Myeloperoxidase ‐antineutrophil cytoplasmic antibody causes different renal diseases by immune‐complex formation and pauci‐immune mechanism: A case report

Antineutrophil cytoplasmic antibody (ANCA) has been known to cause pauci‐immune crescentic glomerulonephritis. In addition, several reports described membranous glomerulonephritis (MN) concurrent with ANCA‐associated glomerulonephritis. Because the two glomerular diseases simultaneously appear in an ANCA‐positive patient, the mechanisms whereby ANCA causes the two different glomerular diseases remain ambiguous. Herein, we report a case of 19‐year‐old man who presented with hematuria, pre‐nephrotic proteinuria, and high titer of myeloperoxidase (MPO)‐ANCA. The first renal biopsy revealed MN with chronic glomerular scar lesions of unknown etiology. Predominant immunoglobulin (Ig) G1 subclass and negative phospholipase‐A2 receptor staining, together with granular‐positive glomerular capillary co‐localization of MPO and IgG staining, suggested secondary MN due to MPO‐MPO‐ANCA immune‐complex. Five years later, the patient presented with fever, severe renal dysfunction, and alveolar hemorrhage with high titer of MPO‐ANCA that indicated pulmonary renal syndrome due to ANCA‐associated vasculitis. The second renal biopsy revealed pauci‐immune crescentic glomerulonephritis without either apparent MN‐lesion or glomerular IgG staining. This is the first reported case showing that MPO‐ANCA caused two different glomerular diseases, MN and pauci‐immune crescentic glomerulonephritis, in the same patient at the different time points. Our case indicated th...
Source: Pathology International - Category: Pathology Authors: Tags: Case Report Source Type: research