Anti-glomerular basement membrane (GBM)-antibody-mediated disease with normal renal function

Atypical Anti-Glomerular Basement Membrane Nephritis: A Case Series From the French Nephropathology Group

RATIONALE & OBJECTIVE

Atypical anti-glomerular basement membrane (GBM) nephritis is characterized by a bright linear immunoglobulin staining along the GBM by immunofluorescence without a diffuse crescentic glomerulonephritis nor serum anti-GBM antibodies by conventional enzyme-linked immunosorbent assay (ELISA). We characterized a series of patients with atypical anti-GBM disease.

STUDY DESIGN

Case series.

SETTING & PARTICIPANTS

Patients identified by the French Nephropathology Group as having atypical anti-GBM nephritis between 2003 and 2022.

FINDINGS

Among 38 potential cases, 25 were included, of whom 14 (56%) were female and 23 (92%) had hematuria. The median serum creatinine at diagnosis was 150 (IQR, 102-203) μmol/L and median urine protein-creatinine ratio (UPCR) was 2.4 (IQR, 1.3-5.2) g/g. Nine patients (36%) had endocapillary proliferative glomerulonephritis (GN), 4 (16%) had mesangial proliferative GN, 4 (16%) had membranoproliferative GN, 2 (8%) had pure and focal crescentic GN, 1 (4%) had focal segmental glomerulosclerosis, and 5 had glomeruli that were unremarkable on histopathology. Nine patients (36%) had crescents, involving a median of 9% of glomeruli. Bright linear staining for IgG was seen in 22 cases (88%) and for IgA in 3 cases (12%). The 9 patients (38%) who had a monotypic staining pattern tended to be older with less proteinuria and rarely had crescents. Kidney survival rate at 1 year was 83% and did not appear to be associated with the light chain restriction.

LIMITATIONS

Retrospective case series with a limited number of biopsies including electron microscopy.

CONCLUSIONS

Compared with typical anti-GBM disease, atypical anti-GBM nephritis frequently presents with an endocapillary or mesangial proliferative glomerulonephritis pattern and appears to have a slower disease progression. Further studies are needed to fully characterize its pathophysiology and associated clinical outcomes.

PLAIN-LANGUAGE SUMMARY

Atypical anti-glomerular basement membrane (GBM) nephritis is characterized histologically by bright linear immunoglobulin staining along the GBM without diffuse crescentic glomerulonephritis or circulating anti-GBM antibodies. We report a case series of 25 atypical cases of anti-GBM nephritis in collaboration with the French Nephropathology Group. Compared with typical anti-GBM disease, we observed a slower disease progression. Patients frequently presented with heavy proteinuria and commonly had evidence of endocapillary or mesangial proliferative glomerulonephritis. About half of the patients displayed a monotypic immune staining pattern; they tended to be older, with less proteinuria, and commonly without glomerular crescents in biopsy specimens. No concomitant circulating monoclonal gammopathy was detected. Further studies are needed to fully characterize its pathophysiology and associated clinical outcomes.

Atypical Anti-Glomerular Basement Membrane Disease

Atypical anti-glomerular basement membrane (anti-GBM) disease is characterized by linear immunoglobulin G (IgG) deposition along the GBM without circulating IgG anti-GBM antibodies. Compared to classic anti-GBM disease, atypical anti-GBM disease tends to be milder with a more indolent course in certain cases. Moreover, pathologic disease pattern is much more heterogenous in atypical anti-GBM disease than in the classic type, which is uniformly characterized by diffuse crescentic and necrotizing glomerulonephritis. Although there is no single well-established target antigen in atypical anti-GBM disease, the target antigen (within the GBM) and the autoantibody type are hypothesized to be different from the classic type. Some patients have the same antigen as the Goodpasture antigen that are detected only by a highly sensitive technique (biosensor analysis). Some cases of atypical anti-GBM disease have autoantibodies of a different subclass restriction like IgG4, or of monoclonal nature. Antibodies targeting antigen/epitope structure other than the Goodpasture antigen can be detected using modified assays in some cases. Patients with IgA- and IgM-mediated anti-GBM disease are known to have negative circulating antibodies because conventional assays do not detect these classes of antibodies. A significant proportion of cases with atypical anti-GBM disease do not have any identifiable antibodies despite extensive evaluation. Nevertheless, extensive evaluation of atypical autoantibodies using modified assays and sensitive techniques should be attempted, if feasible. This review summarizes the recent literature on atypical anti-GBM disease.

