Comparison of anti-GBM antibodies in sera with or without ANCA

Crescentic glomerulonephritis: new aspects of pathogenesis

This review provides a summary of recent advances in the understanding of crescentic glomerulonephritis, focusing on antineutrophil cytoplasm antibody (ANCA)-associated vasculitis and anti-glomerular basement membrane (anti-GBM) antibody disease. In ANCA-associated vasculitis (AAV), four main conceptual advances are discussed as follows: (1) evidence for the pathogenicity of ANCA, (2) molecular mimicry and the role of infection in AAV, (3) evidence for aberrant T-cell responses and T-cell regulation in AAV, and (4) advances in understanding of genetic predisposition to AAV. In relation to anti-GBM disease we discuss the following: (1) the nature of the Goodpasture autoantigens, (2) T-cell responses and regulation in anti-GBM disease, and (3) human leukocyte antigen and non-human leukocyte antigen genetic associations.

Anti-hLAMP2-antibodies and dual positivity for anti-GBM and MPO-ANCA in a patient with relapsing pulmonary-renal syndrome

BACKGROUND

Pulmonary-renal syndrome associated with anti-glomerular basement membrane (GBM) antibodies, also known as Goodpasture's syndrome, is a rare but acute and life-threatening condition. One third of patients presenting as anti-GBM antibody positive pulmonary-renal syndrome or rapidly progressive glomerulonephritis are also tested positive for anti-neutrophil cytoplasmic antibodies (ANCA). Whilst anti-GBM disease is considered a non-relapsing condition, the long-term course of double-positive patients is less predictable.

CASE PRESENTATION

We report a patient with such dual positivity, who presented with pulmonary hemorrhage, crescentic glomerulonephritis and membranous nephropathy. Plasmapheresis in combination with immunosuppressive therapy led to a rapid remission but the disease relapsed after two years. The serum of the patient was tested positive for antibodies to human lysosomal membrane protein 2 (hLAMP2), a novel autoantigen in patients with active small-vessel vasculitis (SVV). The anti-hLAMP2 antibody levels correlated positively with clinical disease activity in this patient.

CONCLUSION

We hypothesize that this antibody may indicate a clinical course similar to ANCA-associated vasculitis in double-positive patients. However, this needs to be confirmed on comprehensive patient cohorts.

Performance evaluation of a novel chemiluminescence assay for detection of anti-GBM antibodies: an international multicenter study

BACKGROUND

Autoantibodies to the non-collagen region (NC1) of the alpha-3 subunit of collagen IV represent a serological hallmark in the diagnosis of Goodpasture's syndrome (GPS). The objective of our study was to carefully analyze the performance characteristics of a novel anti-glomerular basement membrane (GBM) chemiluminescence immunoassay (CIA).

METHODS

Sera from patients with GPS (n = 90) were collected from four clinical centers. Samples from different disease groups (n = 397) and healthy individuals (n = 400) were used as controls. All samples were tested for anti-GBM antibodies by a rapid, random access CIA (QUANTA Flash™ GBM). Most of the samples were also tested using other methods including different commercial anti-GBM IgG assays and research assays for anti-GBM IgA and IgM.

RESULTS

The sensitivity and specificity of the novel CIA was 95.6% [95% confidence interval (CI) 89.0-98.8%] and 99.6% (95% CI 98.9-99.9%), respectively. Receiver operating characteristic analysis showed good discrimination between GPS patients and controls. The area under the curve was 0.98 (CI 0.96-1.0). The three anti-GBM antibody-positive samples from the control group were from two healthy individuals and one human immunodeficiency virus (HIV)-infected patient. All three individuals had low levels of anti-GBM antibodies [20, 24 and 25 chemiluminescent unit (CU), cutoff 20 CU]. When the results of the new CIA were compared to other methods, good agreement was observed: 95.8% (kappa = 0.92) versus EliA™ GBM, 97.4% (kappa = 0.95) versus both BINDAZYME™ Anti-GBM and QUANTA Lite® GBM. Anti-GBM IgA was detectable in low concentrations in patients with GPS and was associated with anti-GBM IgG but was less useful in discriminating GPS patients and controls. No discrimination was found for anti-GBM IgM.

CONCLUSION

The novel QUANTA Flash™ GBM CIA demonstrated good sensitivity and specificity and had good agreement with other methods. Our data confirm that ∼5% of patients with GPS do not have detectable levels of anti-GBM antibodies.

Anti-glomerular basement membrane (anti-GBM) disease accompanied by vasculitis that was not positive for antineutrophil cytoplasmic antibodies to myeloperoxidase and proteinase 3: a report of two cases and the incidence of anti-GBM disease at one institution

BACKGROUND

Anti-glomerular basement membrane (anti-GBM) disease is thought to be distinct from vasculitis. In contrast, there have been several papers suggesting the presence of angiitis in cases that were positive for anti-GBM antibody (Ab), as well as for either myeloperoxidase (MPO)- or proteinase 3 (PR3)-anti-neutrophil cytoplasmic antibody (ANCA) (Group I). We experienced four patients who had anti-GBM Abs, but not MPO- and PR3-ANCA (Group II), and two of these patients were found to have vasculitis. Therefore, we performed an in-depth study on these two patients.

