A systematic review with pooled analysis of clinical presentation and immunodiagnostic testing in mucous membrane pemphigoid: association of anti-laminin-332 IgG with oropharyngeal involvement and the usefulness of ELISA

The Role of Serology in the Diagnosis of Ocular Predominant Mucous Membrane Pemphigoid and the Search for an Ocular-Specific Autoantigen

Ocular predominant mucous membrane pemphigoid (oMMP) is a severe subtype of MMP that can lead to scarring and blindness. While conjunctival biopsy for direct immunofluorescence (DIF) is considered the gold standard for diagnosis, limited sensitivity results in a false-negative rate upwards of 40%. Likewise, it remains unclear to what extent a negative biopsy, whether false-negative or true-negative, results in a different prognosis, with patients previously termed "pseudopemphigoid" demonstrating comparable disease progression. Serologic testing allows for a less invasive means to demonstrate circulating autoantibodies against known autoantigens in pemphigoid diseases. Patients with MMP, particularly oMMP, however, typically demonstrate low titers of circulating autoantibodies, limiting the diagnostic utility of these tests. The autoantigen integrin β4 has been previously reported to be a specific marker of pure ocular MMP, while in the majority of patients with oMMP, the identified target antigens are BP180 (type XVII collagen) and laminin 332. Recent studies have, however, demonstrated inconsistent reactivity and specificity for integrin β4 as an ocular-specific marker in MMP. Herein, we review the role of serologic testing in the diagnosis and prognosis of oMMP, as well as the current understanding of autoantigens in oMMP.Abbreviations: BMZ - basement membrane zone, DIF - direct immunofluorescence, IIF - indirect immunofluorescence, MMP - mucous membrane pemphigoid, oMMP - ocular predominant mucous membrane pemphigoid.

Intravenous Ig Ameliorates Disease in a Murine Model of Anti-Laminin 332 Mucous Membrane Pemphigoid

Intravenous Ig (IVIg) is used to treat mucous membrane pemphigoid, although its therapeutic effectivity is not sufficiently supported by randomized controlled clinical trials, and its mode of action is only insufficiently understood. We have examined the effect of IVIg in a mouse model of anti-laminin 332 mucous membrane pemphigoid and found that IVIg ameliorates both cutaneous and mucosal inflammatory lesions. Our investigation into the modes of action of IVIg in mucous membrane pemphigoid indicated effective anti-inflammatory mechanisms beyond the enhanced degradation of IgG mediated through inhibition of the FcRn. Our results suggest that IVIg curbs the activation of neutrophils at several levels. This includes a direct, immediate inhibitory effect on neutrophil activation by immune complexes but not C5a, which blunts the release of ROS and leukotriene B4 from neutrophils. IVIg also suppresses the formation of neutrophil extracellular traps in response to calcium ion ionophore. In vivo treatment with IVIg altered the transcriptome of blood leukocytes and bone marrow neutrophils toward less proinflammatory phenotypes. Collectively, our results support the effectivity of IVIg in the treatment of mucous membrane pemphigoid and indicate that effects on neutrophils at multiple levels may significantly contribute to its therapeutic effects.

Anti-α6β4 integrin autoantibodies inhibit the binding of laminins to α6β4 integrin in patients with pemphigoid and affect the gastrointestinal tract

BACKGROUND

Anti-α6β4 integrin autoantibodies can be observed in some patients with mucous membrane pemphigoid. We have previously identified anti-α6β4 integrin extracellular domain autoantibodies together with anti-BP180 NC16A antibodies in a patient with DPP-4 inhibitor-induced bullous pemphigoid. However, the significance and impact of anti-α6β4 integrin antibodies are unknown.

OBJECTIVES

To characterize anti-α6β4 integrin extracellular domain autoantibodies in pemphigoid patients, to determine whether these antibodies inhibit laminin-α6β4 integrin binding and to observe their systemic effects.

METHODS

Anti-α6β4 integrin autoantibodies were analysed by staining cells expressing the extracellular region of α6β4 integrin with sera from 20 patients with pemphigoid. The anti-α6β4 integrin autoantibodies were characterized using different transfectants. The binding of laminins to α6β4 integrin was studied using cells expressing the activated conformation of α6β4 integrin and the inhibitory effect of the autoantibodies on the binding of laminins to α6β4 integrin was tested. Trends in antibody titres and clinical symptoms were quantified and analysed.