Epidemiology, Impact, and Management Strategies of Anti-Glomerular Basement Membrane Disease

Anti-glomerular basement membrane (anti-GBM) disease is a rare but serious autoimmune disease, which is characterized by the development of pathogenic antibodies to type IV collagen antigens in the glomerular and alveolar basement membranes. This results in rapidly progressive glomerulonephritis (GN), alveolar hemorrhage, or both. A variety of environmental factors can trigger the disease in genetically predisposed patients. Temporal associations with influenza, SARS-CoV-2 infection, and COVID-19 vaccination have been described although there is insufficient evidence to suggest causality. Anti-GBM disease accounts for approximately 20% of the cases of rapidly progressive GN cases secondary to crescentic GN, but is an uncommon cause of end-stage kidney disease. Early diagnosis by detection of circulating antibodies, increased awareness of atypical as well as complex clinical variants of the disease, and combined therapy with immunosuppression and plasma exchange has improved the prognosis of patients with this potentially fatal disease. Progress has been hampered by the rarity of anti-GBM disease, but new agents and therapeutic regimens are emerging.

Retinal drusen are more common and larger in SLE with renal impairment

Introduction

Complement has been implicated in systemic lupus erythematosus (SLE) pathogenesis on the basis of the associations with inherited complement defects and genome-wide association study risk alleles, glomerular deposits, reduced serum levels, and occasional reports of retinal drusen. This study examined drusen in SLE and their clinical significance.

Methods

This cross-sectional observational study compared individuals with SLE recruited from renal and rheumatology clinics with hospital controls. Participants were reviewed for clinical features and underwent imaging with a nonmydriatic retinal camera. Deidentified images were examined by 2 trained graders for drusen number and size using a grid overlay.

Results

The cohort with SLE (n = 65) comprised 55 women (85%) and 10 men (15%) with a median age of 47 years (interquartile range 35–59), where 23 (35%) were of southern European or Asian ancestry, and 32 (49%) had biopsy-proven lupus nephritis. Individuals with SLE had higher mean drusen numbers than controls (27 ± 60, 3 ± 9, respectively, P = 0.001), more drusen counts ≥10 (31, 48% and 3, 5%, respectively, P < 0.001), and more medium-large drusen (14, 22% and 3, 5%, respectively, P < 0.001). In SLE, mean drusen counts were higher, and drusen were larger, with an estimated glomerular filtration rate (eGFR) <90 ml/min per 1.73 m² (P = 0.02, P = 0.02, respectively) or class IV nephritis (P = 0.03, P = 0.02).

Conclusion

Drusen composition resembles that of glomerular immune deposits. CFH controls complement activation in the extracellular matrix and CFH risk variants are shared by drusen in macular degeneration and by SLE. CFH represents a possible treatment target for SLE especially with renal impairment.

Double-Positive Anti-GBM and ANCA-MPO Vasculitis Presenting With Crescentic Glomerulonephritis

We report the case of a 61-year-old man with rapidly progressing glomerulonephritis (RPGN) due to double-positive anti-neutrophil cytoplasmic antibodies (ANCA) and anti-glomerular basement membrane antibodies (GBM) vasculitis. The past medical history included stable untreated psoriatic arthritis and arterial hypertension. He presented with asthenia, anorexia, and rapidly deteriorating renal function with metabolic acidosis and hyperkalemia evolving with the need for hemodialysis. No nephrotoxic drugs were identified. Urinalysis showed proteinuria, erythrocyturia, and mild leukocyturia with no pathological casts and renal ultrasound excluded obstruction as the cause of the acute kidney injury. The subsequent study established the diagnosis of double-positive ANCA and anti-GBM vasculitis with renal biopsy confirming the presence of crescentic glomerulonephritis. The patient was started on corticosteroids, cyclophosphamide, and plasmapheresis with the improvement of symptoms and decrease of antibody titers. The renal function recovery was not obtained and referral for transplantation is ongoing.

Etiological Spectrum and Clinical Features in 215 Patients of Crescentic Glomerulonephritis: Is it Different in India?

INTRODUCTION

Crescentic glomerulonephritis (CrGN) characterized by the presence of crescents in most (≥50%) glomeruli on renal histology clinically presents as rapidly progressive renal failure. It can occur due to diverse etiologies with varying course and renal outcomes. We studied the prognostic significance of its classification as pauci-immune, anti-GBM, and immune-complex mediated CrGN.

MATERIALS AND METHODS

Renal biopsies diagnosed as CrGN over 9 years were included. Clinical, biochemical, serological, and histological features of various classes of CrGN were correlated with renal outcome.

RESULTS

215 biopsies were diagnosed as CrGN during this period. A majority (63%) were immune-complex mediated while 32% were pauci-immune, followed by anti-GBM disease (5%). 85.5% of pauci-immune CrGN were ANCA associated. The levels of proteinuria and serum creatinine were significantly higher in anti-GBM CrGN as compared to the other two classes. The various histological features including Bowman's capsule rupture, peri-glomerular granulomatous reaction, fibrinoid necrosis, and vasculitis were more common in anti-GBM disease and pauci-immune CrGN. The median renal survival was 6.3, 5.3, 2.1 months in immune-complex mediated, pauci-immune, and anti-GBM CrGN, respectively.

