Pathologic differentiation between lupus and nonlupus membranous glomerulopathy

Pathologic differentiation between lupus and nonlupus membranous glomerulopathy. The following clinical and pathologic features were evaluated in 170 patients with electron microscopically documented membranous glomerulopathy: age, sex, race, American Rheumatism Association lupus criteria, serum ANA, serum complement, glomerular hypercellularity, stage of subepithelial dense deposits, endothelial tubuloreticular inclusions, tubular basement membrane deposits, tissue ANA, glomerular deposition of IgG, IgM, IgA, C3, C4, and C1q. At the time of biopsy 148 patients had no clinical evidence for lupus, and 22 had a clinical diagnosis of lupus. Six additional patients eventually developed overt lupus after an average of 12 months. Incidences of serologic and pathologic features in lupus as compared with nonlupus membranous glomerulopathy were determined. These data were used to calculate sensitivity, specificity, positive and negative predictive values, and overall efficiency of each parameter in differentiating between lupus and nonlupus membranous glomerulopathy. In general, serologic, morphologic and immunohistopathologic features are more accurate at ruling out lupus than making the diagnosis of lupus. However, a number of features are significantly more frequent in lupus membranous glomerulopathy. Therefore, identification of these features, especially more than one, warrants a high suspicion of lupus rather than nonlupus membranous glomerulopathy even in patients without clinically overt systemic lupus erythematosus. The positive/negative predictive values of some of the pathologic features studied are as follows: mesangial dense deposits 63/99, subendothelial dense deposits 77/93, tubuloreticular inclusions 61/96, intense C1q deposition 47/95, tubular basement membrane deposits 100/87, and glomerular hypercellularity 26/86.Différentiation pathologique entre glomérulopathie extra-membraneuse lupique et non lupique. Les caractéristiques cliniques et pathologiques suivantes ont été évaluées chez 170 malades atteints de glomérulopathie extra-membraneuse documentée par microscopie électronique: l'âge, le sexe, la race, les critères de lupus de l'American Rheumatism Association, les ANA sériques, le complément sérique, l'hypercellularité glomérulaire, le stade des dépôts denses sous-épithéliaux, les inclusions endothéliales tubuloréticulaires, les dépôts dans la membrane basale tubulaire, les ANA tissulaires, les dépôts glomérulaires d'IgG, IgM, IgA, C3, C4, et C1q. Au moment de la biopsie, 148 malades n'avaient pas d'argument clinique pour un lupus, et 22 avaient un diagnostic clinique de lupus. Six malades supplémentaires ont développé un lupus patent après une moyenne de 12 mois. L'incidence des caractéristiques sérologiques et pathologiques dans la glomérulopathie extra-membraneuse lupique ou non lupique a été déterminée. Ces données ont été utilisées pour calculer la sensibilité, la spécificité, les valeurs prédictives positives et négatives, et l'efficacité globale de chaque paramètre pour différencier entre glomérulopathie extra-membraneuse lupique ou non lupique. D'une façon générale, les caractéristiques sérologiques, morphologiques et immunohistopathologiques sont plus puissantes pour éliminer le lupus que pour faire le diagnostic de lupus. Cependant, un certain nombre de caractéristiques sont significativement plus fréquentes dans la glomérulopathie extra-membraneuse lupique. C'est pourquoi la mise en évidence de ces caractéristiques, surtout s'il y en a plus d'une, apporte une forte suspicion de glomérulopathie extra-membraneuse plus lupique que non lupique, même chez des malades sans lupus erythémateux disséminé cliniquement patent. Les valeurs prédictives positives/négatives de certaines des caractéristiques pathologiques étudiées sont les suivantes: dépôts denses mésangiaux 63/99, dépôts denses sous-endothéliaux 77/93, inclusions tubuloréticulaires 61/96, dépôts intenses de C1q 47/95, dépôts dans la membrane basale tubulaire 100/87, et hypercellularité glomérulaire 26/86

