Autoimmune blistering diseases: Histologic meaning

Distinct impact of IgG subclass on autoantibody pathogenicity in different IgG4-mediated diseases

IgG4 is the least potent human IgG subclass for the FcγR-mediated antibody effector function. Paradoxically, IgG4 is also the dominant IgG subclass of pathogenic autoantibodies in IgG4-mediated diseases. Here, we show that the IgG subclass and Fc-FcγR interaction have a distinct impact on the pathogenic function of autoantibodies in different IgG4-mediated diseases in mouse models. While IgG4 and its weak Fc-FcγR interaction have an ameliorative role in the pathogenicity of anti-ADAMTS13 autoantibodies isolated from thrombotic thrombocytopenic purpura (TTP) patients, they have an unexpected exacerbating effect on anti-Dsg1 autoantibody pathogenicity in pemphigus foliaceus (PF) models. Strikingly, a non-pathogenic anti-Dsg1 antibody variant optimized for FcγR-mediated effector function can attenuate the skin lesions induced by pathogenic anti-Dsg1 antibodies by promoting the clearance of dead keratinocytes. These studies suggest that IgG effector function contributes to the clearance of autoantibody-Ag complexes, which is harmful in TTP, but beneficial in PF and may provide new therapeutic opportunity.

Spongiotic reaction patterns in autoimmune bullous dermatoses (Review)

Spongiosis or a spongiotic reaction pattern is the histological hallmark of intercellular epidermal edema, viewed as clear spaces within the epidermis. Although considered a histopathological term, spongiosis has clinical correlations, with the variable degrees of spongiotic reaction leading to different dermatological findings. This review aimed to highlight the spongiotic reactive patterns found in different autoimmune bullous dermatoses, considering the paucity of publications in this domain. The pathogenesis of spongiosis assumes the passage of extravasated edema fluid from the dermis into the epidermis, frequently accompanied by dermal inflammatory cells, and classification of the spongiotic reaction patterns, as well as their associated spongiotic dermatitis, take into consideration the type and distribution of these inflammatory cells. It is mandatory to consider different reactive processes, specific for other skin disorders, which act as simulants of different spongiotic patterns for the diagnosis. Considering the possible transient occurrence, the heterogeneity and non-specificity of the histopathological features of these diseases, the diagnosis is very complex, requiring clinicopathological correlations and additional analyses. A deep insight into spongiosis pathogeny may open the perspectives of a classification refinement of autoimmune bullous dermatoses.

Pemphigus foliaceus as a differential diagnosis in vesicobullous lesions

Given the challenge of clinical diagnosis of bullous skin lesions, this report aimed to discuss the histological changes, the presentation and clinical reasoning for diagnosis of these lesions. At the same time, the importance of the pathology was reviewed to identify these clinical scenarios. In this case report, we highlighted the clinical progression of a case of pemphigus foliaceus.

IgA Pemphigus in a Child – a Case Report

IgA pemphigus (IGAP) is a rare autoimmune bullous disease characterized by IgA deposits on keratinocyte cell surfaces. The IGAP is classified into: 1) subcorneal pustular dermatosis (SPD) type, and 2) intraepidermal neutrophilic (IEN) IgA dermatosis type. So far, only 9 children with IGAP have been described in the literature, of whom only 3 with SPD type. We report a 3-year-old boy with SPD type of IGAP. Clinically, he presented with pruritic vesicles, pustules and erosions on the face, trunk, groin area, and extremities. Histopathology showed subcorneal pustules containing a few acantholytic cells. Direct immunofluorescence (DIF) test of Tzanck smear showed intercellular IgA deposits on the surface of the groups of epidermal cells. Oral dapsone and prednisone induced remission after two weeks; the treatment was discontinued 11 months later, and complete remission was achieved during 19 months without any treatment. Direct immunofluorescence of Tzanck smear is a simple, sensitive, rapid and non-aggressive test, very suitable for the diagnosis of IGAP in children.