CONCLUSION

Immune-complex mediated is the commonest etiology of CrGN in India. Anti-GBM disease has the worst prognosis followed by pauci-immune and immune-complex mediated CrGN. Raised serum creatinine levels (>5mg%) and the degree of glomerulosclerosis at diagnosis were predictors of poor renal survival. High index of suspicion and prompt diagnosis can improve the outcome in these patients.

A novel soluble complement receptor 1 fragment with enhanced therapeutic potential

Human complement receptor 1 (HuCR1) is a pivotal regulator of complement activity, acting on all three complement pathways as a membrane-bound receptor of C3b/C4b, C3/C5 convertase decay accelerator, and cofactor for factor I-mediated cleavage of C3b and C4b. In this study, we sought to identify a minimal soluble fragment of HuCR1, which retains the complement regulatory activity of the wildtype protein. To this end, we generated recombinant, soluble, and truncated versions of HuCR1 and compared their ability to inhibit complement activation in vitro using multiple assays. A soluble form of HuCR1, truncated at amino acid 1392 and designated CSL040, was found to be a more potent inhibitor than all other truncation variants tested. CSL040 retained its affinity to both C3b and C4b as well as its cleavage and decay acceleration activity and was found to be stable under a range of buffer conditions. Pharmacokinetic studies in mice demonstrated that the level of sialylation is a major determinant of CSL040 clearance in vivo. CSL040 also showed an improved pharmacokinetic profile compared with the full extracellular domain of HuCR1. The in vivo effects of CSL040 on acute complement-mediated kidney damage were tested in an attenuated passive antiglomerular basement membrane antibody-induced glomerulonephritis model. In this model, CSL040 at 20 and 60 mg/kg significantly attenuated kidney damage at 24 h, with significant reductions in cellular infiltrates and urine albumin, consistent with protection from kidney damage. CSL040 thus represents a potential therapeutic candidate for the treatment of complement-mediated disorders.

Clinicopathological features and outcome of antibody-negative anti-glomerular basement membrane disease

AIM

To explore the clinicopathological characteristics of patients with anti-GBM antibody-negative anti-GBM disease.

METHODS

The clinical and renal pathological findings were retrospectively studied in 19 patients. All patients met the following inclusion criteria: linear GBM IgG deposition on immunofluorescence(IF); and lack of serum anti-GBM antibodies by ELISA and indirect immunofluorescence assay.

RESULTS

There were 17 male and two female patients, with a median age of 36 years (range 15-61 years). Hypertension was present in 68% of cases, nephrotic-range proteinuria (> 3.5 g/24 hours) in 42%, nephrotic syndrome in 37%, microhaematuria in 95%, renal insufficiency in 63% and lung involvement in 16%. On biopsy all patients had linear GBM staining for polyclonal IgG by IF. The dominant IgG subtype was IgG4 or IgG1. By light microscopy, mesangial proliferative GN without crescents was seen in four patients; proliferative GN (mesangial proliferative GN in eight; endocapillary proliferative GN in two; and membranoproliferative GN in two) with crescents (focal in 11; diffuse in one) in 12 patients; and crescentic GN without mesangial or endocapillary proliferative or membranoproliferative changes in three patients. By electron microscopy, six patients showed scarce electron dense deposits in glomeruli and 11 patients had global podocyte effacement. Totally, 10 (53%) patients received immunosuppressive therapy. The median follow-up was 15 months and six (32%) patients progressed to end-stage renal disease.

CONCLUSIONS

Anti-GBM antibody-negative anti-GBM disease was different from classic anti-GBM disease clinically and pathologically. The pathogenesis of the renal injury in these patients has not been elucidated until now and it should be studied and identified further.

A Case of Anti-Glomerular Basement Membrane Antibody-Positive Systemic Lupus Erythematosus with Pulmonary Hemorrhage Successfully Treated at an Early Stage of the Disease

We report here a case of systemic lupus erythematosus (SLE) with pulmonary hemorrhage and anti-glomerular basement membrane (anti-GBM) antibodies. A 42-year-old woman was admitted to our hospital with complaints of exanthema, arthralgia, shortness of breath, and hemoptysis. Plain chest computed tomography (CT) scan revealed pericardial effusion, bilateral pleural effusions, and pulmonary hemorrhage. Laboratory findings on admission revealed proteinuria, microscopic hematuria, anemia, leukopenia, hypoalbuminemia, hypocomplementemia, and slightly elevated levels of serum creatinine. Serological tests revealed elevated titers of serum anti-GBM antibodies, proteinase 3-antineutrophil cytoplasmic antibodies (PR3-ANCA), and anti-double stranded deoxyribonucleic acid (dsDNA)-immunoglobulin G (IgG) antibodies. Early treatment with steroid pulse therapy combined with plasma exchange resolved the patient's pulmonary hemorrhage and renal dysfunction. Renal biopsy carried out after the treatment revealed a recovery phase of acute tubular injury with minor glomerular abnormalities without linear IgG deposition along the GBMs. For a good prognosis, it is necessary to start treatment immediately in patients with anti-GBM antibody-positive SLE associated with pulmonary hemorrhage.

