The existence of a protracted course in crescentic glomerulonephritis

Beyond 2D: A scalable and highly sensitive method for a comprehensive 3D analysis of kidney biopsy tissue

The spatial organization of various cell populations is critical for the major physiological and pathological processes in the kidneys. Most evaluation of these processes typically comes from a conventional 2D tissue cross-section, visualizing a limited amount of cell organization. Therefore, the 2D analysis of kidney biopsy introduces selection bias. The 2D analysis potentially omits key pathological findings outside a 1- to 10-μm thin-sectioned area and lacks information on tissue organization, especially in a particular irregular structure such as crescentic glomeruli. In this study, we introduce an easy-to-use and scalable method for obtaining high-quality images of molecules of interest in a large tissue volume, enabling a comprehensive evaluation of the 3D organization and cellular composition of kidney tissue, especially the glomerular structure. We show that CUBIC and ScaleS clearing protocols could allow a 3D analysis of the kidney tissues in human and animal models of kidney disease. We also demonstrate that the paraffin-embedded human biopsy specimens previously examined via 2D evaluation could be applicable to 3D analysis, showing a potential utilization of this method in kidney biopsy tissue collected in the past. In summary, the 3D analysis of kidney biopsy provides a more comprehensive analysis and a minimized selection bias than 2D tissue analysis. Additionally, this method enables a quantitative evaluation of particular kidney structures and their surrounding tissues, with the potential utilization from basic science investigation to applied diagnostics in nephrology.

Clinico-Pathological Outcomes of Patients With Crescentic Glomerulonephritis: A Single-Center Study

Background Crescentic glomerulonephritis (CrGN) is a pathological description of rapidly progressive glomerulonephritis (RPGN). It is characterized by renal failure and is associated with a grave prognosis. This study aimed to investigate the clinical outcomes of patients diagnosed with crescentic glomerulonephritis at the King Abdulaziz University Hospital (KAUH) in Jeddah, Saudi Arabia. Method This retrospective study included patients with CrGN who underwent treatment at the nephrology department at KAUH from June 2021 to August 2022. We collected and analyzed data from 56 patients diagnosed with CrGN on the basis of renal biopsies between 2002 and 2015. Result The study included 17 cases of CrGN. The mean age of patients at the time of diagnosis was 18.06 ± 13.49 years. The distribution of histological findings showed that cellular crescents (94.1%) and interstitial fibrosis and tubular atrophy (IFTA) (76.5%) were the most commonly observed histological findings. The most common underlying etiology was lupus nephritis (41.2%). Regarding the lab results, the mean serum creatinine level at admission was 378.88 ± 273.27 μmol/L, proteinuria was 1.53 ± 1.23 and glomerular filtration rate (GFR) level was 36.94 ± 45.08 mL/min. The factors associated with poor renal outcome were IFTA (P=0.01), phosphate level before discharge, serum creatinine level before and after discharge (P=0.032), and GFR level after discharge (P=0.001). Conclusion Crescentic glomerulonephritis is an important cause of acute kidney injury due to its potential to result in severe glomerular injury. In our study, 12 out of 17 patients experienced poor renal outcomes, which were associated with a high risk of morbidity and mortality. Therefore, early detection and treatment of CrGN is crucial in order to manage the disease.

Demographic, clinical and laboratory characteristics of rapidly progressive glomerulonephritis in Turkey: Turkish Society of Nephrology-Glomerular Diseases (TSN-GOLD) Working Group

BACKGROUND

In our study, diagnostic and demographic characteristics of patients diagnosed with RPGN by biopsy, clinical and laboratory findings in our country were investigated.

METHODS

Data were obtained from the Turkish Society of Nephrology Glomerular Diseases (TSN-GOLD) Working Group database. Demographic characteristics, indications for biopsy, diagnosis of the glomerular diseases, comorbidities, laboratory and biopsy findings of all patients were recorded. According to their types, RPGN patients were classified as type 1 (anti-GBM related), type 2 (immuncomplex related) and type 3 (pauci-immune).

