The renal pathology of primary antiphospholipid syndrome: a distinctive form of endothelial injury.

Some features of the vascular and glomerular pathology of primary antiphospholipid syndrome (APS) are well recognized, but we describe novel glomerular ultrastructural changes that we consider to be pathognomonic of APS. Renal biopsies from eight patients with APS were examined by light and electron microscopy. All had anti-cardiolipin antibodies, and the clinical presentation ranged from fulminant multi-system disease to isolated proteinuria. By light microscopy, the hexamine silver stain showed a combination of glomerular basement membrane wrinkling and reduplication. By electron microscopy, redundant, wrinkled segments of basement membrane were accompanied by a 'new' straighter thin basement membrane adjacent to the endothelium. In two cases the presence of these antibodies was not suspected clinically, and there was no clinical history or evidence of a thrombotic microangiopathy. We describe a distinctive glomerular lesion that represents an unexplained form of endothelial injury in this syndrome.