METHODS

The patients with anti-GBM disease were isolated from 578 cases whose renal tissues were examined, and they were categorized into two groups. We have already published the data about Group I. We then proceeded to study two vasculitic patients in Group II clinically, pathologically, and serologically. The anti-GBM Ab and ANCA levels were detected by enzyme-linked immunosorbent assays. Renal specimens were studied by routine staining as well as immunohistochemical investigations of CD31 and type IV collagen.

RESULTS

The total number of patients with anti-GBM disease was 7 (7/578 = 1.2%), with 3 patients belonging to Group I and 4 patients belonging to Group II. Two patients in Group II were diagnosed to have vasculitis, but the remaining 2 patients did not. One vasculitic patient was complicated by pulmonary hemorrhage, while the other vasculitic patient displayed peripheral neuropathy as well as a small cavity lesion in the lung. The latter patient was found to be positive for perinuclear (p)-ANCA, but not for any other ANCA subsets. The renal pathology in the two vasculitic patients showed crescentic glomerulonephritis (CSGN) and immunoglobulin (Ig) G linear deposits along the glomerular capillary loops. The former patient showed fibrinoid angiitis in an afferent arteriole as well as peritubular capillaritis. The latter patient demonstrated peritubular capillaritis. These peritubular capillaritides were diagnosed by the loss of CD31 and type IV collagen staining, the blurred appearance of peritubular capillary walls by periodic acid-Schiff staining, and the pericapillary infiltration of inflammatory cells.

CONCLUSION

The incidence of anti-GBM disease was very low, and our patients were categorized into two groups (Groups I and II) based on whether or not they were positive for MPO- or PR3-ANCA. Two patients in Group II were found to have vasculitis. According to our results, we concluded that the anti-GBM disease of Group II could also be associated with vasculitis.

Dual myeloperoxidase-antineutrophil cytoplasmic antibody- and antiglomerular basement membrane antibody-positive cases associated with prior pulmonary fibrosis: a report of four cases

BACKGROUND

Both myeloperoxidase-associated antineutrophil cytoplasmic antibody (MPO-ANCA) and antiglomerular basement membrane antibody (anti-GBM Ab) positivity have been demonstrated in patients with rapidly progressive glomerulonephritis (RPGN), either with or without pulmonary hemorrhage; however, the implications of these antibodies in such patients have not yet been elucidated. The cases with dual positive antibodies were studied clinically, serologically, and pathologically, and the implications of antibodies are discussed here.

PATIENTS AND METHODS

Four patients with prior pulmonary fibrosis, who subsequently developed RPGN and pulmonary hemorrhage, were studied clinically, serologically, and pathologically. The clinical data were reviewed extensively and the dual positive antibodies were detected by enzyme-linked immunosorbent assays. Pathological studies were performed with a renal biopsy in one patient, a gastric biopsy in another patient, and autopsy materials in the remaining 2 patients.

RESULTS

All 4 patients had prior pulmonary fibrosis before the symptoms of RPGN when the dual positivity of MPO-ANCA and anti-GBM Ab was detected. Three cases were accompanied by pulmonary hemorrhage around the time of RPGN whereas the remaining case demonstrated pulmonary hemorrhage a few years later. Renal tissue specimens in 3 cases showed circumferential crescents and linear immunoglobulin G deposits along the glomerular capillary loops in glomeruli. Two autopsy specimens revealed vasculitis of the small arteries and arterioles of the kidney, and one of them showed similar vasculitic findings in both the gastrointestinal tract walls and the adipose tissues of the adrenal glands. Additionally, a case with pulmonary hemorrhage occurring after remission was associated with re-elevated MPO-ANCA levels but without anti-GBM Ab positivity. A gastric biopsy was unremarkable and non-contributory for the diagnosis, but this case showed vasculitic symptoms of peripheral neuritis and retinal hemorrhage. Taken together, all 4 cases demonstrated prior pulmonary fibrosis and dual positivity of MPO-ANCA as well as anti-GBM Abs at the time of RPGN, and were associated with either pulmonary hemorrhage or its occurrence thereafter.

CONCLUSION

Four cases that showed prior pulmonary fibrosis as well as subsequent RPGN and pulmonary hemorrhage were both MPO-ANCA- and anti-GBM Ab-positive at the time of RPGN. The glomeruli disclosed features compatible with anti-GBM Ab disease, but the clinical and pathological vasculitic manifestations, including prior pulmonary fibrosis that might be an early manifestation of ANCA disease, suggested the occurrence of MPO-ANCA-associated vasculitis. Furthermore, 1 case subsequently showed repetitive pulmonary hemorrhage with re-elevated MPO-ANCA positivity but without anti-GBM Ab positivity, and this event was possibly due to MPO-ANCA-associated alveolar capillaritis. As anti-GBM Ab disease is generally thought not to manifest the clinical and pathological features of vasculitis excluding the kidney, MPO-ANCA might be a key factor regarding the occurrence of this dual positive disease.

Recovery of renal function in a dialysis-dependent patient with microscopic polyangiitis and both myeloperoxidase anti-neutrophil cytoplasmic antibodies and anti-glomerular basement membrane antibodies

A 40-year-old man with microscopic polyangiitis developed both myeloperoxidase anti-neutrophil cytoplasmic antibodies (90 EU) and anti-glomerular basement membrane antibodies (134 EU)-positive rapidly progressive glomerulonephritis and heparin-induced thrombocytopenia. Although the patient initially showed no signs of improvement, persistent therapy including 1 g/day intravenous methylprednisolone, 50 mg/day oral prednisolone, plasma exchange, and 900 mg/day intravenous cyclophosphamide resulted in the normalization of both titers, recovery of renal function, and discontinuation of dialysis. Though previous studies showed poor outcomes in such "double-positive" patients, aggressive immunosuppression in younger patients may result in the recovery of renal function, even in those with severe renal dysfunction.