RESULTS

Of 3875 patients, 200 patients with RPGN (mean age 47.9 ± 16.7 years) were included in the study which constitutes 5.2% of the total glomerulonephritis database. Renal biopsy was performed in 147 (73.5%) patients due to nephritic syndrome. ANCA positivity was found in 121 (60.5%) patients. Type 1 RPGN was detected in 11 (5.5%), type 2 RPGN in 42 (21%) and type 3 RPGN in 147 (73.5%) patients. Median serum creatinine was 3.4 (1.9-5.7) mg/dl, glomerular filtration rate was 18 (10-37) ml/min/1.73m² and proteinuria 2100 (1229-3526) mg/day. The number of crescentic glomeruli ratio was ratio 52.7%. It was observed that urea and creatinine increased and calcium and hemoglobin decreased with increasing crescentic glomerular ratio.

CONCLUSIONS

Our data are generally compatible with the literature. Advanced chronic histopathological findings were prominent in the biopsy of 21 patients. Early biopsy should be performed to confirm the diagnosis of RPGN and to avoid unnecessary intensive immunosuppressive therapy. In addition to the treatments applied, detailed data, including patient and renal survival, are needed.

Crescentic glomerulonephritis in children

BACKGROUND

To date, there is insufficient knowledge about crescentic glomerulonephritis (cGN), the most frequent immunologic cause of acute kidney injury in children.

METHODS

Over a period of 16 years, we retrospectively analyzed kidney biopsy results, the clinical course, and laboratory data in 60 pediatric patients diagnosed with cGN.

RESULTS

The underlying diseases were immune complex GN (n = 45/60, 75%), including IgA nephropathy (n = 19/45, 42%), lupus nephritis (n = 10/45, 22%), Henoch-Schoenlein purpura nephritis (n = 7/45, 16%) and post-infectious GN (n = 7/45, 16%), ANCA-associated pauci-immune GN (n = 10/60, 17%), and anti-glomerular basement-membrane GN (n = 1/60, 2%). Patient CKD stages at time of diagnosis and at a median of 362 days (range 237-425) were CKD I: n = 13/n = 29, CKD II: n = 15/n = 9, CKD III: n = 16/n = 7, CKD IV: n = 3/n = 3, CKD V: n = 13/n = 5. Course of cGN was different according to class of cGN, duration of disease from first clinical signs to diagnosis of cGN by biopsy, percentage of crescentic glomeruli, amount of tubular atrophy/interstitial fibrosis and necrosis on renal biopsy, gender, age, nephrotic syndrome, arterial hypertension, dialysis at presentation, and relapse. Forty-eight/60 children were treated with ≥ 5 (methyl-) prednisolone pulses and 53 patients received oral prednis(ol)one in combination with mycophenolate mofetil (n = 20), cyclosporine A (n = 20), and/or cyclophosphamide (n = 6), rituximab (n = 5), azathioprine (n = 2), tacrolimus (n = 1), and plasmapheresis/immunoadsorption (n = 5).

CONCLUSIONS

The treatment success of cGN is dependent on early diagnosis and aggressive therapy, as well as on the percentage of crescentic glomeruli on renal biopsy and on the underlying type of cGN. CsA and MMF seem to be effective alternatives to cyclophosphamide.

Prognostic factors in glomerular diseases with crescents

INTRODUCTION

More than 50% of glomerular crescent formation is required for a diagnosis of crescentic glomerulonephritis in a kidney biopsy. Although treatment protocols have been established for diffuse crescentic glomerulonephritis, there is no standard treatment for patients with fewer crescents in renal biopsies. In this study the importance of crescent percentage and clinical features on renal survival independent of underlying disease was investigated.

METHODS

This retrospective observational study was conducted between 2013 and 2017. Forty-nine patients with crescent formation in their kidney biopsies were evaluated. We compared clinicopathological features and renal survival. We evaluated the factors affecting the course of end stage renal disease (ESRD).

