Diagnostic features of pemphigus vulgaris in patients with bullous pemphigoid. Molecular analysis of autoantibody profile

BACKGROUND: The simultaneous presence of features of pemphigus vulgaris (PV) in patients with bullous pemphigoid (BP) has previously been reported in the literature. OBJECTIVE: The purpose of this retrospective study is to present 13 patients with an initial diagnosis of BP, who subsequently demonstrated coexistent serological features of both BP and PV. METHODS: The following information on each patient was documented, at the time of initial diagnosis: clinical profile on presentation, histology, direct immunofluorescence, indirect immunofluorescence (IIF) using monkey esophagus as substrate, salt-split skin (SSS) and an immunoblot assay. Since all 13 patients failed to respond to conventional systemic therapy, intravenous immunoglobulin (IVIg) was used as an alternative treatment modality. Prior to initiating IVIg therapy, in all 13 patients, serological studies were performed. In addition to IIF using monkey esophagus, an immunoblot assay and SSS, an enzyme-linked immunosorbent assay (ELISA) was performed to detect antibodies to desmogleins. These different assays were done to identify pathological autoantibodies typical of BP and PV. A control group of 25 healthy normal individuals, 37 patients with BP, 17 patients with PV and 12 patients with pemphigus foliaceus were used for comparison of serological studies. RESULTS: At the time of initial presentation, histological and immunopathological studies confirmed the diagnosis of BP in all 13 patients. Prior to the initiation of IVIg therapy, results of IIF using monkey esophagus as substrate demonstrated high levels of anti-intercellular cement substance (anti-ICS) or antikeratinocyte cell surface antibody. Sera of all 13 patients on SSS bound to the epidermal side of the split. In an immunoblot, using bovine gingival lysate as substrate, sera of 6 patients bound to both a 230-kD (BP Ag1) and 180-kD protein (BP Ag2), while 7 sera bound to only a 230-kD protein. All 13 patients had high levels of antibodies to desmoglein 3 on ELISA. In a pilot experiment, the anti-ICS antibody in sera from 6 random patients was found to be predominantly of the IgG4 subclass. Use of IVIg resulted in an effective clinical response and the maintenance of a prolonged clinical remission. CONCLUSION: In patients with BP, who are nonresponsive to conventional therapy, the presence of two autoimmune diseases or a dual diagnosis should be considered.