RESULTS

IgG autoantibodies against the extracellular domain of anti-α6β4 integrin were found in some patients with pemphigoid. Laminin binding to α6β4 integrin was observed in the active conformation of α6β4 integrin, and serum from a patient with a high titre of anti-α6β4 integrin antibodies inhibited the binding of both laminin-511 and laminin-332 to α6β4 integrin. α6β4 integrin is expressed on the basement membrane of both skin and small intestine, and exfoliation was observed in the patient's epidermis and small intestinal epithelium. A reduction in the titre of the anti-α6β4 integrin antibody was associated with improvement in both skin and gastrointestinal symptoms.

CONCLUSIONS

This study demonstrated the presence of anti-α6β4 integrin extracellular domain-specific autoantibodies in some patients with pemphigoid. In addition, these autoantibodies showed inhibitory activity on α6β4 integrin-laminin binding. Anti-α6β4 integrin antibodies can affect the gastrointestinal tract as well as the skin and oral mucosa.

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.

Anti-Laminin 332-Type Mucous Membrane Pemphigoid

Anti-laminin (LM) 332-type mucous membrane pemphigoid (MMP) is a rare autoimmune bullous disease and was originally discovered as anti-epiligrin cicatricial pemphigoid. Anti-LM332-type MMP has clinical manifestations similar to those of other types of MMP and can only be distinguished through the detection of circulating autoantibodies against LM332. Our group and others have established a number of immunological methods with varying sensitivity and specificity for detection of anti-LM332 autoantibodies; however, none of the established methods has been widely used for clinical diagnosis. There is currently no unified standard treatment, and it is very difficult to completely cure anti-LM332-type MMP. In addition, an increasing body of evidence suggests that there may be a strong correlation between anti-LM332-type MMP and tumors. In this article, we review the current progression of diagnosis and treatment of anti-LM332-type MMP, as well as the possible correlation between anti-LM332-type MMP and tumors.

Case report: A case of anti-laminin 332 mucous membrane pemphigoid associated with severe pharyngolaryngeal involvement

A 74-year-old woman presented with a 30-day history of blisters and erosions in the oral cavity, trunk, and left eye conjunctival mucosa, also reporting a weight loss of 15 kg in the last 3 months. Histopathological examination showed subepidermal blisters and lymphocytic infiltrates with rare eosinophils in the superficial dermis. Direct immunofluorescence showed linear deposits of IgG and C3 along the dermal-epidermal junction and salt-split skin indirect immunofluorescence confirmed the presence of linear deposits of IgG along the blister floor. Indirect immunofluorescence revealed antibodies against laminin 332 using recombinant laminin 332 expressed in human HEK293 cells, and commercial ELISA kits (Euroimmun, Padova, Italy) did not reveal antibodies against BP230 and BP180 antigens. Anti-laminin 332 mucous membrane pemphigoid (MMP), a condition often associated with a hidden neoplasm, was diagnosed. In our case, the paraneoplastic nature of MMP was excluded. Thus, topical treatment with triamcinolone acetonide 0.1% in orabase once daily for 30 days, oral prednisone 0.75 mg/kg/day and rituximab were started to relieve symptoms. Conjunctival, nasal and oral erosions improved, as well as skin lesions, but later the patient was tracheotomized due to respiratory distress linked to the appearance of pharyngolaryngeal synechiae.

A Probing of the Issue of Detecting IgG, IgG4 and IgA Antibodies to Laminin 332 Epitopes in Mucous Membrane Pemphigoid: A Clinical-Laboratory Experience of a Single Central European University Dermatology Department

Purpose

Mucous membrane pemphigoid (MMP) is a very rare autoimmune bullous disease, affecting predominantly the mucosae and characterized by autoantibodies to the epithelial basement membrane components. Laminin 332 (Ln-332) is one of the most probable antigens with association with malignancy. The laboratory diagnosis of Ln-332-mediated autoimmunity is troublesome. The aim here was to comparatively examine IgG, IgG4, and IgA autoantibodies specific to α3, β3 or γ2 subunits of Ln-322 in MMP patients using the BIOCHIP mosaic-based indirect immunofluorescence technique (IIF).

Patients and Methods

Sera from 15 MMP patients were studied. BIOCHIP mosaic-based Ln-332 IIF, direct immunofluorescence, ELISA tests for anti-BP180/BP20 IgG antibodies and statistical analyses were performed.

