of ocular MMP is based on three pillars: 1) medical history and clinical findings, 2) positive immunohistological (direct immunofluorescence) tissue sample and 3) specific serological autoantibodies. As the diagnosis of ocular MMP often implies prolonged systemic immunomodulatory treatment in predominantly older patients, the accurate diagnosis and approach are of critical relevance. The aim of this article is to present the recently updated diagnostic procedure.

[Clinical aspects of ocular mucosal pemphigoid]

Mucosal pemphigoid is a rare chronic autoimmune disease that also affects the eyes in more than two thirds of all cases. Especially in the early phase of the ocular manifestation, the findings are subtle and the disease is often not recognized. The aim of this article is to provide the clinical aspects of ocular mucosal pemphigoid so that timely diagnostics can be initiated when this disease is suspected.

Mouse models of pemphigus: valuable tools to investigate pathomechanisms and novel therapeutic interventions

Autoimmune blistering diseases (AIBD) are paradigms of autoantibody-mediated organ-specific autoimmune disorders that involve skin and/or mucous membranes. Compared to other autoimmune diseases, the pathogenicity of autoantibodies in AIBD is relatively well described. Pemphigus is a potentially lethal autoantibody driven autoimmune disorder with a strong HLA class II association. It is mainly characterized by IgG against the desmosomal adhesion molecules desmoglein 3 (Dsg3) and Dsg1. Several murine pemphigus models were developed subsequently, each allowing the analysis of a characteristic feature, such as pathogenic IgG or Dsg3-specific T or B cells. Thus, the models can be employed to preclinically evaluate potentially novel therapies. We here thoroughly summarize past and recent efforts in developing and utilizing pemphigus mouse models for pathomechanistic investigation and therapeutic interventions.

Direct Immunofluorescence of IgG on Formalin-Fixed Paraffin-Embedded Tissue by Heat-Induced Antigen Retrieval as a Sensitive Method for the Diagnosis of Pemphigus

Purpose

Direct immunofluorescence (DIF) on frozen sections (DIF-F) plays a key role in the identification and differential diagnosis of bullous dermatoses, which are a group of critical autoimmune diseases that include pemphigus, bullous pemphigoid (BP), and epidermolysis bullosa acquisita (EBA). However, this technique requires specialized laboratory equipment conditions, sample acquisition and sample preservation. In this study, the application value of DIF on paraffin-embedded tissue sections (DIF-P) detecting IgG using heat-induced antigen retrieval (HIAR) in the diagnosis of bullous dermatosis was explored.

Patients and Methods

Samples from 12 patients with pemphigus vulgaris (PV), 10 patients with pemphigus foliaceus (PF), 17 patients with BP, and 4 patients with EBA were retrospectively studied for DIF-P IgG detection. Formalin-fixed, paraffin-embedded tissue (FFPE) was used, and the antigen retrieval method used in the experiment was HIAR. All patients were diagnosed with the autoimmune bullous disease (AIBD) based on clinical presentation, histopathology, DIF-F, and enzyme-linked immunosorbent assay (ELISA).

Results

Intercellular staining for IgG in the epidermis was successful in paraffin-embedded tissue sections in 11 of 12 PV samples and in all 10 PF samples. IgG at the basement membrane zone (BMZ) was not detected by immunofluorescent staining in 17 BP samples and 4 EBA samples.

Conclusion

The detection of IgG by DIF-P using HIAR can be used for the diagnosis of pemphigus as an alternative method to DIF-F.

Computer-aided classification of indirect immunofluorescence patterns on esophagus and split skin for the detection of autoimmune dermatoses

Autoimmune bullous dermatoses (AIBD) are rare diseases that affect human skin and mucous membranes. Clinically, they are characterized by blister formation and/or erosions. Depending on the structures involved and the depth of blister formation, they are grouped into pemphigus diseases, pemphigoid diseases, and dermatitis herpetiformis. Classification of AIBD into their sub-entities is crucial to guide treatment decisions. One of the most sensitive screening methods for initial differentiation of AIBD is the indirect immunofluorescence (IIF) microscopy on tissue sections of monkey esophagus and primate salt-split skin, which are used to detect disease-specific autoantibodies. Interpretation of IIF patterns requires a detailed examination of the image by trained professionals automating this process is a challenging task with these highly complex tissue substrates, but offers the great advantage of an objective result. Here, we present computer-aided classification of esophagus and salt-split skin IIF images. We show how deep networks can be adapted to the specifics and challenges of IIF image analysis by incorporating segmentation of relevant regions into the prediction process, and demonstrate their high accuracy. Using this semi-automatic extension can reduce the workload of professionals when reading tissue sections in IIF testing. Furthermore, these results on highly complex tissue sections show that further integration of semi-automated workflows into the daily workflow of diagnostic laboratories is promising.

