The prognosis and pathogenesis of severe lupus glomerulonephritis

Background. The International Society of Nephrology/ Renal Pathology Society classification (ISN/RPS) of lupus glomerulonephritis (GN) divides diffuse GN (>= 50% involvement) into diffuse segmental (IV-S) and diffuse global GN (IV-G). This division tests whether the pathogenesis and clinical outcomes are the same as when similar patients are classified using the World Health Organization ( WHO) classification into severe segmental ( WHO III >= 50%) and diffuse global (WHO-IV) GN. Methods. Thirty-nine renal biopsies with WHO class IV and 44 with WHO III >= 50% were reclassified using the ISN/RPS and were correlated with pathogenesis and outcome. Results. There were 22 biopsies with ISN/RPS class IV-S. ISN/RPS class IV-G comprises two morphologically discrete classes of renal biopsies: 39 biopsies originally classified as WHO class IV (WHO-IV) and 22 that switched from WHO III >= 50% to ISN/RPS class IV-G (IV-Q). We will analyze IV-S, IV-Q and WHO-IV separately. WHO-IV had significantly more immune aggregate deposition than IV-S and IV-Q. WHO-IV had lower serum complements C3 ( P= 0.05) and C4 ( P = 0.05) than patients with IV-Q. Patients with WHO-IV had more remissions (56%) than IV-Q ( 23%) ( P= 0.01), and stable renal function at the last follow-up was less frequent in patients with IV-Q (18%) than IV-S ( 50%, P = 0.05) and WHO-IV (62%, P= 0.001). Renal survival and renal survival without end-stage renal disease were different when the patients were diagnosed as WHO classes III = 50% and IV, but the outcomes for ISN/RPS class IV-S and IV-G (WHO-IV plus IV-Q) were not different. Conclusions. WHO III = 50% and WHO-IV lupus GN are not congruent with ISN/RPS IV-S and IV-G. The ISN/RPS minimizes pathological and outcome differences between classes IV-S and IV-G which results in the loss of informational content from the renal biopsies. ISN/RPS does not detect pathogenetic or clinical differences among patients with severe lupus GN.