RESULTS

A total of 49 patients (57% male and median age 49 years) were enrolled in this study. 39% of patients developed ESRD at follow-up. Logistic regression analysis showed that the requirement for renal replacement treatment on admission (p < 0.001), serum creatinine level above 2.7 mg/dL (p < 0.001), the presence of more than 50% glomerulosclerosis (p = 0.04) and more than 34% crescent formation (p = 0.002) were significantly associated with ESRD. Kaplan-Meier survival analysis revealed that patients with less than 34% crescent in kidney biopsy and a serum creatinine level less than 2.7 mg/dL had increased kidney survival (log-rank test p: 0.01 and p: 0.002).

CONCLUSION

Patients with crescent formation in kidney biopsy more than 34% should be evaluated for more aggressive treatment modalities regardless of the underlying disease, especially if the serum creatinine level is above 2.7 mg/dL.

Methimazole-Induced Pauci-Immune Glomerulonephritis and Anti-Phospholipid Syndrome: An Important Association to Be Aware of

While methimazole (MMI) is the first line treatment for hyperthyroidism, this medication is not devoid of adverse effects. In this article, we present a 70-year-old male who admitted the hospital with right lower extremity pain and rash. The patient was recently treated with MMI for hyperthyroidism. Imaging studies revealed bilateral renal and splenic infarcts along with thrombosis of popliteal artery. Laboratory data revealed hematuria and proteinuria with positive (MPO), anti-proteinase-3 (PR3) and anti-cardiolipin IgG antibodies. Renal biopsy revealed pauci-immune glomerulonephritis and features with anti-phospholipid antibody syndrome (APS). MMI was discontinued and the patient was treated successfully with steroid therapy and anti-coagulation with resolution of proteinuria, hematuria and normalization of laboratory parameters. While MMI-induced pauci-immune glomerulonephritis has been previously reported, its association with APS has never been described before. Our case demonstrates that this rare diagnosis can be treated by early withdrawal of MMI and initiation of steroids along with anticoagulation.

Renal Involvement in Antineutrophil Cytoplasmic Antibody-Associated Vasculitis

Antineutrophil cytoplasmic antibody-associated vasculitis (AAV) is the most common cause of rapidly progressive glomerulonephritis. ANCAs play an important role in the pathogenesis and diagnosis of AAV. The classic renal lesion in AAV is a pauci-immune necrotizing and crescentic glomerulonephritis. Treatment is divided into 2 phases: (1) induction of remission to eliminate disease activity and (2) maintenance of remission to prevent disease relapse. AAV patients with end-stage renal disease require modification of immunosuppressive strategies and consideration for kidney transplantation. An improved understanding of disease pathogenesis has led to new treatment strategies being tested in clinical trials.

Assessment of the etiologies and renal outcomes of rapidly progressive glomerulonephritis in pediatric patients at King Abdulaziz University Hospital, Jeddah, Saudi Arabia

Objectives:

To investigate the etiologies and outcomes of rapidly progressive glomerulonephritis (RPGN) in pediatric patients at King Abdulaziz University Hospital (KAUH) in Jeddah, Saudi Arabia.

Methods:

A retrospective study was conducted in 19 pediatric patients who were diagnosed with RPGN between 2006 and 2016 at the Department of Pediatric Medicine at KAUH. Associations between variables were evaluated using independent t-test, one-way analysis of variance (ANOVA) and Chi-squared tests.

Results:

Majority of patients were male, (68.4%), with a mean±SD age at diagnosis of 8.52±3.15 years. The most common underlying etiologies were post-infectious glomerulonephritis (PIGN) (63.2%) and lupus nephritis (21.1%). Thirteen patients exhibited a good clinical prognosis (68.4%), with 6 exhibiting a poor prognosis (31.6%), 4 of whom progressed to end-stage renal disease (ESRD), one experiencing a relapse and one developing chronic kidney disease. Post-infectious glomerulonephritis was associated with the best clinical outcome overall. Treatment was implemented early in most patients and continued for 3 months. Among the 19 patients, 2 died and one underwent hemodialysis.