[Trigger factors associated with bullous autoimmune dermatoses]

BACKGROUND

Blistering autoimmune dermatoses are a heterogeneous group of rare diseases. Pemphigus diseases are distinguished from pemphigoid diseases as well as dermatitis herpetiformis. In pemphigus diseases, cutaneous blistering is caused by an intraepidermal loss of adhesion between keratinocytes. In pemphigoid diseases, blister formation is due to a subepidermal loss of adhesion of keratinocytes from the basement membrane.

OBJECTIVES

This article reviews the most important trigger factors associated with bullous autoimmune dermatoses and discusses their role in their initial manifestation as well as exacerbation.

MATERIALS AND METHODS

A focused review of the literature including original articles, guidelines, reference works and previously published review articles was performed.

RESULTS

Vaccinations, viral infections, ultraviolet light (UV) exposure and radiation therapies are possible triggers of pemphigus vulgaris in predisposed patients. For the much rarer pemphigus foliaceus, UV exposure is of particular importance. Thiols and phenols are drugs that can induce pemphigus usually resembling pemphigus foliaceus clinically. Age is the most important risk factor of bullous pemphigoid. In addition, in bullous pemphigoid associations with dipeptidyl peptidase 4 inhibitors, programmed cell death protein‑1 or programmed death-ligand‑1 inhibitors as well as neurological diseases are particularly relevant. Severe mucosal damage, certain drugs and in particular cases neoplasms might play a role in mucous membrane pemphigoid.

CONCLUSION

Knowing possible trigger factors facilitates a timely diagnosis upon initial manifestation and supports the prevention of relapse of bullous autoimmune dermatoses.

[Rare variants of pemphigoid diseases]

Pemphigoid diseases comprise a heterogeneous group of subepidermal autoimmune blistering dermatoses characterized by autoantibodies against structural proteins of the dermal-epidermal junction. Recent decades have witnessed a significant surge in the incidence of these diseases, which, in addition to general aging of the population, can be attributed to the availability of precise diagnostic methods and improved knowledge of the clinical and immunopathological spectrum. While bullous pemphigoid, mucous membrane pemphigoid, and linear IgA disease account for most pemphigoid disorders, less frequent, presumably underdiagnosed variants are increasingly becoming relevant for clinicians. These include epidermolysis bullosa acquisita, anti-p200 pemphigoid, pemphigoid gestationis, lichen planus pemphigoides, and recently defined entities such as IgM pemphigoid and Orf-induced pemphigoid. Accurate characterization and differentiation of these subtypes are not only of diagnostic relevance but may also be associated with therapeutic and prognostic implications for affected individuals. Due to the rarity of these diseases, no controlled prospective clinical trials currently exist, making their diagnosis and therapy challenging.

[Bullous autoimmune dermatoses of the mucous membranes]

Autoimmune bullous diseases (AIBD) comprise a group of organ-specific autoimmune diseases which are characterised by the production of autoantibodies against adhesion molecules and structural proteins of skin and mucosae. Depending on the target protein, AIBD are classified into intraepidermal (pemphigus group) and subepidermal (pemphigoid group, epidermolysis bullosa acquisita, dermatitis herpetiformis) blistering disorders. Depending on the clinical entity, patients can develop blisters, pustules, erosions, and erythema on the skin and mucosae.

The relevance of complement in pemphigoid diseases: A critical appraisal

Pemphigoid diseases are autoimmune chronic inflammatory skin diseases, which are characterized by blistering of the skin and/or mucous membranes, and circulating and tissue-bound autoantibodies. The well-established pathomechanisms comprise autoantibodies targeting various structural proteins located at the dermal-epidermal junction, leading to complement factor binding and activation. Several effector cells are thus attracted and activated, which in turn inflict characteristic tissue damage and subepidermal blistering. Moreover, the detection of linear complement deposits in the skin is a diagnostic hallmark of all pemphigoid diseases. However, recent studies showed that blistering might also occur independently of complement. This review reassesses the importance of complement in pemphigoid diseases based on current research by contrasting and contextualizing data from in vitro, murine and human studies.