Clinical features and outcomes of anti-glomerular basement membrane disease in older patients

BACKGROUND

Anti-glomerular basement membrane (GBM) disease is being recognized increasingly in older patients. Disease presentation and outcomes of these patients are unclear.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

221 consecutive Chinese patients with anti-GBM disease diagnosed in 1998-2008 in our tertiary referral center. Anti-GBM disease was defined as positive anti-GBM antibodies in circulation and/or linear immunoglobulin G deposition along the GBM on kidney biopsy.

PREDICTOR

Older age, defined as 65 years or older, and antineutrophil cytoplasmic antibody, detected using immunofluorescence and enzyme-linked immunosorbent assay, at presentation.

OUTCOMES

Clinical features, kidney pathologic characteristics, end-stage renal disease (ESRD), and mortality. Multivariate Cox proportional hazard models were used to assess the contribution of age, sex, clinical measures, and treatments to ESRD and mortality.

RESULTS

50 of 221 (22.6%) patients were 65 years or older. Older patients had a male predominance (male/female ratio, 1.9:1). They had a higher proportion of positive antineutrophil cytoplasmic antibody results (46.0% vs 14.6%; P < 0.001), lower prevalence of hemoptysis (26.0% vs 46.2%; P = 0.01), lower urine protein excretion (1.4 ± 1.0 vs 3.9 ± 3.3 g/d; P = 0.001), and higher estimated glomerular filtration rate (eGFR) at presentation (8.4 vs 5.1 mL/min/1.73 m(2); P = 0.007) compared with younger patients. During follow-up, 30 of 37 (81.1%) and 21 of 37 (56.8%) patients developed ESRD and died in the older group compared with 115 of 139 (82.7%) and 35 of 139 (25.2%) in the younger group (P = 0.1 and P = 0.001, respectively). For older patients, multivariate Cox regression analysis showed that higher initial eGFR was an independent predictor for both ESRD (HR, 0.86; 95% CI, 0.78-0.96; P = 0.005) and death (HR, 0.79; 95% CI, 0.66-0.94; P = 0.008).

LIMITATIONS

Not all patients underwent kidney biopsy, especially those with very old age or ESRD at presentation.

CONCLUSIONS

Older patients with anti-GBM disease had milder kidney damage and less pulmonary involvement. Outcomes were predicted by initial eGFR. Thus, early diagnosis was crucial to improve outcomes.

Microscopic polyangiitis

In 1923, Friedrich Wohlwill described two patients with a "microscopic form of periarteritis nodosa," which was distinct from the classical form. This disease, now known as microscopic polyangiitis (MPA), is a primary systemic vasculitis characterized by inflammation of the small-caliber blood vessels and the presence of circulating antineutrophil cytoplasmic antibodies. Typically, microscopic polyangiitis presents with glomerulonephritis and pulmonary capillaritis, although involvement of the skin, nerves, and gastrointestinal tract is not uncommon. Treatment of MPA generally requires use of a cytotoxic agent (such as cyclophosphamide) in addition to high-dose glucocorticoids. Recent research has focused on identifying alternate treatment strategies that minimize or eliminate exposure to cytotoxic agents. This article reviews the history, pathogenesis, clinical manifestations, and treatment of MPA.

Pulmonary Renal Syndrome Due to Anti-GBM and IgM C-ANCA Disease Requiring the Use of Novel Therapeutic Agents

There are several known causes for the clinical syndrome of pulmonary hemorrhage and acute renal failure. Here, we report a unique case of a 50-year-old man presenting in this manner. The initial diagnosis was one of antiglomerular basement membrane (anti-GBM) disease that responded well to steroids, cyclophosphamide, and plasma exchange (PE). The pulmonary hemorrhage resolved, but he remained dialysis dependent. However, despite falling anti-GBM titers, the symptoms relapsed and standard therapy was reinitiated with limited success. The anti-GBM antibody titer fell to zero despite clinical deterioration, prompting a search for an alternative diagnosis. He was found to be IgM anti-proteinase-3 antineutrophil cytoplasmic antibody (C-ANCA) positive. The pulmonary hemorrhage responded successfully to the use of intravenous immunoglobulin and the antilymphocyte monoclonal antibody CD52. To our knowledge, this is the first known case of IgM C-ANCA in association with anti-GBM disease. As such, it highlights the predominance of pulmonary hemorrhage in this condition, as well as the need to consider alternative therapies in refractory cases.

