The clinico-pathological features of lupus nephritis and the significance of ISN/RPS-2003 Class IV lesions

Background: The ISN/RPS-2003 classification of lupus nephritis should emphasize clinically relevant lesions and encourage uniformity and reproducibility in histopathological reporting. Objective: To describe the clinico-pathological features of lupus nephritis and discuss the significance of the ISN/RPS-2003 class IV-G and IV-S lesions. Method: The histopathological features and corresponding clinical data of 75 patients with lupus nephritis were analysed using the International Society of Nephrology/Renal Pathology Society ISN/RPS - 2003 classification. This was a retrospective descriptive study carried out over a period of two and a half years at the Department of Pathology, Faculty of Medicine, Colombo. Results and conclusions: Lupus nephritis was commoner in females (88%, 66/75), with 52%, (36/75) in the 21-30 year age group. ANA positivity (93%, 70/75) was the commonest ACR (American College of Rheumatology - 1997) criterion to clinically diagnose SLE. Asymptomatic sub-nephrotic proteinuria was found in 47% (35/75), nephrotic syndrome in 21% (16/75) and hypertension in 17% ( 13/75). Endocapillary proliferation 84% (63/75) and wire-loop lesions 51% (38/75) were found to be the commonest histological features. 79% (59/75) had ISN/RPS class IV lupus nephritis (diffuse lupus nephritis) with the majority 93% (55/75) belonging to class IV-G (predominantly diffuse global lesions) and the remainder to class IV-S (predominantly segmental lesions). The pathogenesis of class IV-G lesions is thought to be immune complex mediated where as class 1V-S lesions are thought to show injury analogous to systemic vasculitides, unrelated to immunologic injury. Data on the prognostic outcomes of the two groups is conflicting because class IV-G is morphologically heterogenous, with two prognostically and pathogenetically distinct subcategories. Journal of Diagnostic Pathology 2014; 9(2): 14-22