Conclusion:

Post-infectious glomerulonephritis was the most common etiology of RPGN, with these patients achieving a good clinical prognosis overall. Early identification and treatment of RPGN is important to preserve renal function, which is a key factor for achieving a good prognosis.

Combination Therapy With Rituximab and Cyclophosphamide for Remission Induction in ANCA Vasculitis

Introduction

Remission induction in antineutrophil cytoplasmic autoantibody (ANCA) vasculitis may be complicated by slow response to treatment and toxicity from glucocorticoids. We describe outcomes with a novel remission induction regimen combining rituximab with a short course of low-dose, oral cyclophosphamide and an accelerated prednisone taper.

Methods

Patients were included in this retrospective study if they had newly diagnosed or relapsing ANCA vasculitis with a Birmingham Vasculitis Activity Score for Wegener Granulomatosis (BVAS-WG) ≥3 and received a standardized remission induction regimen. The primary outcome was complete remission, defined as a BVAS-WG of 0 and a prednisone dose of ≤7.5 mg/d.

Results

We identified 129 patients who met the inclusion criteria, 31% of whom also received plasma exchange (PLEX) for rapidly progressive glomerulonephritis (RPGN) or diffuse alveolar hemorrhage. Seventy percent of patients had myeloperoxidase (MPO)-ANCA and 9% had relapsing disease. Median time to complete remission was 4 months (interquartile range [IQR] 3.9–4.4), and by 5 months 84% of patients were in complete remission. Prednisone was tapered to discontinuation as tolerated, such that the median prednisone dose at 8 months was 0 mg/d (IQR 0–2.5). In patients with RPGN, proteinase 3–ANCA was associated with a greater increase in eGFR at 6 months compared with MPO-ANCA (16 vs. 5.6 ml/min per 1.73m²; P = 0.028). During the year following remission, 1 major relapse occurred over 122 patient-years. Serious infections occurred more frequently in patients receiving PLEX and were associated with increasing age and diffuse alveolar hemorrhage. Four deaths occurred, 3 of which were associated with serious infections.

Conclusion

Combination therapy was efficacious, allowed for rapid tapering of high-dose glucocorticoids and was well tolerated.

Post-infectious glomerulonephritis with crescents in adults: a retrospective study

Background

Crescent formation generally reflects severe glomerular injury. There is sparse literature on post-infectious glomerulonephritis (PIGN) with crescents in adults. This retrospective study looked at nine such cases to see if there is a correlation between the severity of presentation, steroid treatment, histological severity and outcome.

Methods

Biopsy reports of all the adults who underwent kidney biopsy from February 2010 to June 2014 in a tertiary care hospital were screened and all the cases with the diagnosis of PIGN with crescents were selected. Clinical presentation, laboratory data, histology, treatment and outcome were analysed.

Results

Six patients had evidence of recent/current infection, but all except two were non-streptococcal. The mean creatinine was 360.67 μmol/L (range 70.72–770.85) and the mean estimated glomerular filtration rate (MDRD eGFR) was 30.28 mL/min/1.73 m² (range 6.4–111.1) on presentation. All five patients who were treated with steroids had an excellent response. Among the four patients who did not receive steroids, two were left with significant renal impairment (mean MDRD eGFR 23.5 mL/min/1.73 m²) at a mean follow-up of 15.5 months (range 10–21). The mean percentage of glomeruli with crescents was 36.13% (range 11.76–100) and except in one, there was no tubular atrophy or interstitial fibrosis and none had glomerulosclerosis. None of the patients progressed to end-stage renal disease.

Conclusion

Non-streptococcal infections are more common precipitants. There was no correlation between histological and clinical severity. Patients treated with steroids had better renal outcomes.

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.

Poor Renal Outcome of Antineutrophil Cytoplasmic Antibody Negative Pauci-immune Glomerulonephritis in Taiwanese

BACKGROUND/PURPOSE

Pauci-immune glomerulonephritis (GN) is an important cause of crescentic GN, acute renal failure and mortality. However, data are limited on the clinical presentation and outcome in antineutrophil cytoplasmic antibody (ANCA) negative patients, especially in Asians.

