MPO and systemic lupus erythematosus: Systemic diseases (immunological or paraneoplastic) with suspected renal involvement [1,2]  e.g., clinical/serologic evidence of systemic vasculitis c/p-ANCA positive and PR3-/MPO-Abs positive [1,2,27]  e.g., clinical/serologic evidence of systemic lupus erythematosus (SLE) [1,2,30]  e.g., serologic evidence of monoclonal gammopathy [1]