Detection of linear IgE deposits in bullous pemphigoid and mucous membrane pemphigoid: a useful clue for diagnosis

Summary Background Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease of the skin associated with IgG autoantibodies to BP180 and BP230, while mucous membrane pemphigoid (MMP) comprises a heterogeneous group of autoimmune blistering diseases characterized by a predominant mucous membrane involvement and scarring tendency associated with an autoantibody response to various autoantigens, including BP180. While the pathogenicity of IgG autoantibodies to BP180 has been demonstrated in BP, the role of IgE autoantibodies in mediating tissue damage in BP and MMP is unclear. Objectives To assess the presence of tissue‐bound IgE in patients with BP and MMP, and their correlation with distinct clinical features. Methods In this retrospective study, we assessed the presence of IgE deposits as detected by direct immunofluorescence microscopy of skin biopsy specimens obtained from 44 and 13 patients with a new diagnosis of BP and MMP, respectively. Distinct clinical features at time of diagnosis, such as itch, urticarial papules and plaques and eczematous lesions, were noted. Results In 18 of 44 (41%) patients with BP linear deposits of IgE of variable intensity were detectable along the dermoepidermal junction. In 14 (32%) of the cases, IgE deposits were found concomitantly with IgG and C3. In two (5%) patients, diagnosis of BP was based on the isolated detection of IgE together with consistent clinicopathological features. Nine of 13 (69%) patients with MMP also exhibited linear IgE deposits, including one case with isolated linear IgE deposits. Patients with BP with tissue‐bound IgE deposits had clinically significant urticarial papules and plaques when compared with patients with BP without IgE deposits. Conclusions Our findings indicate that demonstration of tissue‐bound IgE deposits provides an additional useful criterion for diagnosis of BP and MMP in some patients. Prospective studies are needed to better correlate the presence of tissue‐bound and circulating IgE autoantibodies and their specificity with distinct clinical features and course of BP and MMP.