MPO ANCA Positivity in IgA Nephropathy: Imposter or Implication?

Background: IgA nephropathy is the most common primary glomerulonephritis, while the most common cause of rapidly progressive glomerulonephritis (RPGN) is pauci immune crescentic glomerulonephritis (GN), followed by Immune complex mediated GN and anti Glomerular basement membrane (GBM) disease. Anti neutrophil cytoplasmic autoantibody (ANCA) is characterised by crescentic necrotizing GN on renal biopsy with minimal deposits. Immunoglobulin A (IgA) nephropathy may present as crescentic GN with mesangial IgA deposits and sometimes around capillary as well. The co existence of circulating ANCA in a patient of IgA nephropathy with RPGN presentation is a rare phenomenon and very less literature is available for the same.

Case Presentation: This case describes a rare presentation of RPGN which was myeloperoxidase (MPO) positive on enzyme immunoassay (EIA) with central nervous system (CNS) vasculitis presenting as hemiparesis. Patient was treated as ANCA vasculitis, with plasmapheresis (PLEX) and Cyclophosphamide as Standard of care as KDIGO suggests treatment may be initiated without biopsy when presence of RPGN picture with circulating ANCA. However, renal biopsy, later revealed features of crescentic IgA nephropathy but the presence of systemic symptoms makes IgA nephropathy as the sole diagnosis highly unlikely, hence a possibility of MPO IgA concurrence remains high. Hence our case was treated in the lines of ANCA vasculitis with IV cyclophosphamide according to EUVAS protocol. Our case is at sustained remission at 6 months after 10 doses of cyclophosphamide as SOC and has now been shifted to maintenance therapy on Azathioprine (Aza), given the possibility of relapse.

Conclusion: Hence MPO ANCA vasculitis and IgA nephropathy is a very rare concurrence. The presence of CNS vasculitis in this background is never reported. However, this case drastically improved with Pulse cyclophosphamide and corticosteroids.