Update on antiglomerular basement membrane disease

Anti-glomerular basement membrane (GBM) antibody disease is an autoantibody-mediated disorder that usually presents as rapidly progressive glomerulonephritis, often with pulmonary hemorrhage (the Goodpasture syndrome). It is reported that patients with severe renal failure do not generally recover renal function. To examine the long-term outcome of severe anti-GBM antibody disease. Retrospective review of patients treated for confirmed anti-GBM antibody disease over 25 years. A tertiary referral center in the United Kingdom. 71 treated patients with anti-GBM antibody disease. All patients received plasma exchange, prednisolone, and cyclophosphamide. Patient and renal survival, renal histology, and antibody levels. Patients who presented with a creatinine concentration less than 500 micromol/L (5.7 mg/dL) (n = 19) had 100% patient survival and 95% renal survival at 1 year and 84% patient survival and 74% renal survival at last follow-up. In patients who presented with a creatinine concentration of 500 micromol/L or more (>/=5.7 mg/dL) (n = 13) but did not require immediate dialysis, patient and renal survival were 83% and 82% at 1 year and 62% and 69% at last follow-up. In patients who presented with dialysis-dependent renal failure (n = 39), patient and renal survival were 65% and 8% at 1 year and 36% and 5% at last follow-up. All patients who required immediate dialysis and had 100% crescents on renal biopsy remained dialysis dependent. Patients with the Goodpasture syndrome and severe renal failure should be considered for urgent immunosuppression therapy, including plasma exchange, to maximize the chance of renal recovery. Patients needing immediate dialysis are less likely to recover.

Patients have been described who have both anti-neutrophil cytoplasm antibodies (ANCA) and anti-glomerular basement membrane (GBM) antibodies. We have attempted to define the true prevalence of such "double positive" patients, and describe in detail their clinical features and outcome. We have reviewed all serologic assays performed between 1990 and 2000 in a single institution, and the case notes of patients having sera positive for both ANCA and anti-GBM antibodies. During this time 20,392 sera were initially tested for ANCA, and 4808 sera tested for anti-GBM antibodies. Five percent of all ANCA-positive serum samples were also positive for anti-GBM antibodies, and 32% of all anti-GBM positive samples had detectable ANCA. Of 27 patients with both antibodies, 82% had anti-myeloperoxidase specific P-ANCA. Pulmonary hemorrhage occurred in 44%. Renal biopsy showed extensive glomerular cellular crescents in most patients. Patient and renal survival rates were 52% and 26%, respectively, at one year. Sixty-eight percent of patients were dialysis-dependent at presentation, and none of these recovered renal function, despite immunosuppression with or without plasma exchange. Serologic evidence of double positivity for both ANCA and anti-GBM antibodies is common in patients with either antibody. In our study these patients have a poor prognosis when presenting with severe disease and initially behave more like anti-GBM disease than vasculitis. Recovery from severe renal failure is rare.

In Goodpasture's disease, circulating autoantibodies bind to the noncollagenous-1 (NC1) domain of type IV collagen in the glomerular basement membrane (GBM). The specificity and molecular architecture of epitopes of tissue-bound autoantibodies are unknown. Alport's post-transplantation nephritis, which is mediated by alloantibodies against the GBM, occurs after kidney transplantation in some patients with Alport's syndrome. We compared the conformations of the antibody epitopes in Goodpasture's disease and Alport's post-transplantation nephritis with the intention of finding clues to the pathogenesis of anti-GBM glomerulonephritis. We used an enzyme-linked immunosorbent assay to determine the specificity of circulating autoantibodies and kidney-bound antibodies to NC1 domains. Circulating antibodies were analyzed in 57 patients with Goodpasture's disease, and kidney-bound antibodies were analyzed in 14 patients with Goodpasture's disease and 2 patients with Alport's post-transplantation nephritis. The molecular architecture of key epitope regions was deduced with the use of chimeric molecules and a three-dimensional model of the alpha345NC1 hexamer. In patients with Goodpasture's disease, both autoantibodies to the alpha3NC1 monomer and antibodies to the alpha5NC1 monomer (and fewer to the alpha4NC1 monomer) were bound in the kidneys and lungs, indicating roles for the alpha3NC1 and alpha5NC1 monomers as autoantigens. High antibody titers at diagnosis of anti-GBM disease were associated with ultimate loss of renal function. The antibodies bound to distinct epitopes encompassing region E(A) in the alpha5NC1 monomer and regions E(A) and E(B) in the alpha3NC1 monomer, but they did not bind to the native cross-linked alpha345NC1 hexamer. In contrast, in patients with Alport's post-transplantation nephritis, alloantibodies bound to the E(A) region of the alpha5NC1 subunit in the intact hexamer, and binding decreased on dissociation. The development of Goodpasture's disease may be considered an autoimmune "conformeropathy" that involves perturbation of the quaternary structure of the alpha345NC1 hexamer, inducing a pathogenic conformational change in the alpha3NC1 and alpha5NC1 subunits, which in turn elicits an autoimmune response. (Funded by the National Institute of Diabetes and Digestive and Kidney Diseases.) 2010 Massachusetts Medical Society