Antiphospholipid syndrome (APS) and the renal involvement

APS renal involvement was probably underestimated and not well characterized until recently. A possible explanation is that several manifestations of renal involvement (hypertension, hematuria, and proteinuria) were often neglected and that renal biopsy was rarely performed due to the frequent occurrence of thrombocytopenia and the use of anticoagulants among APS patients. The true prevalence of renal involvement in APS is difficult to establish; in the few retrospective studies on large cohorts of APS patients, it is reported of 9–10 % but it is probably higher. Renal involvement in APS is characterized by noninflammatory occlusion/thromboses of renal vessels (arterial and venous) ranging in size from large vessels to intrarenal microvasculature. In addition to vaso-occlusive abnormalities, other kinds of renal lesions such as glomerulonephritis have been reported in primary APS (PAPS). This heterogeneity of renal involvement could be explained by the presence of different underlying pathogenetic mechanisms. From a clinical point of view, the most frequent signs and laboratory characteristics of APS renal involvement include hypertension, hematuria, acute renal failure, and progressive chronic renal insufficiency with mild to nephrotic range proteinuria. APS can also cause end-stage renal disease (rare) and allograft vascular thrombosis. This chapter reviews the range of renal abnormalities associated with APS, their diagnosis, and treatment options.