The Role of Anti-skin Antibodies Immunoglobulin G in the Diagnosis of Autoimmune Bullous Diseases

Background: Autoimmune bullous diseases (AIBDs) represent a group of acquired heterogenous organ-specific disorders in which pathogenic autoantibodies, commonly of IgG and/or IgA classes, target adhesion molecules of the skin and mucous membranes. These disorders are caused by the interaction between autoantibodies and structures essential for the integrity of the skin, either on keratinocytes cell surface or in the dermo-epidermal junction, leading to cleavage of the skin at different levels. Consequently, according to the level of cleavage, AIBDs are classified into intraepidermal and subepidermal blistering diseases. Diagnosis of AIBDs depends on the clinical, histological and immunological characteristics of each subtype. Immunofluorescence is pivotal for diagnosing AIBDs. Tissue-bound and/or circulating autoantibodies and the patterns of their binding to specific antigens can be demonstrated by direct and indirect immunofluorescence, respectively. Aim of the Work: To evaluate the performance characteristics of anti-skin antibodies IgG by indirect immunofluorescence (IIF) in the diagnosis of autoimmune bullous diseases. Subjects and Methods: Twenty-five patients with AIBDs including 14 pemphigus vulgaris (PV) patients, 5 pemphigus foliaceus (PF) patients and 6 bullous pemphigoid (BP) patients were studied, and compared with 10 patients with non-bullous skin diseases and 10 healthy subjects as controls. ASA-IgG were investigated by using IIF technique. Results: Positive anti-skin antibodies (ASA)-IgG IIF test was demonstrated in 92% of AIBD patients and in 20% of patients with non-bullous skin diseases. The test was negative in all ten healthy subjects. Thus, ASA-IgG were significantly positive in AIBDs than both non-bullous diseases patients and healthy control group. Two patterns of ASA-IgG binding to the corresponding antigens were seen; intercellular substance (ICS) pattern with serum samples from PV and PF patients that diagnose intraepidermal blistering diseases. Linear basement membrane zone (BMZ) pattern by serum samples obtained from BP patients that diagnose subepidermal blistering diseases. Conclusions: IIF assay is an accurate screening test for detection of circulating ASA-IgG that categorizes autoimmune bullous disorders into two major subtypes: pemphigus and pemphigoid based on antibody deposits staining patterns either ICS or linear BMZ pattern, respectively.