Antigenic heterogeneity of IgA anti-GBM disease: new renal targets of IgA autoantibodies

Anti-glomerular basement membrane (anti-GBM) disease is an aggressive form of glomerulonephritis, usually mediated by immunoglobulin G (IgG) autoantibodies to the noncollagenous (NC1) domain of alpha 3(IV) collagen. Less is known about the target antigen(s) in patients with atypical anti-GBM disease involving IgA autoantibodies. We report a new case of IgA anti-GBM disease in a patient with a history of proliferative lupus nephritis who presented with increasing creatinine levels, proteinuria, and hematuria, but no clinical or serological evidence of lupus recurrence. Renal biopsy showed focal and segmental necrotizing glomerulonephritis with strong linear capillary loop IgA staining by means of immunofluorescence. Serological test results were negative for IgG or IgA autoantibodies against the alpha 3NC1 domain. By means of immunoblotting, IgA from patient serum bound to 38- to 48-kd antigens collagenase-solubilized from human GBM, but not to purified NC1 domains of GBM collagen IV. The target of patient's IgA autoantibodies thus was identified as a novel GBM antigen, distinct from the alpha 3NC1 domain or other known targets of anti-GBM IgA autoantibodies. Clinical resolution was attained by means of conventional treatment with steroids and cyclophosphamide. The diversity of antigens recognized by anti-GBM IgA autoantibodies highlights the importance of renal biopsy for the reliable diagnosis of this rare condition because conventional serological immunoassays likely would yield false-negative results.

Characteristics and Outcome of Chinese Patients with Both Antineutrophil Cytoplasmic Antibody and Antiglomerular Basement Membrane Antibodies

BACKGROUND

Antineutrophil cytoplasmic antibody (ANCA)-associated systemic vasculitis (AASV) is a systemic autoimmune disease. A number of cases have been found to have antiglomerular basement membrane (GBM) antibody-positive serum. The purpose of the current article is to investigate the prevalence of anti-GBM antibodies in sera from a large cohort of Chinese patients with AASV and to characterize the clinical and pathological features of the 'double positive' patients.

METHODS

Sera from 652 patients with AASV were screened by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot analysis using purified human alpha(IV)NC1 as antigen. Antigen specificity of anti-GBM antibodies was determined by ELISA using recombinant human alpha 3(IV)NC1 as solid phase ligand. Clinical and pathological data of patients with both ANCA and anti-GBM antibodies were analyzed retrospectively.

RESULTS

61/652 (9.36%) sera from patients with AASV were serum anti-GBM antibody positive and all recognized recombinant human alpha 3(IV)NC1. All the cases had renal involvement, 37/48 (77.1%) cases had pulmonary involvement, non-specific symptoms and other multisystem involvements were common. The renal survival was 14.6% (7/48) and patient survival was 37.5% (18/48) respectively at the end of 1 year. The following factors predicted poor prognosis: (1) serum creatinine >700 micromol/l (p = 0.034); (2) oliguria or anuria on diagnosis (p = 0.001); (3) high percentage (>85%) of glomeruli with crescents (p = 0.011); (4) high titer anti-GBM antibodies (p = 0.003), and (5) hemoptysis (p = 0.049).

CONCLUSION

Patients with double antibodies were not rare in AASV. They had multisystem involvement but poor short-term prognosis.Anti-GBM antibodies should be detected on diagnosis of AASV, especially for old ages.

Antigen and Epitope Specificity of Anti–Glomerular Basement Membrane Antibodies in Patients with Goodpasture Disease with or without Anti-Neutrophil Cytoplasmic Antibodies

Goodpasture disease (GP) is defined by the presence of anti-glomerular basement membrane (anti-GBM) antibodies and rapidly progressive glomerulonephritis. Besides anti-GBM, many patients with GP produce anti-neutrophil cytoplasmic antibodies (ANCA). For elucidation of the pathophysiologic significance of ANCA in this setting, epitope and antigen specificity of the anti-GBM antibodies and antigen specificity of ANCA were studied. Bovine testis alpha(IV)NC1 (tNC1); recombinant human alpha1, alpha3, alpha4, and alpha5(IV)NC1 (ralpha1 through ralpha5); and three chimeric proteins that contain previously defined epitope regions designated E(A), E(B), and S2 were used to examine the anti-GBM antibodies by ELISA in 205 Chinese patients with GP with or without ANCA. In the 205 anti-GBM antibody-positive sera, 63 (30.7%) were also ANCA positive (61 myeloperoxidase-ANCA and six proteinase 3-ANCA, four being triple positive). All 205 sera recognized tNC1 and ralpha3(IV)NC1. In the double-positive group, 54.0, 66.7, 71.4% of the sera could recognize ralpha1, ralpha4, and ralpha5, respectively, compared with 49.3, 60.6, and 55.6% for patients with anti-GBM antibodies alone. The levels of the antibodies to ralpha3, tNC1, and the alpha3/alpha1 ratio were lower in the double-positive group than that in patients with anti-GBM antibody alone (P < 0.05). Most of the sera could recognize the epitope regions E(A), E(B), and S2, but the absorbance values to E(A), E(B), and S2 were lower in double-positive group (P < 0.05). Double-positive patients had a broader spectrum of anti-GBM antibodies and lower levels of antibodies against alpha3(IV)NC1 compared with that of patients with anti-GBM antibodies alone.