Goodpasture's autoimmune disease - A collagen IV disorder

Goodpasture's (GP) disease is an autoimmune disorder characterized by the deposition of pathogenic autoantibodies in basement membranes of kidney and lung eliciting rapidly progressive glomerulonephritis and pulmonary hemorrhage. The principal autoantigen is the α345 network of collagen IV, which expression is restricted to target tissues. Recent discoveries include a key role of chloride and bromide for network assembly, a novel posttranslational modification of the antigen, a sulfilimine bond that crosslinks the antigen, and the mechanistic role of HLA in genetic susceptibility and resistance to GP disease. These advances provide further insights into molecular mechanisms of initiation and progression of GP disease and serve as a basis for developing of novel diagnostic tools and therapies for treatment of Goodpasture's disease.

18F-FDG PET/CT Imaging of Necrotizing Crescentic Glomerulonephritis With Anti-Glomerular Basement Membrane Disease

A 30-year-old woman presented with lethargy, night sweats, and fever with raised inflammatory markers. Anti-neutrophil cytoplasmic antibody was negative. Abdominopelvic CT was unremarkable. Subsequently, she underwent FDG PET/CT showing globally enlarged kidneys with diffuse hypermetabolic activity within the renal parenchyma bilaterally. Renal biopsies showed morphologic features of an active necrotizing crescentic glomerulonephritis, which was confirmed clinically and treated. This case demonstrates the role that FDG PET/CT can play in inflammatory conditions, such as glomerulonephritis, where it may be clinically useful when the presentation is atypical.

Goodpasture's syndrome in early pregnancy: A case report

Goodpasture's syndrome (GPS) presenting during pregnancy is extremely rare and patients exhibiting hemoptysis and renal dysfunction in early pregnancy are uncommon. The present study reports the case of a 17-year-old diagnosed with GPS during the thirteenth week of pregnancy. Prompt recognition and immediate treatment (steroids and plasma exchange) was initiated. Renal function normalized following treatment and anti-GBM antibody became negative during hospital stay. However, due to irregular follow-up, the patient eventually succumbed. The case highlights that the current treatment plan for GPS should be revised to improve the outcome of pregnancy. In addition, it determines how important it is for obstetricians to consider whether a pregnancy should be terminated to improve the chances of survival of pregnant patients with GPS.

Goodpasture's Syndrome with Negative Anti-glomerular Basement Membrane Antibodies

A young male patient with rapidly progressive and life-threatening pulmonary haemorrhage due to anti-glomerular basement membrane (anti-GBM) antibody disease without renal involvement repeatedly tested negative for serum anti-GBM antibodies. Although rare, anti-GBM antibody disease should be considered in the differential diagnosis in patients with life-threatening pulmonary haemorrhage due to isolated diffuse alveolar haemorrhage. Enzyme-linked-immunosorbent assay (ELISA) testing for anti-GBM antibodies in anti-GBM antibody disease can give false-negative results. A negative serum anti-GBM antibody test is therefore insufficient to exclude the diagnosis. Thus, a kidney or lung biopsy should be considered in any case with a high clinical suspicion but negative anti-GBM antibody test to confirm or rule out the diagnosis.

LEARNING POINTS

Diffuse alveolar haemorrhage (DAH) is a life-threatening disorder caused by severe damage due to injury or inflammation of the alveolar-capillary basement membrane.Anti-GBM antibody disease is a rare autoimmune disorder with circulating autoantibodies directed against the alpha-3 chain[Q2] of type VI collagen of the glomerular and/or alveolar basement membrane which may result in oliguric acute kidney failure due to rapidly progressive glomerulonephritis with or without DAH (commonly referred to as Goodpasture's syndrome).A kidney or lung biopsy should be considered to confirm or rule out the diagnosis if there is a high clinical suspicion but the anti-GBM antibody test is negative; prompt diagnosis and initiation of plasmapheresis, cyclophosphamide and prednisone therapy is essential.

