Renal Vascular Complications of Systemic Lupus Erythematosus1
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Renal Vascular Complications of Systemic Lupus Erythematosus1 Gerald B. Appel,2 Conrad 1. Pirani, and Vivette D’Agati out that, with the exception of cutaneous vasculitis, GB. Appel, CL. Pirani, V. D’Agatl, Departments of true inflammatory lesions of larger arteries are rela- Medicine and Pathology, Columbia-Presbyterian tively uncommon in SLE (3,14,15). Medical Center, New York, NY In our own experience and that of others (15-22), the pathology of the renal vasculopathies seen in SLE (J. Am. Soc. Nephrol. 1994: 4:1499-1515) patients may take several morphologically distinct forms: uncomplicated vascular Immune deposits, noninflammatory necrotizing vasculopathy, throm- enal vascular complications are not infre- botic microangiopathy, and true vasculitis of the mi- quently encountered in systemic lupus cry- croscopic polyarteritis nodosa (PAN) type. thematosus (SLE), and their occurrence can have a profound effect on the clinical course and choice of Vascular Immune Complex Deposits therapy. A variety of histopathologic lesions of the The most common renal vascular lesion in SLE is renal vessels as well as a number of distinct clinical immune complex deposition in the walls of arterioles, syndromes related to vascular damage may occur In SLE. These renal vasculopathies include vascular small arteries, and to a far lesser extent, veins (19,21,23,24). By light microscopy (LM), the vessels Immune complex deposition, noninflammatory nec- rotizing vasculopathy, thrombotic microangiopathy, usually appear normal. Less commonly, eosinophilic, and true renal vasculitis. The clinical syndromes of periodic acid-Schiff-positive, and fuchsinophilic de- thrombotic thrombocytopenic purpura (TTP), anti- posits are seen beneath the endothelium or between cardiolipin syndrome, and renal vein thrombosis the cells of the media (19). No thrombosis, necrosis, (RVT) are also well-documented vascular coinplica- or inflammatory infiltration of the vessel wall is pres- tions of SLE. Because glomerular pathology is of ent, and the lumen is usually not compromised (Fig- primary importance in the classification of lupus ure 1). By immunofluorescence microscopy (IF), the nephritis, the presence and significance of these vas- deposits may contain immunoglobulin G (IgG), 1gM, cular lesions are often overlooked. Although the path- IgA, and complement components (FIgure 2). By dcc- ogenesis of many of these vascular entities is not fully defined, therapeutic intervention has often been successful. This article reviews their pathology, pathogenesis, epidemiology, and clinical course, as well as the various therapeutic strategies used to treat the vascular complications of SLE. HISTOPATHOLOGY AND PATHOGENESIS OF LUPUS RENAL ARTERIOPATHIES In the past, the term “lupus vasculitis” was used Indiscriminately and included a variety of arterial lesions involving not only the renal circulation but also the vessels of the upper and lower extremities and the coronary, mesenteric, gallbladder, and cere- bral circulations (1-14). Recent studies have pointed Figure 1. Vascular Immune deposits thicken the subendo- Received September 3, 1992. Accepted October 10, 1993. theliai basement membranes of multiple small interlobuiar 2coffe$pondeflce to Dr. G.B. Appel, Department of Medicine, columbia- arteries. The lumen is not significantly narrowed. There is no Presbyterian Medical center. New York, NY 10032-3784. associated inflammation, necrosis, or thrombosis. Uncom- 1046-6673/0408-1499$03.00/0 Journal of the American Society of Nephroiogy plicated vascular immune deposits. Periodic acid-Schiff, copyright C 1994 by the American Society of Nephroiogy x320. Journal of the American Society of Nephrology 1499 Renal Vascular Complications of SLE cular (adventitial) deposits present. Such vascular deposits are more commonly found with active gb- merular proliferative forms of lupus nephritis (World Health Organization (WHOI Classes III and IV), typi- cabby in association with tububointerstitial deposits. However, they can also be seen in some cases of mesangial proliferative (Class II) and membranous (Class V) lupus nephritis. They may be overlooked in biopsies because they are often not apparent by LM, because they are focally distributed, and because greater attention is usually directed to the gbomerular pathology. Histologically identifiable vascular depos- its may be more common in autopsy specimens, par- ticularly from the presteroid era (19). The pathogenic mechanisms underlying this type Figure 2. By IF, deposits of 196 are detected in the walls of of vascular lesion are probably the same as those several small arteries. Same biopsy as that shown in Figure that mediate gbomerular and tububointerstitial