Pemphigoid diseases are a group of well defined autoimmune disorders that are characterised by autoantibodies against structural proteins of the dermal-epidermal junction and, clinically, by tense blisters and erosions on skin or mucous membranes close to the skin surface. The most common of these diseases is bullous pemphigoid, which mainly affects older people and the reported incidence of which in Europe has more than doubled in the past decade. Prognosis and treatments vary substantially between the different disorders and, since clinical criteria are usually not sufficient, direct immunofluorescence microscopy of a perilesional biopsy specimen or serological tests are needed for exact diagnosis. In eight pemphigoid diseases the target antigens have been identified molecularly, which has allowed the development of standard diagnostic assays for detection of serum autoantibodies-some of which are commercially available. In this Seminar we discuss the clinical range, diagnostic criteria, diagnostic assay systems, and treatment options for this group of diseases.

Our scientific knowledge of pemphigus has dramatically progressed in recent years. However, despite the availability of various therapeutic options for the treatment of inflammatory diseases, only a few multicenter controlled trials have helped to define effective therapies in pemphigus. A major obstacle in comparing therapeutic outcomes between centers is the lack of generally accepted definitions and measurements for the clinical evaluation of pemphigus patients. Common terms and endpoints of pemphigus are needed so that experts in the field can accurately measure and assess disease extent, activity, severity, and therapeutic response, and thus facilitate and advance clinical trials This consensus statement from the International Pemphigus Committee represents two years of collaborative efforts to attain mutually acceptable common definitions for pemphigus. These should assist in development of consistent reporting of outcomes in future studies.

Pemphigus is a group of IgG-mediated autoimmune diseases of stratified squamous epithelia, such as the skin and oral mucosa, in which acantholysis (the loss of cell adhesion) causes blisters and erosions. Pemphigus has three major subtypes: pemphigus vulgaris, pemphigus foliaceus and paraneoplastic pemphigus. IgG autoantibodies are characteristically raised against desmoglein 1 and desmoglein 3, which are cell–cell adhesion molecules found in desmosomes. The sites of blister formation can be physiologically explained by the anti-desmoglein autoantibody profile and tissue-specific expression pattern of desmoglein isoforms. The pathophysiological roles of T cells and B cells have been characterized in mouse models of pemphigus and patients, revealing insights into the mechanisms of autoimmunity. Diagnosis is based on clinical manifestations and confirmed with histological and immunochemical testing. The current first-line treatment is systemic corticosteroids and adjuvant therapies, including immunosuppressive agents, intravenous immunoglobulin and plasmapheresis. Rituximab, a monoclonal antibody against CD20+ B cells, is a promising therapeutic option that may soon become first-line therapy. Pemphigus is one of the best-characterized human autoimmune diseases and provides an ideal paradigm for both basic and clinical research, especially towards the development of antigen-specific immune suppression treatments for autoimmune diseases.

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Complement is an ancient danger-sensing system that contributes to host defense, immune surveillance and homeostasis. C5a and its G protein–coupled receptor mediate many of the proinflammatory properties of complement. Despite the key role of C5a in allergic asthma, autoimmune arthritis, sepsis and cancer, knowledge about its regulation is limited. Here we demonstrate that IgG1 immune complexes (ICs), the inhibitory IgG receptor FcγRIIB and the C-type lectin–like receptor dectin-1 suppress C5a receptor (C5aR) functions. IgG1 ICs promote the association of FcγRIIB with dectin-1, resulting in phosphorylation of Src homology 2 domain–containing inositol phosphatase (SHIP) downstream of FcγRIIB and spleen tyrosine kinase downstream of dectin-1. This pathway blocks C5aR-mediated ERK1/2 phosphorylation, C5a effector functions in vitro and C5a-dependent inflammatory responses in vivo, including peritonitis and skin blisters in experimental epidermolysis bullosa acquisita. Notably, high galactosylation of IgG N-glycans is crucial for this inhibitory property of IgG1 ICs, as it promotes the association between FcγRIIB and dectin-1. Thus, galactosylated IgG1 and FcγRIIB exert anti-inflammatory properties beyond their impact on activating FcγRs.

Bullous pemphigoid is the most common autoimmune subepidermal blistering disease of the skin and mucous membranes. This disease typically affects the elderly and presents with itch and localized or generalized bullous lesions. In up to 20% of affected patients, bullae may be completely absent, and only excoriations, prurigo-like lesions, eczematous lesions, urticated lesions and/or infiltrated plaques are observed. The disease is significantly associated with neurological disorders. The morbidity of bullous pemphigoid and its impact on quality of life are significant. So far, a limited number of national treatment guidelines have been proposed, but no common European consensus has emerged. Our consensus for the treatment of bullous pemphigoid has been developed under the guidance of the European Dermatology Forum in collaboration with the European Academy of Dermatology and Venereology. It summarizes evidence-based and expert-based recommendations.

Background Pemphigus encompasses a group of life-threatening autoimmune bullous diseases characterized by blis-

Patients and Methods: Epidemiologic data of patients diagnosed with an autoimmune bullous disease during this time period were registered and statistically evaluated. Diagnosis was based on the clinical picture and specific immunopathological findings. Only patients from Lower Franconia, a well-defined administrative region of Southern Germany, were included into this study. Results: During the study period, 41 patients with an autoimmune bullous disease were diagnosed, including 27 with bullous pemphigoid, 4 with pemphigoid gestationis and mucous membrane pemphigoid, 2 with dermatitis herpetiformis and linear IgA disease, and 1 with epidermolysis bullosa acquisita and pemphigus vulgaris, respectively. The highest incidence was calculated for bullous pemphigoid (13.4 per 1 million inhabitants per year) followed by pemphigoid gestationis (2.0) and mucous membrane pemphigoid (2.0). Patients with mucous membrane pemphigoid were found to have the highest mean age at disease onset (76 years) followed by patients with bullous pemphigoid (74 years). Conclusions: This is the first prospective study on the incidence of autoimmune bullous disorders. Subepidermal blistering autoimmune diseases were shown to be more frequent than previously reported for Central Europe. This is most likely due to improved diagnostic tools for and increased awareness of these diseases.