Serum and salivary IgG and IgA antibodies to desmoglein 3 in mucosal pemphigus vulgaris

Summary Background The use of saliva for the diagnosis of pemphigus vulgaris (PV) by enzyme‐linked immunosorbent assay (ELISA) using desmoglein (Dsg)3 antigen has not been extensively documented, nor has the detection of serum IgA antibodies to Dsg3. Objectives (i) To establish whether whole saliva might provide a suitable alternative to serum for diagnosing and monitoring PV; (ii) to investigate whether anti‐Dsg3 IgA antibodies can be detected in serum and saliva and (iii) to establish whether there is an association between serum or saliva anti‐Dsg3 antibodies and disease severity. Methods Precoated Dsg3 ELISA plates were used to test serum and/or saliva for IgG and IgA antibodies. Matched serum and whole saliva samples were collected from 23 patients with PV, 17 healthy subjects and 19 disease controls. All patients with PV, disease controls and six healthy controls provided matched parotid saliva. Results Whole saliva IgG antibodies to Dsg3 were detected in 14 of 23 patients (61%) and serum IgG antibodies were detected in 17 of 23 (74%) with a strong positive correlation. Serum IgA antibodies were detected in 14 of 23 patients with PV (61%) with a combined positivity (IgG and/or IgA antibodies to Dsg3) of 78% (18 of 23). We were unable to show IgA anti‐Dsg3 antibodies in either whole or parotid saliva of patients with PV. Sequential samples showed that changes in IgG antibody titres in whole saliva were associated with a change in disease severity scores. Conclusions Assay of salivary IgG antibodies to Dsg3 offers a diagnostic alternative to serum in the diagnosis and monitoring of PV. The role of anti‐Dsg3 IgA antibodies requires further elucidation in the pathogenesis of PV. What's already known about this topic? The use of serum to test for IgG autoantibodies to desmoglein (Dsg)3 by enzyme‐linked immunosorbent assay has been well documented. Salivary IgG anti‐Dsg3 antibodies have been previously detected in three studies in pemphigus vulgaris (PV) and have been proposed as a diagnostic marker. What does this study add? This study demonstrates that detection of salivary antibodies provides a practical alternative to serum in the diagnosis of PV. Salivary antibodies may also be used for the monitoring of disease activity in patients with PV. Both IgG and IgA serum antibodies to Dsg3 are detected in IgG‐driven PV. Further investigation is needed to understand the role of IgA in the pathogenesis of PV. What is the translational message? The simplicity o