ANCA Glomerulonephritis and Vasculitis

ANCA vasculitis has an associated autoimmune response that produces ANCAs that induce distinct pathologic lesions. Pauci-immune necrotizing and crescentic GN is a frequent component of ANCA vasculitis. ANCA vasculitis is associated with ANCA specific for myeloperoxidase (MPO-ANCA) or proteinase 3 (PR3-ANCA). A diagnosis of ANCA vasculitis should always specify the serotype as MPO-ANCA positive, PR3-ANCA positive, or ANCA-negative. To fully characterize a patient, the serotype also should be accompanied by the clinicopathologic variant if this can be determined: microscopic polyangiitis, granulomatosis with polyangiitis (Wegener), eosinophilic granulomatosis with polyangiitis (Churg-Strauss), or renal-limited vasculitis. ANCA vasculitis is most prevalent in individuals >50 years old. There are racial/ethnic and geographic influences on the prevalence, serotype frequencies, and clinicopathologic phenotypes. There is clinical, in vitro, and animal model evidence that ANCAs cause disease by activating neutrophils to attack small vessels. Immunomodulatory and immunosuppressive therapies are used to induce remission, maintain remission, and treat relapses. Over recent years, there have been major advances in optimizing treatment by minimizing toxic therapy and utilizing more targeted therapy

B cell-mediated pathogenesis of ANCA-mediated vasculitis

B cells and their progeny that produce and release anti-neutrophil cytoplasmic autoantibodies (ANCA) are the primary cause for an aggressive form of necrotizing small vessel vasculitis. Cytoplasmic ANCA antigens are released at the surface and in the microenvironment of cytokine-primed neutrophils. Binding of ANCA to ANCA antigens activates neutrophils by both Fc receptor engagement and direct Fab’2 binding to antigen on the cell surface. ANCA-activated neutrophils release factors that induce alternative complement pathway activation, which establishes a potent inflammatory amplification loop that causes severe necrotizing vascular inflammation. The origin of the ANCA autoimmune response is unknown but appears to involve genetically determined HLA specificities that allow the autoimmune response to develop. One putative immunogenic mechanisms begins with an immune response to a peptide that is complementary to the autoantigen and evolves through an anti-idiotypic network to produce autoantibodies to the autoantigen. Another putative immunogenic mechanism begins with an immune response to a microbe-derived molecular mimic of the autoantigen resulting in antibodies that cross-react with the autoantigen. Release of neutrophil extracellular traps, apoptosis and increased granule protein expression of ANCA antigens may facilitate the initiation of an ANCA autoimmune response, augment established pathogenic ANCA production, or both. The ANCA B cell autoimmune response is facilitated by quantitatively and qualitatively impaired T cell and B cell suppression, and by release from activated neutrophils of B cell activating factors that enhance B cell proliferation and retard B cell apoptosis

Complement in ANCA-Associated Vasculitis

Antineutrophil cytoplasmic autoantibodies (ANCA) are the likely cause for necrotizing small vessel vasculitis and crescentic glomerulonephritis. Unlike other forms of crescentic glomerulonephritis induced by immune complexes or anti-glomerular basement membrane (anti-GBM) antibodies that have conspicuous vessel wall immunoglobulin and complement, there is a paucity, although usually not an absence, of vessel wall immunoglobulin and complement in ANCA-associated glomerulonephritis. In spite of this comparatively lower level and more localized distribution of vessel wall complement, experimental and clinical observations strongly incriminate alternative complement pathway activation as critically important in the pathogenesis of ANCA disease. Experimental data in animal models and in vitro experiments demonstrate that primed neutrophils are activated by ANCA, which generates C5a that engages C5a receptors on neutrophils. This attracts and in turn primes more neutrophils for activation by ANCA. In patients with ANCA disease, plasma levels of C3a, C5a, soluble C5b-9 and Bb have been reported to be higher in active disease than in remission, whereas no difference was reported in plasma C4d in active versus remission ANCA disease. Thus, experimental and clinical data support the hypothesis that ANCA-induced neutrophil activation activates the alternative complement pathway and generates C5a. C5a not only recruits additional neutrophils through chemotaxis but also primes neutrophils for activation by ANCA. This creates a self-fueling inflammatory amplification loop that results in the extremely destructive necrotizing vascular injury

Anti-myeloperoxidase antibodies stimulate neutrophils to damage human endothelial cells