Results

Of all the 15 sera examined for IgG4 antibodies, only 1 (6.67%) reacted with the α3 chain, 0 with the β3 chain, and 0 with the γ2 chain. No positive reactivity was seen with the IgG and IgA antibodies. BIOCHIP mosaic-based IIF with Ln-332 showed 100% sensitivity, 8% specificity, 21% positive predictive value, and 100% negative predictive value in relation to the diagnostic gold standard of DIF. The concomitant malignancies were revealed in three cases.

Conclusion

The detection of antibodies to Ln-332 chains is occasional in Polish MMP sufferers. Still, the evaluation of IgG4 antibodies in MMP can reduce the false-negative results.

Gene expression profiling of laminin α3-blocked keratinocytes reveals an immune-independent mechanism of blistering

Laminin-332 pemphigoid is a rare and chronic autoimmune blistering disease which results in subepidermal blisters and erosive lesions predominantly localized to mucous membranes. As histologic inflammation is variable and non-complement-fixing IgG antibodies against laminin-332 are the predominant class of autoantibodies deposited at the epidermal basement membrane zone, we hypothesized that complement-independent pro-inflammatory and blistering pathways existed similarly to that previously shown in bullous pemphigoid. As autoantibodies to laminin α3 are most prevalent, we studied the major cellular response to blockade of laminin α3 using a well-characterized monoclonal antibody (P3H9-2). RNA-seq revealed upregulation of numerous desmosomal genes (DSG1, DSG3, DSC1, DSC3 and DSP) as well as KRT1 and KRT10. Additionally, P3H9-2-treated cells demonstrated downregulation of most hemidesmosomal genes. A pro-inflammatory response was not appreciated. Using pharmacological inhibitors, we identified both protein kinase C and NOTCH as key regulators of P3H9-2 induced differentiation. We lastly utilized 3D human skin equivalents to determine whether blockade of laminin α3 would lead to delayed blistering, consistent with keratinocyte differentiation. Significant blistering was noted after 72 h of treatment, with only minimal separation at 24 h. In summary, blockade of laminin α3 alters keratinocyte differentiation, representing a potential complement-independent mechanism of blistering.

Insights in clinical and diagnostic findings and treatment responses in patients with mucous membrane pemphigoid, a retrospective cohort study

BACKGROUND

The variable clinical severity of MMP often leads to a diagnostic and therapeutic delay.

OBJECTIVE

To describe the characteristics in a large cohort of patients with MMP.

METHODS

A retrospective review study of clinical and diagnostic characteristics and treatment response in 145 patients with MMP.

RESULTS

Monosite involvement was seen in 41.4% and multisite involvement in 58.6% patients. The oral mucosa was affected in 86.9%, followed by the ocular mucosa (30.3%), skin (26.2%), genital mucosa (25.5%), nasal mucosa (23.4%) and pharyngeal and/or laryngeal mucosa (17.2%). Ocular disease developed during disease course in 41.7% of patients with initially other mucosal site involvement. The malignancy rate was significantly higher in patients with autoantibodies against laminin-332 compared to MMP patients without laminin-332 autoantibodies (35.3% vs. 10.9%, p=0.007). Systemic immunosuppressive or immunomodulatory therapy were administered in 77.1% of the patients, mainly in patients with multisite involvement (p<0.001), ocular involvement (p<0.001) and pharyngeal and laryngeal involvement (p=0.002). The remaining patients (22.9%) received topical therapy. Adverse events were frequently reported.

LIMITATIONS

Retrospective design.

CONCLUSION

MMP presents with a heterogeneous clinical presentation and new symptoms may develop during the disease course. Cancer screening should be considered in MMP and in particular with autoantibodies against laminin-332.

Subunit-Specific Reactivity of Autoantibodies Against Laminin-332 Reveals Direct Inflammatory Mechanisms on Keratinocytes

