High anti–desmoglein 3 antibody ELISA index and negative indirect immunofluorescence result in a patient with pemphigus vulgaris in remission: evaluation of the antibody profile by newly developed methods.

IMPORTANCE Pemphigus vulgaris (PV) is a disease that features blistering of the skin and mucous membranes caused by autoantibodies directed against desmoglein 3 (Dsg3) and/or desmoglein 1(Dsg1). Indirect immunofluorescence (IIF) and enzyme-linked immunosorbent assay (ELISA) are 2 methods that are widely used to measure Dsg3 orDsg1 antibody titers in PV. Although the titers of these autoantibodies are generally correlated with disease activity, some patients with a high ELISA index do not have severe symptoms.We encountered a patient with PV in remission,who had a high anti-Dsg3 antibody ELISA index while the IIF result was negative.OBSERVATIONS The anti-Dsg3 antibodies of our patient mainly recognized Ca2+-dependent conformational epitopes and targeted mature Dsg3 protein.We report this case focusing on the discrepancy between ELISA and IIF findings, as well as on the specific characteristics of the patient's autoantibodies evaluated by newly developed methods.CONCLUSIONS AND RELEVANCE This case emphasizes that a discrepancy between disease activity, the ELISA index for Dsg3, and/or IIF findings can occur in PV. Further research on similar patients will be required to elucidate the pathogenic mechanisms in patients with PV who have nonpathogenic antibodies and show a discrepancy between ELISA and IIF.