Glomérulonéphrites extracapillaires

Crescentic glomerulonephritis are characterised by a crescent shaped cellular proliferation that may lead to glomerular destruction. Over 50% of at least 10 analysed glomeruli should be affected. The search for immune deposits by immunofluorescence is an important diagnostic step. Patients present with rapidly progressive glomerulonephritis (RPGN): renal failure, proteinuria and haematuria. Extra-renal symptoms may help diagnosis. Diseases are classified in three groups according to immunofluorescence studies. Group I is characterised by linear deposits along the glomerular basement membrane (GBM) with anti-GBM auto-antibodies responsible for Goodpasture's disease. Group II put together various diseases with immune complex deposits. In group III, no significant immune deposits are found. Those "pauci-immune" glomerulonephritis are secondary to anti-neutrophil cytoplasmic antibodies (ANCA) positive systemic vasculitis, mainly Wegener's granulomatosis and microscopic polyangiitis. Primary glomerulonephritis may also be associated with crescent formation. Treatment is urgently required. Diagnosis is suspected in the context of extra-renal symptoms or immunological abnormalities, and confirmed by a kidney biopsy, that also helps to define prognosis. Apart from some group II glomerulonephritis, the induction treatment is often an association of steroids and cyclophosphamide, with plasma exchange in case of Goodpasture's disease. After remission, a maintenance treatment is required for ANCA-positive vasculitis to prevent relapses. The high rate of opportunistic infections and cancer give the rational for searching less aggressive therapeutic options.

Anti-glomerular basement membrane antibodies in the diagnosis of Goodpasture syndrome: a comparison of different assays

BACKGROUND

The role of anti-glomerular basement membrane (GBM) antibodies in the pathogenesis of Goodpasture syndrome (GPS) is firmly established. Untreated, the disease may follow a fulminating course. Early identification of patients has important implications in terms of management and prognosis. Therefore, a diagnostic test for the determination of circulating anti-GBM antibodies, of very high sensitivity and specificity, is necessary. A number of assays, using different antigenic substrates, are available, but studies comparing the 'performances' of the different tests are scarce.

METHODS

The aim of our work was to evaluate the sensitivity and specificity of four immunoassay-based anti-GBM antibodies kits. Thirty-four serum samples from 19 GPS patients, 41 pathological and 28 normal controls were studied retrospectively (the follow-up samples were not included in the analysis of performance data). Cut-off limits were derived from receiver operating characteristics curve analysis.

RESULTS

All the assays showed a comparable good sensitivity (between 94.7 and 100.0%), whereas specificity varied considerably (from 90.9 to 100.0%). The better performance in terms of sensitivity/specificity was achieved by a fluorescence immunoassay which utilizes a recombinant antigen.

CONCLUSION

All the assays have a good performance, with high sensitivity; however, the specificity may vary considerably.

Coexistence of Anti-Glomerular Basement Membrane Antibodies and Myeloperoxidase-ANCAs in Crescentic Glomerulonephritis

BACKGROUND

In a substantial proportion of patients with crescentic glomerulonephritis (CGN), both anti-glomerular basement membrane (GBM) antibodies and antineutrophil cytoplasmic antibodies (ANCAs) with specificity for myeloperoxidase (MPO-ANCA) are detected. In the present study, we questioned whether histological and clinical features of patients with both ANCA and anti-GBM antibodies differ from those of patients with either ANCA or anti-GBM alone.

METHODS

We reviewed the Limburg renal biopsy registry (1978 to 2003; n = 1,373) for cases of CGN. The presence of linear fluorescence on renal biopsy and the presence of ANCA and/or anti-GBM antibodies were measured. Subsequently, we assessed patient characteristics and follow-up and compared histological findings among the different groups.

RESULTS

We identified 46 MPO-ANCA-positive, 10 double-positive, and 13 anti-GBM-positive patients. Mean ages were 63, 64, and 52 years (P = 0.04), and serum creatinine levels were 5.0, 10.3, and 9.6 mg/dL (445, 910, and 850 micromol/L), respectively (P = 0.01). Granulomatous periglomerular inflammation was found in either MPO-ANCA- or double-positive patients, but not in anti-GBM-positive patients with CGN without MPO-ANCAs. Patient survival among the 3 groups was different, although not statistically significant (log rank P = 0.17, with 75%, 79%, and 100% alive at 1 year, respectively). Renal survival analysis showed significant differences among the 3 groups (P = 0.04, with 65%, 10%, and 15% off dialysis therapy at 1 year, respectively).

CONCLUSION

In patients with both anti-GBM antibodies and MPO-ANCAs, histological findings differ from those of patients with anti-GBM antibodies only. However, renal survival in these patients is not better than that in anti-GBM-positive patients and is worse compared with patients with MPO-ANCAs only.

Characteristics and Prognosis of Chinese Patients with Anti-Glomerular Basement Membrane Disease

BACKGROUND

Patients with anti-glomerular basement membrane (GBM) disease were predominantly reported in Caucasian population and reports from Chinese were lacking. The general picture of Chinese patients with anti-GBM disease was still unclear. This study is to investigate the characteristics and prognosis of Chinese patients with anti-GBM disease.

METHODS

Data from 105 patients with anti-GBM disease diagnosed in our hospital, between 1997 and 2002, were analyzed retrospectively. All the 105 sera were screened by enzyme-linked immunosorbent assay (ELISA) using highly purified bovine alpha(IV)NC1 as solid phase ligands. Clinical and pathological data of 69 patients with complete clinical remission (n = 5), partial remission (n = 10), and treatment failure (n = 54) were compared and the prognostic factors were evaluated.