Laminin-332 pemphigoid is a rare and severe autoimmune blistering disease, caused by IgG autoantibodies targeting laminin-332 in the dermal-epidermal basement zone. Laminin-332 pemphigoid is characterized by variable inflammatory infiltrate and the predominance of non-complement-fixing antibodies. Given these findings, we hypothesized that IgG autoantibodies to laminin-332 directly resulted in keratinocyte expression of inflammatory factors. We performed RNA-seq on primary human keratinocytes treated with IgG from patients with laminin-332 pemphigoid. Genes for numerous cytokines and chemokines were upregulated, including CSF2, CSF3, CXCL1, CXCL5, CXCL3, CXCL8, CXCL10, CXCL1, IL6, IL7, IL15, IL23, IL32, IL37, TGFB2 as well as metalloproteases. Considering the pro-inflammatory and proteolytic effect of autoantibodies from patients with laminin-332 pemphigoid identified in our initial experiment, we next questioned whether the reactivity against specific laminin subunits dictates the inflammatory and proteolytic keratinocyte response. Then, we treated keratinocytes with IgG from a separate cohort of patients with reactivity against individual subunits of laminin-332. We identified upregulation of IL-1α, IL-6, IL-8, CXCL1, MMP9, TSLP, and GM-CSF at the protein level, most notably in keratinocytes treated with IgG from laminin β3-reactive patients. We for the first time demonstrated a pro-inflammatory response, similar to that described in keratinocytes treated with IgG autoantibodies from patients with bullous pemphigoid, providing novel insight into the pathogenesis of laminin-332 pemphigoid and laminin-332 biology.

European Guidelines (S3) on diagnosis and management of mucous membrane pemphigoid, initiated by the European Academy of Dermatology and Venereology - Part II

This guideline has been initiated by the task force Autoimmune Blistering Diseases of the European Academy of Dermatology and Venereology, including physicians from all relevant disciplines and patient organizations. It is a S3 consensus-based guideline that systematically reviewed the literature on mucous membrane pemphigoid (MMP) in the MEDLINE and EMBASE databases until June 2019, with no limitations on language. While the first part of this guideline addressed methodology, as well as epidemiology, terminology, aetiology, clinical presentation and outcome measures in MMP, the second part presents the diagnostics and management of MMP. MMP should be suspected in cases with predominant mucosal lesions. Direct immunofluorescence microscopy to detect tissue-bound IgG, IgA and/or complement C3, combined with serological testing for circulating autoantibodies are recommended. In most patients, serum autoantibodies are present only in low levels and in variable proportions, depending on the clinical sites involved. Circulating autoantibodies are determined by indirect IF assays using tissue substrates, or ELISA using different recombinant forms of the target antigens or immunoblotting using different substrates. The major target antigen in MMP is type XVII collagen (BP180), although in 10-25% of patients laminin 332 is recognized. In 25-30% of MMP patients with anti-laminin 332 reactivity, malignancies have been associated. As first-line treatment of mild/moderate MMP, dapsone, methotrexate or tetracyclines and/or topical corticosteroids are recommended. For severe MMP, dapsone and oral or intravenous cyclophosphamide and/or oral corticosteroids are recommended as first-line regimens. Additional recommendations are given, tailored to treatment of single-site MMP such as oral, ocular, laryngeal, oesophageal and genital MMP, as well as the diagnosis of ocular MMP. Treatment recommendations are limited by the complete lack of high-quality randomized controlled trials.

European guidelines (S3) on diagnosis and management of mucous membrane pemphigoid, initiated by the European Academy of Dermatology and Venereology - Part I

This guideline on mucous membrane pemphigoid (MMP) has been elaborated by the Task Force for Autoimmune Blistering Diseases of the European Academy of Dermatology and Venereology (EADV) with a contribution of physicians from all relevant disciplines and patient organizations. It is a S3 consensus-based guideline encompassing a systematic review of the literature until June 2019 in the MEDLINE and EMBASE databases. This first part covers methodology, the clinical definition of MMP, epidemiology, MMP subtypes, immunopathological characteristics, disease assessment and outcome scores. MMP describes a group of autoimmune skin and mucous membrane blistering diseases, characterized by a chronic course and by predominant involvement of the mucous membranes, such as the oral, ocular, nasal, nasopharyngeal, anogenital, laryngeal and oesophageal mucosa. MMP patients may present with mono- or multisite involvement. Patients' autoantibodies have been shown to be predominantly directed against BP180 (also called BPAG2, type XVII collagen), BP230, laminin 332 and type VII collagen, components of junctional adhesion complexes promoting epithelial stromal attachment in stratified epithelia. Various disease assessment scores are available, including the Mucous Membrane Pemphigoid Disease Area Index (MMPDAI), the Autoimmune Bullous Skin disorder Intensity Score (ABSIS), the 'Cicatrising Conjunctivitis Assessment Tool' and the Oral Disease Severity Score (ODSS). Patient-reported outcome measurements (PROMs), including DLQI, ABQOL and TABQOL, can be used for assessment of quality of life to evaluate the effectiveness of therapeutic interventions and monitor disease course.

