Anti-Laminin 332-Type Mucous Membrane Pemphigoid

Diagnostic Techniques in Autoimmune Blistering Diseases

Autoimmune blistering diseases (AIBD) comprise a heterogeneous group of uncommon disorders of the skin and mucous membranes, characterised by antibodies targeting structural proteins within epithelial tissue and the underlying basement membrane. There can be significant overlap in clinical presentation of these diseases and accurate diagnosis relies on the detection and characterisation of relevant autoantibodies. Immunofluorescence provides the gold-standard diagnostic tool for these diseases, identifying both tissue-bound autoantibodies in biopsy material using direct immunofluorescence and circulating antibodies in serum through indirect immunofluorescence. Following advances in the identification and subsequent characterisation of numerous antigenic targets in these diseases, the development of antigen-specific tests, in particular, enzyme-linked immunosorbent assays on serum specimens, has provided a third key tool to not only identify, but also quantify AIBD autoantibodies. This quantification has proven particularly useful in monitoring disease activity and informing clinical management decisions. Accurate diagnosis of these diseases is important since optimal treatment strategies differ between them and, prognostically, some diagnoses are associated with an increased risk of malignancy. This review outlines the molecular pathology underlying the major AIBD and describes how the three principal techniques can be used in combination, to provide best practice for diagnosis and treatment monitoring.

Genetic diagnosis of a rare COL7A1 variant causing dystrophic epidermolysis bullosa pruriginosa through whole‑exome sequencing

Dystrophic epidermolysis bullosa pruriginosa (DEB-Pr) is a rare subtype of inherited DEB. In the present study, whole-exome sequencing was conducted on 12 individuals from the same affected family and a rare heterozygous variation was identified in the collagen type VII, α1 (COL7A1) gene, namely c.6859G>A (p.Gly2287Arg). Subsequently, this heterozygous variant was confirmed using Sanger sequencing of individual plasma cell-free DNA (cfDNA) and it was demonstrated for the first time, to the best of our knowledge, that COL7A1 exons can be amplified from plasma cfDNA. Within the large pedigree examined, 14 out of 18 individuals carried the variant, 3 carried the wild type, and one exceptional case, III-9, showed no disease symptoms despite carrying the disease variant. A general association between genotype and phenotype was established. Of note, the mutation landscape indicated that this G2287R variant is primarily reported in Asian countries. In silico structure prediction suggested that the residue resulting from the mutation may affect collagen protein stability. In conclusion, the present study provides evidence for the involvement of the COL7A1 G2287R gene variant in the development of DEB-Pr and highlights the potential utility of cfDNA in genetic disease diagnosis.

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.

[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.

[Immunopathogenesis of mucous membrane pemphigoid]

A detailed understanding of the immunopathogenesis of mucous membrane pemphigoid (MMP) is of particular importance in view of the mostly difficult diagnostics and treatment of this blistering autoimmune dermatosis. A still unknown disturbance of the body's own immune tolerance leads to the formation of autoreactive cells. As the disease progresses these produce autoantibodies which are directed against structural proteins in the basement membrane zone (BMZ). After they bind to the target antigen, complement factors are deposited along the BMZ and inflammatory cells invade the underlying tissue and produce the characteristic subepithelial blistering. This inflammatory response is associated with fibrosis and scarring in many affected tissues. Most phases of MMP pathogenesis are poorly understood; however, the last few years have shed more light on this processes. These advances are mostly the result of animal and cell culture models. Typical clinical and immunopathological characteristics of MMP, such as oral, conjunctival and skin lesions, are reflected, for example, in an antibody transfer-induced mouse model for anti-laminin 332 MMP in adult mice. Dapsone, as first-line treatment for MMP patients, significantly reduced the severity of these symptoms, and fibrosis in the skin and mucous membranes was also found histologically, which makes the model well-suited for testing new therapeutic approaches for MMP patients and might be of help for further elucidation of the immunopathogenesis of MMP.

Case report: Mucous membrane pemphigoid with complicated autoantibody profile indicating the necessity of comprehensive diagnostic methods and the contribution of IgA autoantibodies

Mucous membrane pemphigoid (MMP) is a type of subepithelial autoimmune bullous disease, affecting various mucosae, occasionally with skin lesions. Both diagnosis and treatment of MMP are difficult. Although multiple autoantigens have been identified for MMP, the pathogenesis of MMP is still unclear. In this study, we presented a female MMP case with extensive oral mucosal lesions and skin lesions, particularly on the extremities. IgG and IgA autoantibodies against multiple autoantigens including BP180, laminin 332, integrinα6β4 and desmoglein 3, and IgM autoantibodies against BP180 were identified during the disease course. Compared with IgG autoantibodies, the levels of IgA autoantibodies against various autoantigens decreased more significantly with improvement of clinical features after the initiation of treatments. Our findings indicated the importance of comprehensive autoantibody screening for different immunoglobulin types and autoantigens at multiple time points for the precise diagnosis of various autoimmune bullous diseases, and the significant involvement of IgA autoantibodies into the pathogenesis of MMP.