RESULTS

Patients increased chronologically and three quarters of the 105 patients were diagnosed in the last 3 years. Most of the patients were between 20 and 29 years (n = 31) and a smaller second peak was found in patients over 60 years. 25/105 (24%) were also ANCA-positive. Patients with both anti-GBM antibodies and ANCA positive were elder (50 +/- 19 vs. 34 +/- 15 years, p < 0.01) and female predominant (15/25 vs. 16/80, p < 0.05). 56/97 (58%) patients presented as Goodpasture syndrome, 40/97 (41%) patients presented as rapidly progressive glomerulonephritis and one patient had pulmonary hemorrhage only. The following factors predict poor prognosis: (1) serum creatinine more than 600 micromol/l on diagnosis (p < 0.01); (2) oliguria or anuria on diagnosis (p < 0.01); (3) a high percentage (>85%) of glomeruli had crescents (p < 0.01), and (4) renal involvement before pulmonary hemorrhage (p < 0.05). Patients with serum creatinine over 600 micromol/l on diagnosis had higher levels of anti-GBM antibodies (106 +/- 48% vs. 73 +/- 40%, p < 0.01). Intensive plasma exchange therapy predicts a better prognosis in the patients with serum creatinine less than 600 mumol/l (p < 0.05).

CONCLUSIONS

Anti-GBM disease is not rare in China and behaves similarly to elsewhere. Early diagnosis and intensive plasmapheresis might be the most promising approaches to improve the outcome.

Clinical features and outcome of patients with both ANCA and anti-GBM antibodies

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSION

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.

Incidence and outcome of antiglomerular basement membrane disease in Chinese

BACKGROUND

Antiglomerular basement membrane (anti-GBM) disease is an uncommon disease, especially among Asian population. Many reports and studies on this condition in the Caucasian population are available, but little information exists on anti-GBM disease in Asians. To study the incidence and clinical characteristics of anti-GBM disease among Chinese patients, we reviewed our experience of anti-GBM disease in our hospital (Queen Mary Hospital, Hong Kong) from 1992 to 2003.

METHODS

All patients who were admitted for acute renal impairment, which was caused by crescentic glomerulonephritis associated with linear immunoglobulin G (IgG) staining on immunofluorescence, were included in the analysis. Serum anti-GBM antibodies were detected by either enzyme-linked immunofluorescence or indirect immunofluorescence. Ten patients were treated for anti-GBM disease during this 11-year period, yielding an incidence of approximately 0.6 cases per million population per year.

RESULTS

In this cohort, anti-GBM disease predominantly affected older patients (mean age: 58.6 +/- 21.7 years). Eight patients were aged between 60 and 80 years and there was a female preponderance (M:F = 2:8). The 1-year renal and patient survival was 15% (95% CI 0-40%) and 70% (95% CI 42-98%), respectively. Most patients presented with non-specific symptoms as well as impaired renal function. Detection of anti-GBM antibody provided a good screening test for the disease. Antiglomerular basement membrane antibodies were not detected in two patients. All but two patients received steroid, cyclophosphamide and intensive plasmapheresis therapy. Haemoptysis occurred in four patients (40%), and usually lagged behind the renal presentation and commencement of treatment. Six patients required long-term dialysis after the acute disease. Three patients died from the disease, two died from pulmonary complications and one died suddenly after a partial recovery of renal function.

CONCLUSION

Antiglomerular basement membrane disease is uncommon among the Chinese population. It predominantly affects older patients, and prognosis is poor. Long-term preservation of renal function after the initial attack is unusual.

Pathogenesis of Goodpasture syndrome: a molecular perspective

Goodpasture (GP) syndrome is a form of anti-glomerular basement membrane (GBM) disease, in which autoantibodies bind to alpha3(IV) collagen in GBM causing rapidly progressive glomerulonephritis and pulmonary hemorrhage. The conformational GP epitopes have been mapped to 2 regions within the noncollagenous (NC1) domain of the alpha3(IV) chain. Recently, we described the molecular organization of the autoantigen in the native alpha3alpha4alpha5(IV) collagen network of the GBM. The crystal structure of the NC1 domain has revealed how the GP epitopes are sequestered in the native GBM. Further insight into the pathogenesis of disease has been obtained from better animal models. These advances provide a foundation for the development of new specific therapies.

ANCA and anti-GBM antibodies in diagnosis and follow-up of vasculitic disease

In the last decade, serological detection of anti-neutrophil cytoplasmic antibodies (ANCA) and of anti-glomerular basement membrane (GBM) antibodies has tremendously facilitated the diagnosis of small vessel vasculitides. Once diagnosed, these diseases have proven to be treatable. However, in contrast to anti-GBM disease, ANCA-associated vasculitides are chronic diseases with a high relapse rate. Since morbidity in ANCA-associated vasculitides is dictated by the frequency and severity of relapses, much health benefit would be achieved if a relapse could be prevented or early treatment started. Increases in ANCA titers and persistently high ANCA levels indicate a high risk of relapse and warrant clinical evaluation of the patient for signs of relapse. This review will focus on the value of ANCA and anti-GBM antibody testing in diagnosis and on the importance of these tests in follow-up of disease.

Serial ANCA titers: useful tool for prevention of relapses in ANCA-associated vasculitis

BACKGROUND

The value of measuring serial antineutrophil cytoplasmic autoantibody (ANCA) titers in guiding therapy among patients with ANCA-associated vasculitis is controversial.

METHODS

We measured serial titers of proteinase 3 (PR3)- and myeloperoxidase (MPO)-ANCA by antigen-specific enzyme-linked immunosorbent assays (ELISAs) in 48 patients with ANCA-associated vasculitis who were followed up during remission at the Massachusetts General Hospital from 1990 through 2000 (mean follow-up, 46.2 months). We retrospectively assessed disease activity by Birmingham Vasculitis Activity Score (BVAS).