A Review of Acquired Autoimmune Blistering Diseases in Inherited Epidermolysis Bullosa: Implications for the Future of Gene Therapy

Gene therapy serves as a promising therapy in the pipeline for treatment of epidermolysis bullosa (EB). However, with great promise, the risk of autoimmunity must be considered. While EB is a group of inherited blistering disorders caused by mutations in various skin proteins, autoimmune blistering diseases (AIBD) have a similar clinical phenotype and are caused by autoantibodies targeting skin antigens. Often, AIBD and EB have the same protein targeted through antibody or mutation, respectively. Moreover, EB patients are also reported to carry anti-skin antibodies of questionable pathogenicity. It has been speculated that activation of autoimmunity is both a consequence and cause of further skin deterioration in EB due to a state of chronic inflammation. Herein, we review the factors that facilitate the initiation of autoimmune and inflammatory responses to help understand the pathogenesis and therapeutic implications of the overlap between EB and AIBD. These may also help explain whether corrections of highly immunogenic portions of protein through gene therapy confers a greater risk towards developing AIBD.

High frequency of upper aerodigestive tract manifestations in mucous membrane pemphigoid

OBJECTIVE

The objective of this study was to evaluate the frequency of upper aerodigestive tract involvement in patients with mucous membrane pemphigoid associated with desquamative gingivitis.

SUBJECTS AND METHODS

Data from 25 patients were collected by retrospective chart review. Their upper aerodigestive had been evaluated using a conventional flexible fiberscope. Oral disease activity was quantified on the basis of the Mucous Membrane Pemphigoid Disease Area Index activity score.

RESULTS

Lesions of the upper aerodigestive tract were confirmed in nine symptomatic patients (9/25, 36%), of which five (5/25, 20%) had laryngeal involvement. No lesions were seen in the asymptomatic patients on fiberscope examination. There was a statistically significant difference in the symptoms, high oral disease activity score, and linear IgA deposition on direct immunofluorescence between patients with and without upper aerodigestive tract lesions (p = .001, .001, .002, respectively).

CONCLUSION

The high frequency of considerable complications highlights the importance of confirming the presence of upper aerodigestive tract involvement in patients with mucous membrane pemphigoid having desquamative gingivitis. Signs including the presence of symptoms, high oral disease activity score, or linear IgA deposition on direct immunofluorescence might indicate a higher risk of upper aerodigestive tract involvement.

Evaluation of BP180-NC16A ELISA in exclusive oral pemphigoid diagnosis. A comparative study

OBJECTIVE

Aims of this study were to test the efficacy of anti-BP180-NC160 ELISA in the diagnosis of oral pemphigoid compared to the gold standard, represented by direct immunofluorescence and pathological examination, to correlate the antibody titers with the severity of the disease and the demographical data.

MATERIALS AND METHODS

Patients with a suspect of oral pemphigoid were enrolled and underwent biopsy and sera collection both, in order to perform histopathological examination, direct immunofluorescence and ELISA. The test outcomes were compared, and ELISA sensitivity, specificity, accuracy, and negative and positive predictive values were calculated.

RESULTS

ELISA showed good specificity (83.3%), while sensitivity was only 50%. A moderate correlation between antibody titers and disease severity was recorded.

CONCLUSIONS

Mucomembranous Pemphigoid is an autoimmune autoantibody-mediated blistering disease, often affecting exclusively the oral mucosa. Currently, the biopsy is required to diagnose this disease, but serological tests are also commonly employed during clinical practice as adjunctive tools. BP180-NC160 ELISA should be considered an ancillary diagnostic test in course of oral pemphigoid; direct immunofluorescence + histologic examination remains the diagnostic gold standard.

Japanese guidelines for the management of pemphigoid (including epidermolysis bullosa acquisita)

The pemphigoid group is a category of autoimmune subepidermal blistering diseases in which autoantibodies deposit linearly at the epidermal basement membrane zone (BMZ). The main subtypes of pemphigoid mediated by immunoglobulin G autoantibodies are bullous pemphigoid (BP), mucous membrane pemphigoid (MMP) and epidermolysis bullosa acquisita (EBA). To establish the first guidelines approved by the Japanese Dermatological Association for the management of pemphigoid diseases, the Committee for Guidelines for the Management of Pemphigoid Diseases (Including EBA) was founded as part of the Study Group for Rare Intractable Skin Diseases under the Ministry of Health, Labor and Welfare Research Project on Overcoming Intractable Diseases. These guidelines aim to provide current information for the management of BP, MMP and EBA in Japan. Based on evidence, the guidelines summarize the clinical and immunological manifestations, pathophysiologies, diagnostic criteria, disease severity determination criteria, treatment algorithms and treatment recommendations. Because of the rarity of these diseases, there are few clinical studies with a high degree of evidence, so several parts of these guidelines were established based on the opinions of the Committee. To further optimize these guidelines, periodic revision in line with the new evidence is necessary.

