A Concomitant Case Of Pathologically Proven Igg4-Related Disease And Anca-Associated Vasculitis: Case Report

A 63-year-old male visited our hospital after bilateral apical lung masses were detected on medical check-up chest X-ray. Histopathology of the resected mass revealed storiform fibrosis with an increased number of immunoglobulin G4 (IgG4)-positive plasma cells, compatible with IgG4-related disease (IgG4-RD). The patient was subsequently followed up without treatment for 3 years. Later, at age 66, he revisited our hospital because of scleritis, proteinuria, and myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA) positivity (179 U/ml). A renal biopsy revealed pauci-immune necrotising crescentic glomerulonephritis. After high-dose prednisolone (PSL) was started, the patient's scleritis subsided and his MPO-ANCA level and proteinuria were decreased. Subclass-based indirect immunofluorescence revealed that the patient's serum was positive for IgG1-type ANCA but negative for IgG4-type ANCA. Including the present case, there have been nine reported cases involving both biopsy-proven IgG4-RD and ANCA-associated vasculitis (AAV). In all these concomitant cases of IgG4-RD and AAV, PSL and immunosuppressants were used to control AAV. Deliberate care should be taken to distinguish between IgG4-RD and AAV at diagnosis as they have overlapping features and can, though very rarely, occur concomitantly.