RESULTS

We found 21 episodes of fourfold or greater ANCA titer rises in 17 patients who were in complete remission (BVAS=0). Among eight patients who had 10 such titer rises and were not given increased immunosuppression, (group I), all suffered relapses after each episode (mean interval, 5.8 months), whereas among 11 patients, each with one titer rise, who received preemptive increased immunosuppression, (group II), only two relapses occurred, at 3 and 6 months. The difference in the cumulative incidence of relapses in a 1-year period between the two groups was 82% (P=0.0002). Changes in ANCA titers were also used to help guide therapy in the other 31 patients in the study; patients with slight titer rises often received incremental increases in immunosuppression, whereas those with falling titers received incremental decreases. The overall outcome in the entire group was favorable; 46 patients were alive at the end of the study; two died of unrelated diseases.

CONCLUSION

Serial measurements of PR3- and MPO-ANCA titers in patients with ANCA-associated vasculitis during remission can help predict relapses, and preemptive increases in immunosuppression following fourfold titer rises reduces the risk of relapses. Moreover, adjustment of immunosuppression based on lesser titer changes appears to result in a favorable outcome.

Evaluation and treatment of vasculitis in the critically ill patient

The systemic vasculitides, if left untreated, often lead to major organ damage and death. When a patient presents with features that may be consistent with vasculitis, especially with pulmonary and renal findings, it is important to make a specific diagnosis as quickly as possible so that specific therapy can be started. Diagnosis is dependent on familiarity with the myriad of typical and unusual clinical features of the various vasculitides together with performance of supportive tests including serologies, angiograms, and biopsies. When evaluating a potential case of vasculitis, clinicians must comprehensively search for other more common, non-vasculitic diseases. The diagnosis may be even more difficult in patients with established diagnoses of vasculitis on immunosuppressive treatment who develop new clinical findings. Rapid initiation of immunosuppressive therapy for critically ill patients with vasculitis is crucial and may be life-saving.

Diffuse alveolar hemorrhage syndromes

Diffuse alveolar hemorrhage (DAH) is a rare yet serious and frequently life-threatening complication of a variety of conditions. DAH may result from coagulation disorders, inhaled toxins, or infections. Most cases of DAH are caused by capillaritis associated with systemic autoimmune diseases such as antineutrophil cytoplasmic antibodies-associated vasculitis, anti-glomerular basement membrane disease, and systemic lupus erythematosus. Early recognition is crucial, because the prompt institution of supportive measures and immunosuppressive therapy is required for survival. Our understanding of DAH and its management is largely empiric and based on small case series and individual reports, many dating back more than one decade. To provide the practicing specialist with a rational diagnostic and management approach to the patient with DAH, this review summarizes the most recent publications and salient information derived from older publications.

Anti-laminin auto antibodies in ANCA-associated vasculitis

BACKGROUND

Endothelial cell damage occurs during vasculitic processes in vivo. With the alteration of the endothelium, exposure to basement membrane components may occur with induction of humoral immunity.

METHODS

In the present study, we evaluated the prevalence of antibodies against the basement membrane antigen laminin (LMN) in patients with ANCA-associated systemic vasculitis (AASV), pathologic controls (systemic lupus erythematosus, mixed cryoglobulinaemia, Henoch-Schönlein purpura, primary glomerulonephritis) and normal individuals.

RESULTS

By ELISA, 21.6% of AASV (16/74) and 10% of pathologic controls (3/30), but only one of the normal controls (2. 8%) had these antibodies (P=0.02). When AASV patients were divided into two groups according to diagnosis and ANCA antigen specificity, antibodies to LMN were found in 27.5% of MPO-ANCA positive microscopic polyangiitis patients (11/40) vs. only 14.7% of PR3-ANCA positive Wegener granulomatosis patients (5/34). There was no correlation between the presence or titre of anti-LMN antibodies and the main clinical and laboratory parameters.

CONCLUSION

These results indicate that basement membrane antigens may become immunogenic in patients with AASV, especially in those with MPO-ANCA positivity. These antibodies are most likely the result of endothelial damage secondary to the initial inflammatory process but may well perpetuate further vascular damage in some patients.

Sequential development of pulmonary hemorrhage with MPO-ANCA complicating anti-glomerular basement membrane antibody-mediated glomerulonephritis

We report a case of rapidly progressive glomerulonephritis caused by anti-glomerular basement membrane (anti-GBM) antibodies that progressed to end-stage renal disease in a 67-year-old woman with diabetes. Intensive combined immunosuppressive therapy with methylprednisolone bolus, oral prednisone, and cyclophosphamide led to negativity of anti-GBM antibodies but was not able to restore renal function. After 28 months of hemodialysis, the patient suddenly presented with pulmonary hemorrhage. In this setting, high levels of myeloperoxidase (MPO)-antineutrophil cytoplasmic antibody (ANCA) and negative anti-GBM antibodies were found. Therapy with oral prednisone and cyclophosphamide led to resolution of pulmonary hemorrhage and negativity of MPO-ANCA.

Is Wegener's granulomatosis an autoimmune disease?