Keratinocyte footprint assay discriminates antilaminin-332 pemphigoid from all other forms of pemphigoid diseases

Background

Antilaminin‐332 mucous membrane pemphigoid is a chronic severe pemphigoid disease characterized by autoantibodies to laminin‐332. At present no commercial assay is available to demonstrate antilaminin‐332 antibodies, and diagnosis relies on in‐house techniques with limited sensitivities.

Objectives

In order to move, keratinocytes cultured in vitro secrete laminin‐332 to attach to the culture dish. In that way, they leave behind a unique footprint trail of laminin‐332. We aimed to develop a sensitive and specific laboratory assay to determine antilaminin‐332 autoantibodies in patient serum based on binding of patient IgG to these unique footprints.

Methods

Normal human keratinocytes were grown on glass coverslips and incubated with patient or control serum for 1 h. The binding of IgG was then investigated by immunofluorescence. After validating the test for its ability to identify antilaminin‐332 autoantibodies it was converted into a daily available test based on binding of IgG to dried coverslips that can be stored frozen. The staining patterns of sera from patients with antilaminin‐332 pemphigoid were then compared with those of sera from patients with other autoimmune bullous diseases and normal human sera.

Results

IgG of all antilaminin‐332 pemphigoid sera (n = 16) bound to laminin‐332 footprints, while all normal human controls (n = 55) were negative. From the sera of patients with other diseases (n = 72) four sera tested positive. The footprint assay was also positive for sera that were negative by salt‐split skin analysis, demonstrating that it is a very sensitive technique.

Conclusions

The keratinocyte footprint assay is a fast and specific assay to confirm or rule out the presence of antilaminin‐332 autoantibodies.

What's already known about this topic?

Antilaminin‐332 mucous membrane pemphigoid is a severe form of pemphigoid, and patients may have an increased risk of malignancies.

The diagnosis of antilaminin‐332 mucous membrane pemphigoid is complicated by the lack of specific commercial tests for antilaminin‐332 antibodies and can be confirmed only in specialized laboratories.

Keratinocytes in culture need laminin‐332 for adhesion and migration and therefore deposit it on the bottom of the culture dish.

What does this study add?

The keratinocyte footprint assay detects antilaminin‐332 autoantibodies in patient serum using the native laminin‐332 produced by cultured keratinocytes.

What is the translational message?

The keratinocyte footprint assay is a fast and specific assay to confirm or rule out the presence of antilaminin‐332 autoantibodies.

Linked Comment: https://doi.org/10.1111/bjd.18372.

https://doi.org/10.1111/bjd.18761 available online

Targeted Therapies for Autoimmune Bullous Diseases: Current Status

Autoimmune bullous skin disorders are rare but meaningful chronic inflammatory diseases, many of which had a poor or devastating prognosis prior to the advent of immunosuppressive drugs such as systemic corticosteroids, which down-regulate the immune pathogenesis in these disorders. Glucocorticoids and adjuvant immunosuppressive drugs have been of major benefit for the fast control of most of these disorders, but their long-term use is limited by major side effects such as blood cytopenia, osteoporosis, diabetes mellitus, hypertension, and gastrointestinal ulcers. In recent years, major efforts were made to identify key elements in the pathogenesis of autoimmune bullous disorders, leading to the identification of their autoantigens, which are mainly located in desmosomes (pemphigus) and the basement membrane zone (pemphigoids). In the majority of cases, immunoglobulin G, and to a lesser extent, immunoglobulin A autoantibodies directed against distinct cutaneous adhesion molecules are directly responsible for the loss of cell-cell and cell-basement membrane adhesion, which is clinically related to the formation of blisters and/or erosions of the skin and mucous membranes. We describe and discuss novel therapeutic strategies that directly interfere with the production and regulation of pathogenic autoantibodies (rituximab), their catabolism (intravenous immunoglobulins), and their presence in the circulation and extravascular tissues such as the skin (immunoadsorption), leading to a significant amelioration of disease. Moreover, we show that these novel therapies have pleiotropic effects on various proinflammatory cells and cytokines. Recent studies in bullous pemphigoid suggest that targeting of immunoglobulin E autoantibodies (omalizumab) may be also beneficial. In summary, the introduction of targeted therapies in pemphigus and pemphigoid holds major promise because of the high efficacy and fewer side effects compared with conventional global immunosuppressive therapy.

