Place of human amniotic membrane immunoblotting in the diagnosis of autoimmune bullous dermatoses

Background Fine analysis of antiskin autoantibodies can contribute to the differential diagnosis of autoimmune bullous dermatoses. Objectives To develop a high‐performance immunoblotting method using human amniotic membrane as the antigen source, and to compare it with current laboratory methods. Methods Sera from 113 patients were tested by immunoblotting (IB), rat and monkey oesophagus and salt‐split skin indirect immunofluorescence (IIF), and enzyme‐linked immunosorbent assay (ELISA) quantification of anti‐BP180‐NC16a and anti‐BP230, or antidesmoglein (Dsg) 1 and 3 antibodies. There were 56 cases of bullous pemphigoid (BP), 22 cases of mucous membrane pemphigoid (MMP), eight cases of epidermolysis bullosa acquisita (EBA), two cases of bullous systemic lupus erythematosus (BSLE), 17 cases of pemphigus vulgaris (PV), and four cases each of pemphigus foliaceus (PF) and paraneoplastic pemphigus (PNP). Results In BP, the three methods had similar sensitivity (84–89%) for both anti‐BP180‐NC16a and anti‐BP230 antibody detection. In MMP, autoantibodies (mainly directed against BP180 or laminin 332 subunits) were detected in 77% of patients by IB, compared with only 9% by IIF on rat and monkey oesophagus and 36% on salt‐split skin, and 14% by anti‐BP180‐NC16a and anti‐BP230 ELISA. In patients with pemphigus, ELISA had 92% sensitivity for anti‐Dsg1 and 3, but IB and rat bladder IIF were necessary to confirm PNP by revealing specific and rare patterns (antidesmoplakin I/II, antienvoplakin and antiperiplakin antibodies). IB also revealed anticollagen VII antibodies in 60% of patients with EBA and BSLE, and antibodies to BP180, BP230 and Dsg3 in a few patients who were negative using the other two techniques. Conclusion Amniotic membrane immunoblotting is an interesting diagnostic tool for bullous diseases, as the entire panel of autoantibodies can be detected with a single extract. This method improves the identification of complex and heterogeneous autoimmune processes in conjunction with IIF and ELISA, and is particularly useful for MMP characterization.