The clinicopathologic characteristics and outcome of atypical anti-glomerular basement membrane nephritis

Classic anti-glomerular basement membrane (GBM) disease presents with rapidly progressive glomerulonephritis (GN) with or without pulmonary hemorrhage. On biopsy typical disease displays bright polytypic linear GBM staining for IgG by immunofluorescence and diffuse crescentic/necrotizing GN on light microscopy. Here, we studied 20 patients with atypical anti-GBM nephritis typified by bright linear GBM staining for immunoglobulins but without a diffuse crescentic phenotype. Patients had hematuria, proteinuria, and mild renal insufficiency, without pulmonary hemorrhage. Light microscopy showed endocapillary proliferative GN in 9 patients, mesangial proliferative GN in 6, membranoproliferative GN in 3, and focal segmental glomerulosclerosis with mesangial hypercellularity in 2. Eight of the 20 showed features of microangiopathy. Crescents/necrosis were absent in 12 and were focal in 8 patients. Bright linear GBM staining for IgG was seen in 17 patients, IgM in 2, and IgA in 1 patient, which was polytypic in 10 patients and monotypic in 10 patients. No circulating α3NC1 antibodies were detected by commercial ELISA. The 1-year patient and renal survival rates were 93% and 85%, respectively. Thus, atypical anti-GBM nephritis is a rare variant of anti-GBM disease characterized clinically by an indolent course, no pulmonary involvement, and undetectable circulating α3NC1 antibodies. Further studies are needed to characterize the molecular architecture of GBM autoantigens in these patients and establish optimal therapy.

Basement membranes and autoimmune diseases

Basement membrane components are targets of autoimmune attack in diverse diseases that destroy kidneys, lungs, skin, mucous membranes, joints, and other organs in man. Epitopes on collagen and laminin, in particular, are targeted by autoantibodies and T cells in anti-glomerular basement membrane glomerulonephritis, Goodpasture's disease, rheumatoid arthritis, post-lung transplant bronchiolitis obliterans syndrome, and multiple autoimmune dermatoses. This review examines major diseases linked to basement membrane autoreactivity, with a focus on investigations in patients and animal models that advance our understanding of disease pathogenesis. Autoimmunity to glomerular basement membrane type IV is discussed in depth as a prototypic organ-specific autoimmune disease yielding novel insights into the complexity of anti-basement membrane immunity and the roles of genetic and environmental susceptibility.

Anti-glomerular basement membrane crescentic glomerulonephritis: A report from India and review of literature

Anti-glomerular basement membrane (anti-GBM) disease is an autoimmune disease that most commonly presents as rapidly progressive glomerulonephritis with or without pulmonary involvement. It is characterized by the presence of antibodies directed to antigenic targets within glomerular and alveolar basement membranes. This study was performed to evaluate the clinicopathological features and outcome in anti-GBM crescentic glomerulonephritis (CrGN) at a tertiary care center in North India over a period of 9 years (January 2004 to December 2012). A diagnosis of anti-GBM CrGN was made in the presence of >50% crescents, linear deposits of IgG along GBM, and raised serum anti-GBM antibody titer. Of 215 cases of CrGN diagnosed during this period, 11 had anti-GBM CrGN. Anti-GBM CrGN was found at all ages but was most common in the third to fifth decade with no gender predilection (mean age 48 +/- 15 years, 13–67 years). Patients presented with a mean serum creatinine of 10.2 +/- 5.3 mg/dl and sub-nephrotic proteinuria. Pulmonary involvement was present in two patients. Myeloperoxidase-antineutrophil cytoplasmic antibody was positive in two (2/11) elderly patients. Follow-up was available in four patients for a range of 30-270 (mean 99.5 ± 114.5) days, two remained dialysis dependent while two died due to uremia and sepsis. Our findings show that anti-GBM disease is a rare cause of CrGN in India, accounting for only 5% of patients. It usually presents as a renal-limited disease and is associated with a poor renal outcome.

Atypical anti-glomerular basement membrane disease

Background

Anti-glomerular basement membrane (anti-GBM) disease classically presents with aggressive necrotizing and crescentic glomerulonephritis, often with pulmonary hemorrhage. The pathologic hallmark is linear staining of GBMs for deposited immunoglobulin G (IgG), usually accompanied by serum autoantibodies to the collagen IV alpha-3 constituents of GBMs.

Methods

Renal pathology files were searched for cases with linear anti-GBM to identify cases with atypical or indolent course. Histopathology, laboratory studies, treatment and outcome of those cases was reviewed in detail.

Results

Five anti-GBM cases with atypical clinicopathologic features were identified (accounting for ∼8% of anti-GBM cases in our laboratory). Kidney biopsies showed minimal glomerular changes by light microscopy; one patient had monoclonal IgG deposits in an allograft (likely recurrent). Three patients did not have detectable serum anti-GBM by conventional assays. Three patients had indolent clinical courses after immunosuppressive treatment. One patient, untreated after presenting with brief mild hematuria, re-presented after a short interval with necrotizing and crescentic glomerulonephritis.

Conclusions

Thorough clinicopathologic characterization and close follow-up of patients with findings of atypical anti-GBM on renal biopsy are needed. Review of the literature reveals only rare well-documented atypical anti-GBM cases to date, only one of which progressed to end-stage kidney disease.

Case report: anti-glomerular basement membrane antibody disease with normal renal function

Background

Anti-glomerular basement membrane (GBM) antibody disease is a rare autoimmune disorder characterized by rapidly progressive glomerulonephritis caused by autoantibodies against the α3-chain of type IV collagen in the GBM.