Immunohistochemical localization of basement membrane laminin 5 and collagen IV in adult linear IgA disease

BACKGROUND

Linear immunoglobulin A disease (LAD), also known as linear IgA bullous dermatosis, is an autoimmune disorder characterized by subepidermal bullae caused by IgA autoantibodies directed against several antigens located in the basement membrane zone of the skin. Laminin 5 (laminin-332) is considered a key component of the lamina lucida/lamina densa interface, which provides stable attachment of the epidermis to the dermis. Meanwhile, collagen IV is a major component of the lamina densa. Laminin 5 and collagen IV bind to the cell membrane and induce cytoskeletal rearrangements, which contribute to the basement membrane's final mat-like structure. The study aimed to evaluate the immunohistochemical staining of laminin 5 and collagen IV and to identify the site of blister formation in formalin-fixed, paraffin-embedded skin biopsies from adults with LAD.

METHODS

Skin biopsies from 20 adult patients with LAD were subjected to routine hematoxylin-eosin as well as immunohistochemical staining of collagen IV and laminin 5.

RESULTS

Linear staining was positive on the floor of the blister for laminin 5 in 65% and collagen IV in 90% of biopsies denoting that the site of separation in most cases of LAD is above the lamina densa.

CONCLUSIONS

The use of laminin 5 and collagen IV immunohistochemistry can be considered as an adjuvant diagnostic tool and may aid in the identification of the site of blister formation in routine skin biopsies in adults with LAD.

Oral mucosal manifestations of autoimmune skin diseases

A group of autoimmune diseases is characterised by autoantibodies against epithelial adhesion structures and/or tissue-tropic lymphocytes driving inflammatory processes resulting in specific pathology at the mucosal surfaces and the skin. The most frequent site of mucosal involvement in autoimmune diseases is the oral cavity. Broadly, these diseases include conditions affecting the cell-cell adhesion causing intra-epithelial blistering and those where autoantibodies or infiltration lymphocytes cause a loss of cell-matrix adhesion or interface inflammation. Clinically, patients present with blistering, erosions and ulcers that may affect the skin as well as further mucosal surfaces of the eyes, nose and genitalia. While the autoimmune disease may be suspected based on clinical manifestations, demonstration of tissue-bound and circulating autoantibodies, or lymphocytic infiltrates, by various methods including histological examination, direct and indirect immunofluorescence microscopy, immunoblotting and quantitative immunoassay is a prerequisite for definitive diagnosis. Given the frequency of oral involvement and the fact that oral mucosa is the initially affected site in many cases, the informed practitioner should be well acquainted with diagnostic and therapeutic aspects of autoimmune dermatosis with oral involvement. This paper reviews the pathogenesis and clinical presentation of these conditions in the oral cavity with a specific emphasis on their differential diagnosis and current management approaches.

Clinical relevance of autoantibodies in patients with autoimmune bullous dermatosis

The authors present their experience related to the diagnosis, treatment, and followup of 431 patients with bullous pemphigoid, 14 patients with juvenile bullous pemphigoid, and 273 patients with pemphigus. The detection of autoantibodies plays an outstanding role in the diagnosis and differential diagnosis. Paraneoplastic pemphigoid is suggested to be a distinct entity from the group of bullous pemphigoid in view of the linear C3 deposits along the basement membrane of the perilesional skin and the “ladder” configuration of autoantibodies demonstrated by western blot analysis. It is proposed that IgA pemphigoid should be differentiated from the linear IgA dermatoses. Immunosuppressive therapy is recommended in which the maintenance dose of corticosteroid is administered every second day, thereby reducing the side effects of the corticosteroids. Following the detection of IgA antibodies (IgA pemphigoid, linear IgA bullous dermatosis, and IgA pemphigus), diamino diphenyl sulfone (dapsone) therapy is preferred alone or in combination. The clinical relevance of autoantibodies in patients with autoimmune bullous dermatosis is stressed.

Diagnosis and treatment of pemphigus

Pemphigus is an autoimmune bullous disease, in which autoantibodies react with the cell–cell adhesion structures, desmosomes, causing blisters and erosions on the oral mucosa and skin. Pemphigus is divided into two major subtypes: pemphigus vulgaris and pemphigus foliaceus. Oral corticosteroids are the primary treatment modality for pemphigus, while other therapeutic options, such as steroid pulse therapy, immunosuppressants, intravenous immunoglobulins, plasmapheresis and anti-CD20 monoclonal antibody therapy, are occasionally employed. Immunosuppressants used to treat pemphigus include azathioprine, cyclophosphamide, cyclosporine, mycophenolate mofetil and mizoribine. In this review, we summarize the current concepts of immunotherapy for the treatment of pemphigus in the Japanese population.