Type XVII collagen: Relevance of distinct epitopes, complement-independent effects, and association with neurological disorders in pemphigoid disorders

Pemphigoid diseases (PD) are autoimmune skin blistering diseases characterized by autoantibodies directed against proteins of the cutaneous basement membrane zone (BMZ). One of the major antigens is type XVII collagen (BP180), a transmembrane glycoprotein, which is targeted in four PDs: bullous pemphigoid, mucous membrane pemphigoid, linear IgA dermatosis, and pemphigoid gestationis. To date, different epitopes on BP180 have been described to be recognized by PD disease patients’ autoantibodies. Different BP180 epitopes were associated with distinct clinical phenotypes while the underlying mechanisms are not yet fully understood. So far, the main effects of anti-BP180 reactivity are mediated by Fcγ-receptors on immune cells. More precisely, the autoantibody–antigen interaction leads to activation of complement at the BMZ and infiltration of immune cells into the upper dermis and, by the release of specific enzymes and reactive oxygen species, to the degradation of BP180 and other BMZ components, finally manifesting as blisters and erosions. On the other hand, inflammatory responses independent of Fcγ-receptors have also been reported, including the release of proinflammatory cytokines and internalization and depletion of BP180. Autoantibodies against BP180 can also be found in patients with neurological diseases. The assumption that the clinical expression of PD depends on epitope specificity in addition to target antigens, autoantibody isotypes, and antibody glycosylation is supported by the observation that epitopes of PD patients differ from those of PD patients. The aim of the present review is to describe the fine specificities of anti-BP180 autoantibodies in different PDs and highlight the associated clinical differences. Furthermore, the direct effects after binding of the autoantibodies to their target are summarized.

Blasenbildende Autoimmundermatosen – Klinik, Diagnostik und neue Therapieansätze

Diese Arbeit gibt eine Übersicht über die Gruppe blasenbildender Autoimmundermatosen und stellt deren wichtigste Vertreter, das bullöse Pemphigoid, den Pemphigus vulgaris sowie den Pemphigus foliaceus, vor. Die häufigste der insgesamt seltenen blasenbildenden Autoimmundermatosen ist das bullöse Pemphigoid (BP). Es betrifft vor allem Patienten jenseits des 60. Lebensjahrs. Charakterisiert ist es typischerweise durch das Auftreten praller Blasen, die mit einem heftigen Juckreiz einhergehen. Ein längeres, sogenanntes prämonitorisches Stadium ohne Blasenbildung ist nicht ungewöhnlich. Es gibt außerdem Varianten mit anderem Erscheinungsbild wie das lokalisierte BP. Der diagnostische Goldstandard ist die direkte Immunfluoreszenzmikroskopie einer periläsional entnommenen Hautbiopsie, welche lineare Ablagerungen von IgG und C3 an der Basalmembran zeigt. Vervollständigt wird die Diagnostik durch die indirekte Immunfluoreszenzmikroskopie sowie weiterführende ELISA-Untersuchungen, mittels derer zirkulierende Autoantikörper im Patientenserum nachgewiesen werden können. Das wichtigste Zielantigen ist BP180, ein hemidesmosomales, von Keratinozyten exprimiertes Protein. Ergänzend kann eine histopathologische Untersuchung erfolgen, die allerdings nur Hinweise zur Spaltebene und zum (meist Eosinophilen-dominierten) Infiltratmuster geben kann und alleine nicht zur Diagnosestellung ausreicht. Die Pathogenese des BP ist Gegenstand der wissenschaftlichen Diskussion. Medikamente wie Dipeptidylpeptidase-4-Inhibitoren können Auslöser sein; Assoziationen zu neurologischen Erkrankungen finden sich häufig. Entsprechend aktueller Leitlinien wird das BP mit topischen bzw. systemischen Glukokortikoiden ggf. in Kombination mit Doxyzyklin, Dapson oder einem Immunsuppressivum behandelt. Bei Therapieresistenz werden intravenöse Immunglobuline oder der anti-CD-20-Antikörper Rituximab eingesetzt. Aufgrund einer vergleichsweise hohen Mortalität bedingt durch Patientenalter und iatrogener Immunsuppression werden neue Therapieansätze gesucht. Fallserien, Kohortenanalysen und Phase 1-/2-Studien mit anti-IgE-Antikörpern und Inhibitoren der eosinophilen Granulozyten sowie des Komplementsystems zeigen teils vielversprechende Effekte. Die wichtigsten Vertreter der Pemphiguserkrankungen sind der Pemphigus vulgaris (PV), der Pemphigus foliaceus (PF) und der sehr seltene paraneoplastische Pemphigus (PNP). Klinisch präsentiert sich der PV mit meist enoralen Schleimhauterosionen und teilweise zusätzlichen Erosionen an der freien Haut. Der PF manifestiert sich nur an der freien Haut. Wie beim BP wird die Diagnose mittels direkter Immunfluoreszenzmikroskopie gestellt, welche beim PV und PF netzförmige Ablagerungen von IgG und C3 innerhalb der Epidermis zeigt. Die häufigsten Zielantigene sind die Desmogleine 1 und 3. Genetische Prädispositionen für den PV und PF sind bekannt und Grund für eine global unterschiedliche Häufigkeit. Der PNP ist immer mit einer malignen Erkrankung assoziiert und von einem progredienten Verlauf mit hoher Mortalität geprägt. Therapeutisch erfordern die Pemphiguserkankungen oft aggressivere Ansätze als das BP. Neben systemischen Glukokortikoiden und Immunsuppressiva wird für den PV und PF der anti-CD-20-Antikörper Rituximab empfohlen. Neue Therapieansätze sind die Hemmung der Bruton-Tyrosinkinase sowie des neonatalen Fc-Rezeptors (FcRN). In einer Phase 2-Studie zeigte Efgartigimod, ein Antagonist des FcRN, eine hohe Therapieeffektivität für Patienten mit PV und PF.