Case presentation

An 8-year-old girl with hematuria and proteinuria due to anti-GBM nephritis was diagnosed with hematuria and proteinuria during a school urine screening program. Her blood pressure and serum creatinine levels were normal. Her hematuria and proteinuria persisted for several months. Since a spot urine protein to creatinine ratio was around 7 g/g Cre, a percutaneous renal biopsy was performed. Immnofluorescent staining demonstrated a linear pattern for immunoglobulin G along the entire GBM. Chest computed tomography was normal. Anti-GBM antibody assays were reported as slightly raised; thus, the diagnosis was anti-GBM disease with normal renal function. Treatment included plasma exchange, intravenous high-dose methylprednisolone, and cyclophosphamide as a mainstay medication. The treatment was rapidly effective with an immediate decrease in anti-GBM titers and proteinuria.

Conclusions

Cases of anti-GBM disease with normal renal function in children are rare. Treatment in children has not been established; therefore, clinicians need to carefully select an effective treatment because the prognosis is poor.

Necrotizing and crescentic glomerulonephritis presenting with preserved renal function in patients with underlying multisystem autoimmune disease: a retrospective case series

Objective. Necrotizing and crescentic GN usually presents with rapidly declining renal function, often in association with multisystem autoimmune disease, with a poor outcome if left untreated. We aimed to describe the features of patients who have presented with these histopathological findings but minimal disturbance of renal function.

Methods. We conducted a retrospective review (1995–2011) of all adult patients with native renal biopsy–proven necrotizing or crescentic GN and normal serum creatinine (<120 μmol/l) at our centre.

Results. Thirty-eight patients were identified. The median creatinine at presentation was 84 μmol/l and the median proportion of glomeruli affected by necrosis or crescents was 32%. Clinicopathological diagnoses were ANCA-associated GN (74%), LN (18%), anti-GBM disease (5%) and HScP (3%). Only 18% of cases had pre-existing diagnoses of underlying multisystem autoimmune disease, although the majority (89%) had extra-renal manifestations accompanying the renal diagnosis. All patients received immunosuppression and most had good long-term renal outcomes (median duration of follow-up 50 months), although two progressed to end-stage renal disease within 3 years. We estimate that renal biopsy had an important influence on treatment decisions in 82% of cases.

Conclusion. Necrotizing and crescentic GN may present in patients with no or only minor disturbance of renal function. This often occurs in patients with underlying systemic autoimmune disease; early referral for biopsy may affect management and improve long-term outcomes in these cases.

Monoclonal IgG1κ anti-glomerular basement membrane disease: a case report

We report a case of anti-glomerular basement membrane (anti-GBM) nephritis with indolent course, monoclonal IgG1κ (immunoglobulin G, subclass 1, κ light chain) linear staining of the GBM, and multifocal GBM breaks but without crescents or detectable serum anti-GBM antibody in a patient followed over 9 years. Atypically, anti-GBM nephritis follows an indolent course. A very small fraction of patients with anti-GBM nephritis lack detectable circulating anti-GBM antibodies, and rare reports of monoclonal anti-GBM nephritis exist. We report what is to our knowledge the first case manifesting all 3 of these rare variations. Our patient initially presented with asymptomatic decreased kidney function following an upper respiratory tract infection. He was found to have microhematuria and subnephrotic proteinuria with mild diffuse endocapillary proliferative and exudative glomerulonephritis with linear IgG1κ staining of the GBM. He was treated with an induction regimen of intravenous cyclophosphamide and corticosteroids followed by maintenance monotherapy with mycophenolic acid. Nine years later, repeat kidney biopsy for worsening kidney function after an upper respiratory tract infection showed persistent monoclonal staining of the GBM and acute glomerulonephritis with increased chronicity, including a single fibrocellular crescent. Despite extensive clinical investigations spanning nearly a decade, no circulating anti-GBM antibody or monoclonal protein has been detected. In this case report, we explore the unique features of this monoclonal IgG1κ-associated anti-GBM nephritis.

Proteolysis breaks tolerance toward intact α345(IV) collagen, eliciting novel anti-glomerular basement membrane autoantibodies specific for α345NC1 hexamers