im- 1. Uncomplicated vascular Immune deposits. IF, x400. mune deposit formation. The vascular deposition of circulating immune complexes is a probable mecha- tron microscopy (EM), the deposits are electron dense nism, given the frequency of this vascular lesion in and discrete and often have a granular texture, al- patients with the proliferative forms of lupus gbomer- though occasionally a fingerprint or tactoid substruc- ulonephritis. It is not known whether the in situ ture is seen (Figures 3-5). They are most commonly formation of immune deposits may also play a role. located beneath an intact vascular endothelium or Uncomplicated immune deposits in the wall of small within the basement membranes surrounding the renal arteries may be considered analogous to the medial myocytes (Figure 6). Only rarely are perivas- gbomerular Immune deposits seen in lupus nephritIs FIgure 3. The same biopsy as that shown in Figures 1 and 2 reveals multiple coarsely granular, electron-dense deposits within the subendotheiIal basement membrane of small arteries. A tubuloreticular inclusion (arrow) is present in the endotheiium. LU, lumen. Uncomplicated vascular immune deposits. Electron micrograph, x#{243},000. 1500 Volume 4 Number 8’ 1994 Appel ef al microscopy will help in differentiating hyalinosis from vascular deposits of immune complexes. Differ- entiation is more difficult when the two diseases are present together. Noninflammatory NeCrotizing VasCulopathy This type of vasculopathy is much less common than simple vascular immune deposits and may rep- resent a complication of more severe forms of im- mune complex deposition. It predominantly affects preglomerular arterioles and to a lesser extent the interbobular arteries, frequently in the setting of ac- five, diffuse proliferative lupus gbomerubonephritis. This lesion is characterized by necrotizing changes in the vessel wall associated with abundant immune complex deposits, causing significant luminal nar- rowing or occlusion (16-20,25,26). By LM, smudgy eosinophilic, fuchsinophilic material that stains fo- cally positive for fibrin occupies the lumen and in- Figure 4. Mauive confluent electron-dense deposits in the intima and media of an arteriole. Uncomplicated vascular tima, with frequent extension into the media. The immune deposits. Electron mlcrograph, x4,500. endothelium is usually swollen or denuded, with oc- casional pyknotic nuclear fragments and smudgy de- generation of the medial myocytes (Figure 7). The elastic membrane of the interlobular arteries is usu- ally disrupted. Rarely, a few lymphocytes may be seen in the lumen or intima (1 6, 1 9). By IF, variable staining for IgG, 1gM, IgA, complement components, and fibrin-related antigens is present in the wall and extends to the lumen, (1 6, 1 9,26) (Figure 8). Ultra- structurally, there is swelling or loss of endothelium, with massive confluent intraluminal and mural de- posits of granular electron-dense material, with the combined appearance of insudated proteins, and im- mune deposits, sometimes associated with tactoids of fibrillar fibrin and platelets. Degenerative changes may be seen in the medial myocytes adjacent to these deposits (16). The pathogenesis of this noninflammatory necro- tizing vascubopathy is uncertain. Its occurrence In patients with mild or no hypertension, the infrequent presence of hypertensive retinopathy, and the histo- pathologic findings of vascular immune deposits in Figure 5. Electron-dense deposit with organized substruc- addition to fibrin all militate against malignant hy- ture in the media of a small artery. Uncomplicated vascular pertension as the primary etiologic process. However, immune deposits. Electron micrograph, x15,000. it is likely that the superimposition of severe hyper- tension may exacerbate these vascular lesions Class ha, where mesangial deposits do not incite (19,26). The presence of abundant electron-dense gbomerular cell proliferation (20). vascular deposits consisting in part of immunoglob- This type of lupus vasculopathy must be differen- ulins and complement strongly suggests immuno- tiated from hyalinosis, a lesion frequently associated logic factors in the evolution of these lesions (18,26). with hypertension and the arteriobosclerosis that Secondary thrombosis might contribute to the dam- commonly accompanies the more chronic, inactive age occurring in those vessels (16,17,19). The fact forms of lupus nephritis. The associated findings of that such vascular lesions are most common in pa- intimal and medial sclerosis involving the arterioles tients with active proliferative lupus gbomerubone- and the small arteries and the presence of 1gM and phritis also supports a role for immune deposition as C3 only (but not of IgG and IgA) by fluorescence a primary process (16-19,26). The possible involve- Journal of