PLA2R1 and vasculitis: However, specific circulating biomarkers of disease are available for only a small subset of pathologies, for example, the presence of anti‐phospholipase A2 receptor (PLA2R) antibodies in membranous nephropathy 1, the presence of anti‐myeloperoxidase (MPO) or anti‐proteinase 3 (PR3) antibodies in anti‐neutrophil cytoplasmic antibody (ANCA)‐associated vasculitis, or circulating anti‐glomerular basement membrane (GBM) antibodies in Goodpasture's disease 1, 2.