Immunological methods for the diagnosis of oral mucosal diseases

Immunological methods, which have been widely used in autoimmune blistering diseases (AIBDs) of the oral mucosa, can also be adopted as auxiliary diagnostic tools in oral lichen planus (OLP) and discoid lupus erythematosus (DLE). AIBDs, characterized by autoantibodies against structural proteins of keratinocytes or the basement membrane zone, clinically present as blisters and erosions of the oral mucosa. When atypical lesions occur, OLP or DLE may be confused with AIBDs. The improvement of diagnostic accuracy is necessary due to the significant differences in treatment and prognosis among these diseases. A variety of immunological methods are used for qualitative and quantitative detection of target antigens and autoantibodies. These methods can evaluate efficacy of treatment, monitor diseases and guide treatment decisions. In this review, we discuss the application of immunofluorescence, biochemical tests, and protein microarrays for AIBDs, OLP and DLE, as well as the differential diagnostic methods using immunological tests.

A sensitive and specific assay for the serological diagnosis of antilaminin 332 mucous membrane pemphigoid

BACKGROUND

Antilaminin 332 mucous membrane pemphigoid (MMP) is an autoimmune subepidermal blistering disease with predominant mucosal involvement and autoantibodies against laminin 332. Malignancies have been associated with this disease; however, no standardized detection system for antilaminin 332 serum antibodies is widely available.

OBJECTIVES

Development of a sensitive and specific assay for the detection of antilaminin 332 antibodies.

METHODS

An indirect immunofluorescence (IF) assay using recombinant laminin 332 was developed and probed with a large number of antilaminin 332 MMP patient sera (n = 93), as well as sera from patients with antilaminin 332-negative MMP (n = 153), bullous pemphigoid (n = 20), pemphigus vulgaris (n = 20) and noninflammatory dermatoses (n = 22), and healthy blood donors (n = 100).

RESULTS

In the novel IF assay, sensitivities with the laminin 332 heterotrimer and the individual α3, β3 and γ2 chains were 77%, 43%, 41% and 13%, respectively, with specificities of 100% for each substrate. The sensitivity for the heterotrimer increased when an anti-IgG4 enriched antitotal IgG conjugate was applied. Antilaminin 332 reactivity paralleled disease activity and was associated with malignancies in 25% of patients with antilaminin 332 MMP.

CONCLUSIONS

The novel IF-based assay will facilitate the serological diagnosis of antilaminin 332 MMP and may help to identify patients at risk of a malignancy.

The spectrum of histopathologic findings in pemphigoid: Avoiding diagnostic pitfalls

BACKGROUND

Bullous pemphigoid (BP) is an autoimmune vesiculobullous dermatitis that primarily affects the elderly and presents with tense, fluid-filled blisters. The histological hallmark on routine hematoxylin & eosin (H&E)-stained specimens is a subepidermal blister with luminal eosinophils. However, there are histologic variants than can produce diagnostic confusion.

METHODS

All immunofluorescence reports from an independent certified dermatopathology laboratory (2006-2015) were inspected, and those with findings consistent with an autoimmune subepidermal blistering process were selected. Seventy-seven cases were identified, and the corresponding H&E-stained specimens were reviewed by two dermatopathologists who tabulated the histopathologic findings.

RESULTS

Just over half of biopsies showed subepidermal clefting (54%). The histologic variants included: urticarial or eczematous findings (17%), partial or complete re-epithelialization (28%), and epidermal necrosis (7%).

CONCLUSION

While re-epithelialization of subepidermal blisters is a commonly accepted phenomenon, there are no published data demonstrating its incidence. Because only half of the biopsies showed the classic subepidermal blister, it is important to be aware of the spectrum of histopathologic findings that occur in this disease. Specifically, the presence of an intraepidermal blister and/or epidermal necrosis on routine H&E-stained specimens does not preclude the diagnosis of pemphigoid.