METHODS

This retrospective study analyzed medical records and pathology slides of patients who received renal biopsy between February 1998 and October 2004. Enzyme-linked immunosorbent assay was used routinely for ANCA testing in all patients.

RESULTS

Among 637 patients with biopsy-proven GN included in this study, 88 (13.8%) had glomerular crescent formation. Among them, pauci-immune crescentic glomerulonephritis (PICGN) (42 patients, 47.2%) and lupus nephritis (25 patients, 28.4%) were the most common pathologic diagnoses. Lupus patients were younger (p = 0.028), while PICGN patients had more chronic lesions (p < 0.001), extensive glomerular crescents (p < 0.001), less severe proteinuria (p < 0.001) and poorer renal survival (p = 0.0017). Among the PICGN patients, 62.5% had a positive ANCA test, 80% had myeloperoxidase-ANCA and 20% had proteinase-3-ANCA. Subgroup analysis showed that ANCA negativity was associated with less crescent formation (p < 0.001) but more chronic glomerular lesions (p < 0.001) and a trend toward worse renal outcome (p = 0.055).

CONCLUSION

This study illustrates the necessity for pathologic diagnosis of pauci-immune GN despite ANCA negativity. The poor prognosis associated with ANCA negativity in this study may be partly due to delayed diagnosis since these patients frequently lacked systemic involvement.

[Rapidly progressive glomerulonephritis:classification, pathogenesis and clinical management]

Rapidly progressive glomerulonephritides (RPGN) belong to a heterogeneous group of inflammatory kidney diseases which are commonly associated with systemic vasculitic syndromes. Renal histology is characterized by necrotizing lesions within the glomerual tuft and extracapillary proliferation, in most cases leading rapidly to renal failure. The etiology and pathogenesis are only partly elucidated. Since irreversible renal scaring develops within days to weeks, RPGN represent a nephrological emergency necessitating urgent diagnostic evaluation and rapid institution of effective therapy. New onset nephritic sediment combined with concomitantly deteriorating excretory renal function should lead to immediate nephrological consultation. Autoimmune serology and particularly renal biopsy are of the utmost importance for rapid diagnosis. Most forms of RPGN are treated with immunosuppressive regimens which generally consist of high dose steroids in combination with the alkylating agent cyclophosphamide. Some forms also require the use of plasma exchange therapy. Rapid diagnosis and early therapy improves both renal and overall outcome in the affected patients.

Spontaneous and protracted partial remission of microscopic polyangiitis

Microscopic polyangiitis (MPA), or microscopic polyarteritis, is an idiopathic small vessel vasculitis that frequently causes glomerular damage and renal failure and skin and lung damage in many cases. The renal lesions include focal necrotizing glomerulonephritis, extracapillary proliferative (crescentic) glomerulonephritis, and tubulointerstitial infiltration with polymorphonuclear leukocytes and lymphocytes. MPA often is associated with the presence of antineutrophil cytoplasmic autoantibody (ANCA) (myeloperoxidase positive) as a diagnostic marker. MPA commonly is regarded as a serious condition that places the survival of the kidneys and the patient at risk. Typically, there is a prodrome of some weeks to months, with rapid decline in renal function and dialysis as a potential outcome if intensive immunosuppressive treatment is not given or is delayed. We describe an otherwise typical case of MPA occurring in a 52-year-old woman presenting with multisystem disease, antimyeloperoxidase ANCA antibodies, renal impairment, and necrotizing crescentic glomerulonephritis in whom this usual sequence of events was not followed because the patient refused steadfastly to have any treatment for nearly a decade. Renal function remained stable for nearly 10 years, although there were persistent proteinuria, microscopic hematuria, and antimyeloperoxidase ANCA antibodies. A late renal-pulmonary relapse occurred, and immunosuppression was permitted only briefly. Prolonged renal and patient survival in the absence of immunosuppressive treatment has been reported rarely in this context.