Wegener's granulomatosis is a multisystem disease characterized by granulomata of the respiratory tract and systemic necrotising vasculitis. There is a strong and specific association with autoantibodies directed against proteinase 3, a constituent of neutrophril azurophilic granules. Antibody titers correlate with clinical disease activity and predict relapses. The disease responds favorably to immunosuppressive therapy. The pathogenicity of antineutrophil cytoplasmic antibodies (ANCA), however, remains unproven. In vitro, the expression of proteinase-3 and other ANCA antigens on the surface of neutrophils and monocytes can be induced by priming with proinflammatory cytokines. Antineutrophil cytoplasmic antibodies are then able to activate these leukocytes, stimulating degranulation, the production of reactive oxygen species, and the secretion of further cytokines. Neutrophils activated by ANCA, and possibly ANCA alone, directly damage endothelial cells in vitro. An animal model of proteinase 3-ANCA-induced vasculitis has not been found. Antineutrophil cytoplasmic antibodies directed against another antigen, myeloperoxidase, are not sufficient to cause vasculitis but they promote damage in certain animal models. Thus, a considerable amount of evidence supports the notion that Wegener's granulomatosis is an autoimmune disease.

Polycystin-1, the PKD1 gene product, is in a complex containing E-cadherin and the catenins

Autosomal dominant polycystic kidney disease (ADPKD) is a common human genetic disease characterized by cyst formation in kidney tubules and other ductular epithelia. Cells lining the cysts have abnormalities in cell proliferation and cell polarity. The majority of ADPKD cases are caused by mutations in the PKD1 gene, which codes for polycystin-1, a large integral membrane protein of unknown function that is expressed on the plasma membrane of renal tubular epithelial cells in fetal kidneys. Because signaling from cell-cell and cell-matrix adhesion complexes regulates cell proliferation and polarity, we speculated that polycystin-1 might interact with these complexes. We show here that polycystin-1 colocalized with the cell adhesion molecules E-cadherin and alpha-, beta-, and gamma-catenin. Polycystin-1 coprecipitated with these proteins and comigrated with them on sucrose density gradients, but it did not colocalize, coprecipitate, or comigrate with focal adhesion kinase, a component of the focal adhesion. We conclude that polycystin-1 is in a complex containing E-cadherin and alpha-, beta-, and gamma-catenin. These observations raise the question of whether the defects in cell proliferation and cell polarity observed in ADPKD are mediated by E-cadherin or the catenins.

What is new with anti-neutrophil cytoplasmic antibodies: diagnostic, pathogenetic and therapeutic implications

Anti-neutrophil cytoplasmic antibodies, as detected by indirect immunofluorescence, have limited diagnostic significance as they occur in a variety of inflammatory disorders. The presence of antibodies to defined target antigens of anti-neutrophil cytoplasmic antibodies, that is proteinase 3 and myeloperoxidase, is, however, highly specific for one of the systemic vasculitides, in particular Wegener's granulomatosis, microscopic polyangiitis, Churg-Strauss syndrome, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis. In general, anti-proteinase-3-positive patients show more widespread organ involvement, more granuloma formation, and a more severe initial course of their renal lesions than anti-myeloperoxidase-positive patients; however, there is considerable overlap, and either antibody specificity may be found in the different clinical syndromes. In vitro, anti-neutrophil cytoplasmic antibodies are able further to activate pre-activated neutrophils and monocytes, which can result in endothelial damage. A direct activating effect of anti-neutrophil cytoplasmic antibodies on endothelial cells has been suggested, but those studies should be confirmed. In vivo, experimental data support a pathogenetic role for anti-neutrophil cytoplasmic antibodies, particularly anti-myeloperoxidase, but besides anti-neutrophil cytoplasmic antibodies a second pro-inflammatory stimulus seems to be required to induce lesions. Whether anti-neutrophil cytoplasmic antibodies can be a direct target for treatment has still to be proved. Current immunosuppressive treatment regimens for the anti-neutrophil cytoplasmic antibody-associated vasculitides are, however, unsatisfactory because of side-effects, that is opportunistic infections and malignancies. New treatment regimens, based on new pathogenetic concepts, are currently being tested.

New insights into polycystic kidney disease and its treatment

Major advances in the understanding of the genetics and pathogenesis of autosomal dominant polycystic kidney disease have occurred within the past year. The proteins encoded by the PKD1 and PKD2 genes, polycystin 1 and polycystin 2, are membrane proteins, capable of interacting physically in vitro, and are likely components of a complex signalling pathway. The majority of PKD1 and PKD2 mutations so far identified are unique inactivating mutations dispersed over the entire genes. Immunohistochemical studies have shown that polycystin 1 and polycystin 2 are developmentally regulated and are overexpressed in polycystic kidneys. The cysts probably result from clonal expansions of single cells. The demonstration of loss of heterozygosity for PKD1 and the absence of immunoreactive polycystin 1 in approximately 20% of the cysts supports a two-hit tumor suppressor gene model of cystogenesis. Regardless of the nature of the initial pathogenic mechanism, the cysts in autosomal dominant polycystic kidney disease are accompanied by partial dedifferentiation of the epithelial cells, disregulation of epithelial cell proliferation, expression of a secretory phenotype, and disarray of cell matrix interactions which leads to interstitial inflammation and matrix accumulation. Recent observations in animal models of inherited polycystic kidney disease have implicated oxidative stress in its pathogenesis. These downstream pathogenetic events have been targeted for intervention, and an increasing number of studies have demonstrated that the course of polycystic kidney disease in rodents can be altered by environmental and pharmacological interventions. Nevertheless, these experimental observations cannot be extrapolated to human autosomal dominant polycystic kidney disease. The recent generation of mice with PKD1 or PKD2 targeted mutations will help to bridge this gap.