Lupus podocytopathy

Abstract

Systemic Lupus Erythematosus (SLE) is a systemic autoimmune disease which may affect several organs. Approximately 50% of SLE patients develop clinically overt renal disease, an important cause of morbidity and mortality. Nephrotic syndrome (NS) is frequent in patients suffering from lupus nephritis (LN) and it is usually associated with immune complex deposition on capillary walls accompanied by endocapillary proliferation and necrosis. However, a growing number of reported cases of SLE and NS patients show biopsies which reveal podocyte injury, consisting of pedicel fusion upon electron microscopy and a morphological pattern identical to minimal change disease (MCD), primary focal segmental glomerulosclerosis or mesangial proliferative glomerulonephritis, in absence of immune complex deposition on capillary walls. Although this finding could be explained by the coexistence of LN and MCD, most researchers consider that this fact is not pure coincidence. A new term, lupus podocytopathy, therefore appears to define a distinct entity characterized by T cell activation and the presence of a glomerular permeability factor. This allows to distinguish the group of SLE and NS patients whose biopsies do not show immune complex deposition on capillary walls or signs of renal lupus activity; electron microscopy reveals diffuse pedicel fusion and patients show high responsiveness to corticosteroid treatment. In order to diagnose this new entity, it is necessary to interpret histopathological findings together with data gathered from immunofluorescence and electron microscopy.