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis

Antiproteinase 3- and antimyeloperoxidase-associated vasculitis. Wegener's granulomatosis, microscopic polyangiitis, and idiopathic pauci-immune necrotizing crescentic glomerulonephritis (NCGN) are strongly associated with antineutrophil cytoplasmic autoantibodies (ANCAs) directed against either proteinase 3 (anti-PR3) or myeloperoxidase (anti-MPO). This has led some investigators to prefer combining these diseases under the common heading of ANCA-associated vasculitides. However, it is increasingly recognized that there are characteristic differences between patients with anti-PR3 and those with anti-MPO-associated vasculitis. This review focuses on the clinical, histopathologic, and possibly pathophysiologic differences between anti-PR3- and anti-MPO-associated vasculitis. Although there is considerable overlap, the anti-PR3- and anti-MPO-associated vasculitides are each characterized by particular clinical and histopathological findings. Extrarenal organ manifestations and respiratory tract granulomas occur more frequently in patients with anti-PR3 than in those with anti-MPO. Anti-PR3-positive patients with NCGN generally have a more dramatic deterioration of their renal function compared with anti-MPO-positive patients. The term "ANCA-associated vasculitis" is considered as a useful concept in the presence of systemic vasculitis. Likewise, in the presence of vasculitis, the terms "anti-PR3-associated vasculitis" and "anti-MPO-associated vasculitis" are useful concepts.

A clinical and pathological study on the characteristics and factors influencing the prognosis of crescentic glomerulonephritis using a cluster analysis

Crescentic glomerulonephritis (CrGN) is expressed by a rapidly progressive lesion. However, there is no unanimous view on the factors that affect the prognosis. We carried out a follow-up study of 109 CrGN patients consisting of 54 males (age 55.3 +/- 15.7) and 55 females (age 54.0 +/- 16.3) by a cluster analysis using pathomorphological parameters at the time of biopsy, and thus found two categories which were significantly different regarding the speed of progress (P = 0.0249). The component factors of rapidly progressive CrGN included a combination of several factors such as: (i) a high frequency of crescents; (ii) frequent sclerosis and hyalinosis in the glomeruli with crescents; (iii) extensive tubulo-interstitial damage (cellular, fibrocellular and fibrous) in the renal cortex; (iv) hyperproteinuria; (v) high mean blood pressure; and (vi) anemia. Thus, the prognosis of CrGN is regulated by no single factor but instead by a complex combination of mutually associated factors.

Fundamental concepts and immunosuppressive treatment in the various forms of glomerulonephritis

Immunosuppressive treatment in glomerulonephritis (GN) is still controversial. Most of the secondary forms of glomerulonephritis have the histologic features of one of the primary types of glomerulonephritis. Eight histologic expressions of primary glomerulonephritis can be distinguished and ordered in terms of severity of symptoms and prognosis: endocapillary GN, minimal change GN, mesangioproliferative GN, membranous GN, focal-sclerosing GN, membranoproliferative GN, focal-necrotizing GN, and rapidly progressive GN. Agreement exists only to the extent that immunosuppression is not required in endocapillary glomerulonephritis, although it is recommended in the other extreme of rapidly progressive GN. Primarily, an indication for immunosuppression is given by the severity of symptoms with a urinary protein excretion > 3.5 g per day and/or serum creatinine > 150 mumol per liter. As for anti-GBM, the type of glomerulonephritis is more important than the severity of symptoms in guiding therapy, whereas for IgA nephropathy it is controversial whether the prospective prognosis of even inexorably deteriorating renal function justifies immunosuppression. Renal biopsy is required to identify the type of glomerulonephritis so as to establish the specific immunosuppressive concept with different intensity and duration of treatment. Immunosuppression can reduce urinary protein excretion and improve deterioration of renal function; however, the proportion of patients responding varies with and depends on the different forms of GN.

