Isolated renal involvement in IgG4related disease presenting with dual ANCA positivity

IgG4-related disease (IgG4-RD) is a rare fibroinflammatory disorder that can affect almost any organ and is characterized by a lymphoplasmacytoid infiltrate, obliterative phlebitis, and storiform fibrosis. It is often associated with eosinophilia and elevated serum IgG4 levels. Isolated renal involvement is relatively uncommon. Several other conditions may mimic IgG4-RD clinically and radiologically, for example antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis, lupus nephritis, lymphoma, inflammatory pseudotumor, drug-induced tubulointerstitial nephritis (TIN), Sjogren syndrome-associated tubulointerstitial nephritis, and sarcoidosis. We present a case of 55-year male who presented with complaints of bilateral lower limb swelling and frothing of urine. Laboratory investigations revealed elevated serum creatinine, subnephrotic proteinuria, and bland sediments. ANCA were elevated. Renal biopsy showed lymphoplasmacytic infiltrate, with storiform fibrosis and raised IgG4-positive plasma cells, fulfilling the criteria for IgG4-related tubulointerstitial nephritis. Later serum IgG and IgG4 levels also came out also elevated. However, the presence of ANCA was a confounding factor in the present case. The patient was initiated on steroid therapy. Patients with biopsy-proven IgG4-RD may have positive ANCA with specificity for myeloperoxidase or proteinase-3, with or without an overt ANCA-associated vasculitis (AAV). Thus, the presence of concurrent ANCA autoantibodies has no clinical implication unless accompanied by clinical and histological features of AAV.