Anti-myeloperoxidase antibodies stimulate neutrophils to damage human endothelial cells. Anti-myeloperoxidase autoantibodies are found in association with idiopathic necrotizing glomerulonephritis and systemic vasculitis. It is not known if their presence is an epiphenomen or an integral part of the pathogenic process. To further delineate their hypothesized pathogenicity, we studied their ability to stimulate neutrophils to damage human umbilical vein endothelial cells in vitro. Anti-myeloperoxidase antibodies from human, rabbit and mouse sources were utilized. These antibodies stimulated neutrophils to damage endothelial cells as determined by 51Cr release. The effect was dependent on priming the neutrophils with tumor necrosis factor-α, and further enhanced with the addition of endotoxin. The amount of endothelial cell damage was dependent on the dose of anti-myeloperoxidase, the source of the neutrophils, the concentration of TNF, and the presence of endotoxin. Under identical conditions, control antibodies did not stimulate neutrophils to damage endothelial cells. The effect was confirmed by labeling the endothelial cells with 3H-adenine which yielded the same results. These results provide further in vitro evidence that anti-myeloperoxidase autoantibodies may play a significant role in the pathogenesis of idiopathic pauci-immune glomerulonephritis and vasculitis

Low incidence of IgA nephropathy in Blacks

Low incidence of IgA nephropathy in blacks. The clinical and pathologic features were evaluated in 106 IgA nephropathy patients identified in 1,753 consecutive patients undergoing renal biopsy in the southeastern United States. Special attention was paid to the proportion of Blacks among the IgA nephropathy patients compared with non-IgA nephropathy patients, and any differences in clinical or pathologic findings between Whites and Blacks with IgA nephropathy. The incidence of IgA nephropathy was approximately six times lower in Blacks (6 out of 461) than in Whites (100 out of 1,292) undergoing renal biopsy (P < 0.001). There were no morphologic or immunohistopathologic differences between Whites and Blacks with IgA nephropathy. The only clinical difference was a marked shift in the male to female sex ratio from 3.5:1 in Whites to 1:5 in Blacks (P < 0.004). The low incidence and reversed sex ratio of IgA nephropathy in Blacks were also supported by a review of previously published data

Pathogenesis of antineutrophil cytoplasmic autoantibody vasculitis

Anti-neutrophil cytoplasmic autoantibodies (ANCA) are associated with vasculitis. Current therapy involves administration of toxic therapy that is not optimally effective. The review will summarize evidence for the pathogenicity of ANCA, which will suggest possible strategies for improving treatment

Collapsing glomerulopathy: A clinically and pathologically distinct variant of focal segmental glomerulosclerosis

Collapsing glomerulopathy: A clinically and pathologically distinct variant of focal segmental glomerulosclerosis. Sixteen patients with renal biopsy findings of extensive focal glomerular capillary collapse, visceral epithelial cell hypertrophy and hyperplasia, and variable degrees of tubulointerstitial injury in the absence of evidence for human immunodeficiency virus (HIV) infection or intravenous drug abuse were prospectively identified by renal biopsy. The pathologic process was designated collapsing glomerulopathy to distinguish it from other patterns of focal glomerular sclerosis. The clinical and pathologic characteristics of these 16 patients were analyzed and compared to a group of 25 patients with noncollapsing focal segmental glomerulosclerosis (FSGS). Thirteen of 16 patients with collapsing glomerulopathy were black as compared with 11 of 25 with FSGS (P = 0.018). The most common findings at presentation were hypertension and manifestations of the nephrotic syndrome. Although the duration of symptoms prior to presentation was no longer in the collapsing glomerulopathy group, the presenting mean serum creatinine was higher in patients with collapsing glomerulopathy than in those with noncollapsing FSGS (3.5 ± 3.4 mg/dl vs. 1.3 0.6 mg/dl, P = 0.001). Twenty-four-hour urine protein excretion was also higher in the collapsing glomerulopathy group (13.2 ± 7.7 g/day vs. 4.6 ± 4.5 g/day FSGS, P = 0.005). The collapsing glomerulopathy patients had a mean age of 41.4 ± 19.1 (range 19 to 81), a male-to-female ratio of 11:5 and a black-to-white ratio of 13:3. Renal survival, evaluated by life-table analysis, was markedly worse in collapsing glomerulopathy patients than in FSGS patients (P = 0.0004). It is proposed that collapsing glomerulopathy is a distinct entity characterized by black racial predominance, massive proteinuria, relatively rapidly progressive renal insufficiency, and distinctive pathologic findings. The data suggest that collapsing glomerulopathy is clinically, pathologically, and epidemiologically different from noncollapsing FSGS. Although collapsing glomerulopathy resembles HIV-nephropathy both pathologically and clinically, it differs clinically by having no evidence for associated HIV infection and differs pathologically by lacking endothelial tubuloreticular inclusions