Differences between anti-myeloperoxidase- and anti-proteinase 3-associated renal disease

We performed a retrospective study of the clinical features, the pattern of the pre-treatment renal function loss, the renal morphology and the outcome in 92 patients with anti-neutrophil cytoplasmic autoantibodies directed against proteinase 3 (aPR3; N = 46) or myeloperoxidase (aMPO; N = 46). Patients with aMPO had a higher median age than patients with a PR3 (63 and 56 years; P < 0.05). The mean (+/- SD) number of affected organs in the aPR3 group exceeded that of the aMPO group (3.9 +/- 1.4 and 2.2 +/- 1.1; P < 0.01). The prevalence of renal involvement did not differ between patients with aPR3 and aMPO (83% and 67%, respectively; NS). Pre-treatment renal function deteriorated significantly faster in aPR3- than in aMPO-associated renal disease. The kidney biopsies from patients with aPR3 showed a higher activity index (10.2 +/- 3.8 and 7.3 +/- 3.2; P < 0.03) and a lower chronicity index (4.5 +/- 2.6 and 7.0 +/- 3.1; P < 0.02) than biopsies from patients with aMPO. The kidney survival at two years was 73% in patients with aPR3- and 61% in patients with aMPO-associated renal disease (NS). We conclude that renal function generally deteriorates faster in aPR3- than in aMPO-associated renal disease. This goes together with more active renal lesions in patients with aPR3 and more chronic renal lesions in patients with aMPO. Despite these differences, there is no difference in outcomes between both antibody groups.

Rapidly progressive glomerulonephritis (RPGN): is there still an "idiopathic" subgroup?

In order to clarify if "idiopathic" RPGN still exists as a distinct entity we reviewed 41 patients with histological picture of diffuse crescentic GN (60% of crescents) and no clinical evidence of systemic disease. According to the presence or absence of intraglomerular necrotizing lesions we subdivided the patients into two different morphological groups: Group I (25 pts) with necrotizing GN and massive periglomerular infiltrates; Group II (16 pts) with intra-extracapillary proliferation and no interstitial infiltrates. Our data suggest that "idiopathic" RPGN does not exist as a distinct entity, but is an expression either of renal limited vasculitis or crescentic GN complicating primary proliferative GN.

Rapidly progressive glomerulonephritis: classification, pathogenetic mechanisms, and therapy

Immunopathologic studies over the past two decades have demonstrated that rapidly progressive glomerulonephritis (RPGN) can result from glomerular deposition of anti-GBM antibody, immune complexes, or from some as yet undefined mechanism that does not involve glomerular antibody deposition. The latter process may be cell mediated and resembles a small vessel vasculitis. Most cases of idiopathic RPGN are not accompanied by pathogenic glomerular immunoglobulin deposition. Recent experimental studies of immune mechanisms of glomerular injury have identified several new processes that can induce damage to the capillary wall sufficient to result in crescentic glomerulonephritis (GN). These include direct effects of anti-GBM antibody alone and of the complement C5b-9 (membrane attack) complex, nephritogenic effects of inflammatory effector cells that involve reactive oxygen species and glomerular halogenation, and injury mediated by sensitized lymphocytes independently of antibody deposition. Macrophages have been shown to participate in both intracapillary and extracapillary fibrin deposition and crescent formation as well as to mediate capillary wall damage. The role of resident glomerular cells and cell-cell interactions in glomerulonephritis is still under active investigation. Despite these several advances in understanding immune injury to the glomerulus, therapy for RPGN remains largely empiric. Although the prognosis in RPGN has clearly improved over time, no form of disease-specific therapy has been clearly shown yet to be beneficial in a controlled study. Interpretation of the existing literature on therapy is complicated by the availability of only historical rather than concurrent controls, lack of attention to several variables known to affect disease outcome, and uncertainty regarding bias in favor of reporting positive results. Available data suggests that optimal outcomes may be achieved in anti-GBM nephritis by treatment with steroids, immunosuppression and plasma exchange, particularly when therapy is directed at patients with mild but rapidly progressive disease before oliguria or severe azotemia develop. Pulse steroids are probably the most cost-effective therapy for the idiopathic form of RPGN, but treatment with cytotoxic agents should be considered if clinical or histologic evidence of vasculitis is present.