Mucous membrane pemphigoid encompasses a group of autoimmune bullous diseases with a similar phenotype characterized by subepithelial blisters, erosions, and scarring of mucous membranes, skin, or both. Although knowledge about autoimmune bullous disease is increasing, there is often a lack of clear definitions of disease, outcome measures, and therapeutic end points. With clearer definitions and outcome measures, it is possible to directly compare the results and data from various studies using meta-analyses. This consensus statement provides accurate and reproducible definitions for disease extent, activity, outcome measures, end points, and therapeutic response for mucous membrane pemphigoid and proposes a disease extent score, the Mucous Membrane Pemphigoid Disease Area Index.

Bullous pemphigoid (BP) is a sub-epidermal autoimmune blistering disease associated with autoantibodies to the dermal–epidermal junction (DEJ). Patients’ autoantibodies induce dermal–epidermal separation when co-incubated with cryosections of human skin and leucocytes from healthy volunteers. IgG autoantibodies trigger complement and/or leucocyte activation resulting in specific pathology in several autoimmune conditions. In these diseases, IgG1 and IgG3 isotypes, but not the IgG4 subclass, are thought to trigger inflammatory pathways resulting in tissue damage. The capacity of IgG4 autoantibodies to mediate tissue damage has not yet been demonstrated. In this study, we isolated IgG1 and IgG4 autoantibodies from bullous pemhigoid patients'serum and analysed their blister-inducing potential in our cryosection assay. As expected, complement-fixing IgG1 autoantibodies induced sub-epidermal splits in this experimental model. Purified IgG4 did not fix complement, but, interestingly, like IgG1, activated leucocytes and induced dermal–epidermal separation. The potential of IgG4 autoantibodies to induce Fc-dependent dermal–epidermal separation was significantly lower compared to IgG1. Our results demonstrate that IgG4 autoantibodies are able to activate leucocytes and point to a hitherto less recognized function of IgG4. Moreover, for the first time, we clearly demonstrate that BP IgG4 autoantibodies have the capacity to induce leucocyte-dependent tissue damage.

Patients with DPP-4 inhibitor-induced BP may present either an inflammatory or a noninflammatory phenotype of BP. IgG response against other BP180 regions different from the NC16A domain, such as LAD-1 and the C-terminal domain, could be pathogenically relevant to the onset of DPP-4 inhibitor-induced BP.

Background: Lichen planus is a common inflammatory autoimmune condition of unknown etiology that commonly affects the skin and mucous membranes. Isolated ocular lichen planus is an extremely rare presentation that most commonly involves the eyelids, conjunctiva, and cornea, leading to severe scarring, and is clinically indistinguishable from other causes of cicatricial conjunctivitis.Observations: A 79-year-old man complained of a chronic keratoconjunctivitis refractory to multiple topical treatments. Slit-lamp examination revealed diffuse bilateral conjunctival hyperemia, subepithelial fibrosis, and symblepharon, with a marked shortening of the lower conjunctival fornix. There were no other skin or mucosal lesions. Hematoxylin-eosin staining revealed acanthosis, focal thickening of the basement membrane, and a dense subepithelial mononuclear infiltrate. Direct im-