Case report: bullous pemphigoid development underlies dystrophic epidermolysis bullosa disease worsening

Autoimmune response to cutaneous basement membrane components superimposed on a genetic skin fragility disease, hereditary epidermolysis bullosa (EB), has been described, but its effects on disease course remain unclear. We report a 69-year-old individual with congenital skin fragility and acral trauma-induced blistering that had suddenly worsened with the onset of severe itch and diffuse spontaneous inflammatory blisters. Next-generation sequencing identified compound heterozygous null and missense COL7A1 mutations, allowing the diagnosis of recessive dystrophic EB. However, the patient’s clinical history prompted us to investigate whether he might have developed a pathological autoimmune response against basement membrane components. Tissue-bound and circulating IgG antibodies to the major bullous pemphigoid (BP) antigen, BP180, were detected in the patient’s skin and serum, respectively, consistent with a diagnosis of BP. Corticosteroid therapy was initiated resulting in remission of BP manifestations. EB patients presenting rapid disease worsening should be investigated for the development of a concomitant autoimmune blistering disease.

Successful Treatment of Bullous Pemphigoid Lesions by Berberine Stamp Therapy: A Case Report and Literature Review

Bullous pemphigoid (BP) is a life-threatening autoimmune disease of the skin that is mainly characterized by a large range of tension blisters and intense itching of the skin. The 1-year mortality rate of BP was 23.5%. Superinfection caused by skin lesion ulceration is one of the important causes of disease death. Therefore, it is challenging to control infection and improve skin wound healing. Here, we report the case of an elderly woman who presented with BP and involved the oral mucosa. The patient was successfully treated with hormones combined with topical berberine, and 95% of the patients’ lesions healed completely after 1 month. In addition, we inductively analyzed the current treatments for BP to provide a reference for BP clinical treatment.

Unmet Medical Needs in Chronic, Non-communicable Inflammatory Skin Diseases

An estimated 20-25% of the population is affected by chronic, non-communicable inflammatory skin diseases. Chronic skin inflammation has many causes. Among the most frequent chronic inflammatory skin diseases are atopic dermatitis, psoriasis, urticaria, lichen planus, and hidradenitis suppurativa, driven by a complex interplay of genetics and environmental factors. Autoimmunity is another important cause of chronic skin inflammation. The autoimmune response may be mainly T cell driven, such as in alopecia areata or vitiligo, or B cell driven in chronic spontaneous urticaria, pemphigus and pemphigoid diseases. Rare causes of chronic skin inflammation are autoinflammatory diseases, or rheumatic diseases, such as cutaneous lupus erythematosus or dermatomyositis. Whilst we have seen a significant improvement in diagnosis and treatment, several challenges remain. Especially for rarer causes of chronic skin inflammation, early diagnosis is often missed because of low awareness and lack of diagnostics. Systemic immunosuppression is the treatment of choice for almost all of these diseases. Adverse events due to immunosuppression, insufficient therapeutic responses and relapses remain a challenge. For atopic dermatitis and psoriasis, a broad spectrum of innovative treatments has been developed. However, treatment responses cannot be predicted so far. Hence, development of (bio)markers allowing selection of specific medications for individual patients is needed. Given the encouraging developments during the past years, we envision that many of these challenges in the diagnosis and treatment of chronic inflammatory skin diseases will be thoroughly addressed in the future.