Goodpasture disease is an autoimmune kidney disease mediated by autoantibodies against noncollagenous domain 1 (NC1) monomers of α3(IV) collagen that bind to the glomerular basement membrane (GBM), usually causing rapidly progressive glomerulonephritis (GN). We identified a novel type of human IgG4-restricted anti-GBM autoantibodies associated with mild nonprogressive GN, which specifically targeted α345NC1 hexamers but not α3NC1 monomers. The mechanisms eliciting these anti-GBM autoantibodies were investigated in mouse models recapitulating this phenotype. Wild-type and FcγRIIB(-/-) mice immunized with autologous murine GBM NC1 hexamers produced mouse IgG1-restricted autoantibodies specific for α345NC1 hexamers, which bound to the GBM in vivo but did not cause GN. In these mice, intact collagen IV from murine GBM was not immunogenic. However, in Col4a3(-/-) Alport mice, both intact collagen IV and NC1 hexamers from murine GBM elicited IgG Abs specific for α345NC1 hexamers, which were not subclass restricted. As heterologous Ag in COL4A3-humanized mice, murine GBM NC1 hexamers elicited mouse IgG1, IgG2a, and IgG2b autoantibodies specific for α345NC1 hexamers and induced anti-GBM Ab GN. These findings indicate that tolerance toward autologous intact α345(IV) collagen is established in hosts expressing this Ag, even though autoreactive B cells specific for α345NC1 hexamers are not purged from their repertoire. Proteolysis selectively breaches this tolerance by generating autoimmunogenic α345NC1 hexamers. This provides a mechanism eliciting autoantibodies specific for α345NC1 hexamers, which are restricted to noninflammatory IgG subclasses and are nonnephritogenic. In Alport syndrome, lack of tolerance toward α345(IV) collagen promotes production of alloantibodies to α345NC1 hexamers, including proinflammatory IgG subclasses that mediate posttransplant anti-GBM nephritis.

Cutting edge issues in Goodpasture's disease

Goodpasture's disease, or anti-glomerular basement membrane (anti-GBM) disease, is a systemic autoimmune disorder defined by anti-GBM antibody-mediated damage (mainly immunoglobulin G-1) resulting in progressive crescentic glomerulonephritis and, frequently, diffuse pulmonary alveolar hemorrhage. It may be regarded as a "conformeropathy" where the quaternary structure of the α345NC1 hexamer that constitutes GBM undergoes a conformational change, exposing pathogenic epitopes on the α3 and α5 chains, eliciting a pathogenic autoantibody anti-GBM response. Goodpasture's disease accounts for 20% of all patients presenting with a pulmonary-renal syndrome and may be associated with detectable perinuclear antineutrophil cytoplasmic autoantibody positivity in up to a third of patients. Associated triggers may include tobacco smoking, hydrocarbon solvent exposure, and cocaine abuse. Cough, hemoptysis, and dyspnea with fatigue are the commonest presenting features. It is critical to rapidly distinguish Goodpasture's disease from other causes of pulmonary-renal syndromes such as Wegener's granulomatosis. Early and intensive treatment with plasmapheresis and immunosuppression with systemic corticosteroids pending results of diagnostic testing, and later cyclophosphamide, is often beneficial, with 90% of patients surviving the acute presentation of Goodpasture's disease. The need for hemodialysis on initial presentation, a serum creatinine >5 mg/dL, and 50% to 100% crescents on renal biopsy, portend the necessity of long-term hemodialysis. Further elucidation of the molecular pathobiology of Goodpasture's disease, particularly the regulation of involved antigen-specific T cells, may improve early diagnosis, treatment, and outcomes in this rare but potentially lethal autoimmune disorder.

Anti-glomerular basement membrane disease: outcomes of different therapeutic regimens in a large single-center Chinese cohort study

Anti-glomerular basement membrane (GBM) disease usually presents with rapidly progressive glomerulonephritis accompanied by pulmonary hemorrhage. The low incidence and fulminant course of disease preclude a large randomized controlled study to define the benefits of any given therapy. We conducted a retrospective survey of 221 consecutive patients seen from 1998 to 2008 in our hospital, and report here the patient and renal survival and the risk factors affecting the outcomes. Considering the similar clinical features of the patients, we could compare the effects of 3 different treatment regimens: 1) combination therapy of plasmapheresis and immunosuppression, 2) steroids and cytotoxic agents, and 3) steroids alone.The patient and renal survival rates were 72.7% and 25.0%, respectively, at 1 year after disease presentation. The serum level of anti-GBM antibodies (increased by 20 U/mL; hazard ratio [HR], 1.16; p = 0.009) and the presentation of positive antineutrophil cytoplasmic antibodies (ANCA) (HR, 2.18; p = 0.028) were independent predictors for patient death. The serum creatinine at presentation (doubling from 1.5 mg/dL; HR, 2.07; p < 0.001) was an independent predictor for renal failure.The combination therapy of plasmapheresis plus corticosteroids and cyclophosphamide had an overall beneficial effect on both patient survival (HR for patient mortality, 0.31; p = 0.001) and renal survival (HR for renal failure, 0.60; p = 0.032), particularly patient survival for those with Goodpasture syndrome (HR for patient mortality, 0.29; p = 0.004) and renal survival for those with anti-GBM nephritis with initial serum creatinine over 6.8 mg/dL (HR for renal failure, 0.52; p = 0.014). The treatment with corticosteroids plus cyclophosphamide was found not to improve the renal outcome of disease (p = 0.73). In conclusion, the combination therapy was preferred for patients with anti-GBM disease, especially those with pulmonary hemorrhage or severe renal damage. Early diagnosis was crucial to improving outcomes.