Autoimmune Subepidermal Bullous Diseases of the Skin and Mucosae: Clinical Features, Diagnosis, and Management

Autoimmune subepidermal blistering diseases of the skin and mucosae constitute a large group of sometimes devastating diseases, encompassing bullous pemphigoid, gestational pemphigoid, mucous membrane pemphigoid, epidermolysis bullosa acquisita, and anti-p200 pemphigoid. Their clinical presentation is polymorphic. These autoimmune blistering diseases are associated with autoantibodies that target distinct components of the basement membrane zone of stratified epithelia. These autoantigens represent structural proteins important for maintenance of dermo-epidermal integrity. Bullous pemphigoid (BP) is the most common subepidermal autoimmune blistering disease of the skin and mucosae. Although the disease typically presents with a generalized blistering eruption associated with itch, atypical variants with either localized bullous lesions or "non-bullous" presentations are observed in approximately 20% of patients. A peculiar form of BP typically associated with pregnancy is pemphigoid gestationis. In anti-p200 pemphigoid, patients present with tense blisters on erythematosus or normal skin resembling BP, with a predilection for acral surfaces. These patients have antibodies targeting the 200-kDa basement membrane protein. Epidermolysis bullosa is a rare autoimmune blistering disease associated with autoantibodies against type VII collagen that can have several phenotypes including a classical form mimicking dystrophic epidermolysis bullosa, an inflammatory presentation mimicking BP, or mucous membrane pemphigoid-like lesions. Mucous membrane pemphigoid (MMP) is the term agreed upon by international consensus for an autoimmune blistering disorder, which affects one or more mucous membrane and may involve the skin. The condition involves a number of different autoantigens in the basement membrane zone. It may result in severe complications from scarring, such as blindness and strictures. Diagnosis of these diseases relies on direct immunofluorescence microscopy studies and immunoserological assays. Management of affected patients is often challenging. We will here review the clinical and immunopathological features as well as the pathophysiology of this group of organ-specific autoimmune diseases. Finally, we will discuss the diagnostic approach and the principles of management in clinical practice.

Paraneoplastic mucous membrane pemphigoid with ocular and laryngeal involvement

A 73-year-old woman was treated 8 years previously for synchronous breast and uterine neoplasms. She presented with a severe sore throat, odynophagia, dysphonia, dyspnoea, ocular irritation and weight loss over the last 3 months. Physical examination revealed ulcerations in the oral cavity, posterior pharyngeal wall and supraglottic larynx, nasal crusting, bilateral conjunctivitis and three cutaneous blisters. A diagnosis of anti-laminin 5 mucous membrane pemphigoid was retained, based on skin biopsy, direct immunofluorescence and immunoprecipitation. A positron emission tomography (PET)-CT detected multiple adenopathies. Cytology revealed adenocarcinoma with an immunocytology compatible with a breast origin and this was considered as a late metastatic recurrence of her previous breast cancer. A treatment of prednisone, dapsone and hormonotherapy was introduced, but intravenous immunoglobulin and rituximab were added due to new mucosal lesions. Despite treatment, a posterior laryngeal scar and bilateral symblepharon were developed. After 3 years, the patient is still alive and reports a satisfactory quality of life.

Experimental Laminin 332 Mucous Membrane Pemphigoid Critically Involves C5aR1 and Reflects Clinical and Immunopathological Characteristics of the Human Disease

Mucous membrane pemphigoid is an autoantibody-mediated disease predominantly affecting the oral cavity, pharynx, and conjunctiva. Conjunctival lesions may lead to impaired vision and, finally, blindness. About 25% of mucous membrane pemphigoid patients generate autoantibodies against the α3 chain of laminin 332 (LAMα3), a structural protein of epidermal/epithelial basement membranes. Here, we established a mouse model by the passive transfer of rabbit IgG against the murine homologs of two immunodominant fragments in adult C57BL/6 mice (mLAMα3). After repeated subcutaneous injections of anti-mLAMα3 IgG erosions and crusts occurred predominantly around the snout, eyes, and on ears. Conjunctival and oral/pharyngeal lesions with subepithelial splitting were found in 80% and 100% of mice, respectively. In contrast, disease development was abrogated in FcRγ chain-deficient mice and markedly reduced in C5aR1-deficient mice. Furthermore, wild-type mice injected with anti-mLAMα3 F(ab')2 were completely protected. Our findings suggest a crucial codominant role of FcRγ and complement activation of the anti-mLAMα3 IgG-induced mouse model of mucous membrane pemphigoid. This model will help further discover the pathomechanisms of this devastating disease. Furthermore, it may be of use to explore the effect of urgently needed more specific anti-inflammatory mediators on mucosal and skin lesions in autoantibody-mediated diseases.