Do ANCA-associated vasculitides and IgG4-related disease really overlap or not?

Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) and immunoglobulin G4-related disease (IgG4-RD) have some common features. The co-occurrence/concurrence of AAV and IgG4-RD was recently published by the collaborative European Vasculitis Study Group. First, we aimed to investigate ANCA positivity of our IgG4-RD cohort. Second, a literature review of co-occurrence/concurrence of AAV and IgG4-RD was done.

Data of 62 patients with IgG4-RD in Hacettepe Vasculitis Center Database were used. Patient dataset was designed to include demographic data, clinical characteristics, imaging and IgG4-RD, AAV and ANCA test results. At the next step, we performed a systematic literature review in PUBMED database covering the time period from 1976 until April 2018. Relevant publications were searched using these MeSH terms ''IgG4-related disease and Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis'', "IgG4-related disease and Eosinophilic Granulomatosis with Polyangiitis", "IgG4-related disease and Microscopic Polyangiitis" and "IgG4-related disease and Granulomatosis with Polyangiitis".

Three (10.3%) of 29 patients had low titer ANCA positivity. These three patients didn't have any findings of vasculitis and no granuloma was seen in biopsy. In the literature review, we found 17 cases had features of both IgG4-RD and AAV. These cases were re-evaluated according to the Comprehensive Diagnostic Criteria for IgG4-RD. ANCA were positive in 15 of 17 patients (88%).

None of our IgG4-RD patients overlapped with AAV. Only two patients in the literature review seemed to be fully compatible with both diseases. Even though AAV and IgG4-RD share similar clinical features, we think this might be a co-occurrence instead of a histopathological link.