MPO and kidney disorder: He underwent examinations for differential diagnosis from other kidney diseases: immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin M (IgM), C3, C4, cryoglobulin, proteinase 3-antineutrophil cytoplasmic antibody (PR3-ANCA), and myeloperoxidase-antineutrophil cytoplasmic antibody (MPO-ANCA).