Goodpasture's syndrome with positive C-ANCA and normal renal function: a case report

Introduction

Goodpasture's syndrome consists of a triad of pulmonary hemorrhage, rapidly progressive glomerulonephritis and anti-glomerular basement membrane (anti-GBM) antibodies, either in circulation or fixed to the kidney. The absence of renal manifestations is uncommon. We present a case of biopsy proven anti-GBM antibody disease with normal renal function, mild urinary abnormalities and positive C-antineutrophil cytoplasmic antibody (C-ANCA) serology.

Case presentation

A 44-year-old female was treated for repeated episodes of hemoptysis and one episode of respiratory failure requiring ventilatory support. She had minor urinary abnormalities in the form of microscopic hematuria and non-nephrotic proteinuria. She also had positive C-ANCA. Her lung biopsy showed evidence of intra-alveolar hemorrhage with linear IgG deposits in the basement membrane of the alveolar capillaries. Owing to these lung biopsy findings, a kidney biopsy was carried out, which showed minimal thickening of the glomerular basement membrane and linear IgG and C3 deposits along the capillary walls. Her renal function remained persistently normal.

Conclusion

Goodpasture's syndrome is a rare disease. Even though the classical presentation is that of rapidly progressive glomerulonephritis pulmonary hemorrhage and anti-GBM antibodies in the circulation and kidneys, in rare cases it can present with repeated pulmonary hemorrhage and minor urinary abnormalities. In all cases of repeated pulmonary hemorrhage, the possibility of Goodpasture's syndrome should be considered and investigated further.

[Intra-alveolar haemorrhage without renal damage as the initial presenting feature of Goodpasture's syndrome: case report and review of literature]

Isolated pulmonary involvement in Goodpasture's syndrome is exceptionally described. We report a 36-year-old woman with pulmonary haemorrhage and review 28 additional cases of the literature. In fact, these patients had often mild urine abnormalities and constant glomerular lesions. Antiglomerular basement membrane antibodies testing should be systematically ordered in patients presenting with alveolar haemorrhage. Goodpasture's syndrome without renal abnormality could be an early stage of the disease with a better prognosis.

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.

Oculorenal manifestations in systemic autoimmune diseases

Vasculitides form a heterogeneous group of diseases characterized by blood-vessel inflammation and necrosis. They have a wide spectrum of manifestations because of the involvement of arteries and other vessels of various sizes and locations. Early diagnosis and prompt treatment may decrease the morbidity and mortality associated with these disorders. Examination of the eye and kidney should be performed routinely in those diseases. This article reviews the major types of oculorenal manifestations in systemic autoimmune diseases.

Antibody-mediated glomerulonephritis in mice: the role of endotoxin, complement and genetic background

Antibody-mediated glomerulonephritis in man may be exacerbated by infection and this effect may be mediated by bacterial endotoxin. There is evidence supporting a role for endotoxin in heterologous nephrotoxic nephritis in rats, but the role of endotoxin in this model in mice has not previously been explored. Previous data in mice on the role of complement in this model are conflicting and this may be due to the mixed genetic background of mice used in these studies. We used the model of heterologous nephrotoxic nephritis in mice and explored the role of endotoxin, complement and genetic background. In this study we show a synergy between antibody and endotoxin in causing a neutrophil influx. We also show that C1q-deficient mice have an increased susceptibility to glomerular inflammation but this is seen only on a mixed 129/Sv x C57BL/6 genetic background. On a C57BL/6 background we did not find any differences in disease susceptibility when wildtype, C1q, factor B or factor B/C2 deficient mice were compared. We also demonstrate that C57BL/6 mice are more susceptible to glomerular inflammation than 129/Sv mice. These results show that endotoxin is required in this model in mice, and that complement does not play a major role in glomerular inflammation in C57BL/6 mice. C1q may play a protective role in mixed-strain 129/Sv x C57BL/6 mice, but the data may also be explained by systematic bias in background genes, as there is a large difference in disease susceptibility between C57BL/6 and 129/Sv mice.

Pulmonary-renal syndromes in the intensive care unit

Renal disease associated with pulmonary hemorrhage is seen in a variety of clinical disorders and is a common cause of admission to intensive care units. Recent advances in the understanding of the pathogenesis of these disorders have improved the therapeutic options significantly and have favorably influenced the course of many of these disorders. This article discusses rheumatologic diseases that involve both the kidney and lungs, with emphasis on pathogenesis and therapeutic options. Common pulmonary-renal syndromes including anti-glomerular basement membrane disease and anti-neutrophil cytoplasmic autoantibodies-associated vasculitis.