Antineutrophil cytoplasmic antibody and/or antiglomerular basement membrane antibody associated crescentic glomerulonephritis in combination with IgG4-related tubulointerstitial nephritis

Immunoglobulin G4 (IgG4)-related disease (IgG4-RD) is an immune-mediated fibroinflammatory disorder and is characterised by elevated serum IgG4 concentrations and dense lymphoplasmacytic infiltrate rich in IgG4+ plasma cells. IgG4-related tubulointerstitial nephritis (IgG4-TIN) is the most common manifestation of IgG4-related kidney disease (IgG4-RKD). We report four cases of kidney injury with concurrent IgG4-TIN and crescentic glomerulonephritis confirmed by renal pathology. The medical charts of four patients were reviewed to collect clinical and laboratory data at the time of diagnosis, treatment and outcomes after 6-36 months. Two of them are cases of IgG4-TIN with antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), and the other two cases are rare IgG4-TIN with antiglomerular basement membrane (anti-GBM) glomerulonephritis coexistent with ANCA-positive serum. Compared with IgG4-TIN, IgG4-TIN combined with AAV or anti-GBM glomerulonephritis is less associated with other organ injuries, and the clinical manifestations, treatment effects and prognosis were consistent with that of crescentic glomerulonephritis. IgG4-TIN concurrent with anti-GBM glomerulonephritis and positivity in serum has more severe clinical features and a worse renal prognosis than IgG4-TIN coexistent with AVV.