The Intrarenal Vascular Lesions Associated with Primary Antiphospholipid Syndrome

Even 10 yr after the identification of the antiphospholipid syndrome (APS), renal involvement in the course of APS is still relatively unrecognized, and is probably underestimated. The association of anticardiolipin antibodies and/or lupus anticoagulant with the development of a vaso-occlusive process involving numerous organs is now confirmed. In a multicenter study, 16 cases of "primary" APS (PAPS) were found and followed for 5 yr or more, all with renal biopsy. In all 16 cases of PAPS, there was a vascular nephropathy characterized by small vessel vaso-occlusive lesions associated with fibrous intimal hyperplasia of interlobular arteries (12 patients), recanalizing thrombi in arteries and arterioles (six patients), and focal cortical atrophy (10 patients). In combination, these led to progressive destruction of the kidney, accelerated by acute glomerular and arteriolar microangiopathy in five patients. Focal cortical atrophy is a distinctive lesion, present in 10 biopsies, and likely represents the histologic and functional renal analogue to the multiple cerebral infarcts detected on imaging studies. The clinical hallmark of this vascular nephropathy in PAPS is systemic hypertension, only variably associated with renal insufficiency, proteinuria, or hematuria. The ensemble of histologic renal lesions defined in this study should aid in the separation of the lesions found in cases of secondary APS, especially systemic lupus erythematosus, into those lesions related to APS and those related to the underlying disease.