No evidence for a specific role of IgM in mesangial proliferation of idiopathic nephrotic syndrome

IgM deposition is a risk factor for delayed remission and early relapse of the pediatric minimal change disease

BACKGROUND

Minimal change disease (MCD) is the most common pathological subtype of pediatric idiopathic nephrotic syndrome (INS). It has been suggested that IgM deposition might predict kidney function deterioration in the course of MCD. However, the specific role of IgM deposition in the prognosis of MCD is still controversial. This study aims to investigate the clinical significance of IgM deposition on delayed remission and early relapse in a pediatric population.

METHODS

This study enrolled 283 children diagnosed with MCD by renal biopsy in a single center from 2010 to 2022. These cases were divided into two groups according to the histopathological deposition of IgM. Patients' demographics, clinical parameters, and follow-up data were collected and analyzed. The primary and secondary outcomes were defined as the time to the first remission and the first relapse.

RESULTS

The IgM-positive group had a weaker response to steroids (steroid-sensitive: 23.5% vs. 40.8%; steroid-dependent: 74.0% vs. 51.0%; steroid-resistant: 18.4% vs. 8.2%, P = 0.001), and showed more recurrent cases (47.2% vs. 34.4%, P = 0.047) compared with the IgM-negative group. The Kaplan-Meier analysis showed that the IgM-positive group had a lower cumulative rate of the first remission (Log-rank, P < 0.001) and a higher rate of the first relapse (Log-rank, P = 0.034) than the IgM-negative group. Multivariate Cox analysis showed that IgM deposition was independently associated with the delayed first remission (hazard ratio [HR] = 0.604, 95% confidence interval [CI] = 0.465-0.785, P < 0.001) and the early first relapse (HR = 1.593, 95% CI = 1.033-2.456, P = 0.035).

CONCLUSION

IgM deposition was associated with a weaker steroid response. MCD children with IgM deposition were prone to delayed first remission and early first relapse.

Clinical characteristics and outcomes of idiopathic membranous nephropathy with glomerular IgM deposits

Glomerular IgM deposition is commonly shown in idiopathic membranous nephropathy, but the clinicopathological features and outcomes of IMN with IgM deposition are unclear. This single-center prospective cohort study enrolled 210 patients with biopsy-proven IMN from January 2016 to December 2018. Clinicopathological features, treatment responses, and kidney outcomes were compared between patients with and without IgM deposition. In total, 76 (36.2%) patients show glomerular IgM deposition. Patients with IgM deposition were younger (45 ± 13.30 vs. 50.59 ± 13.65 years, P = 0.006), had a higher estimated glomerular filtration rate (eGFR) (100.03 [81.31-111.37] vs. 92.67 [74.71-106.63] mL/min/1.73 m², P = 0.041), and had a lower proportion of nephrotic syndrome (60.5% vs. 75.4%, P = 0.024) at the time of kidney biopsy. Patients with IgM deposition had a significantly higher proportion of focal segmental glomerular sclerosis (FSGS) lesions (27.6% vs. 13.4%, P = 0.011) and C1q deposition (72.4% vs. 57.5%, P = 0.032). Although the treatments and initial treatment responses were comparable, patients with glomerular IgM deposition had a significantly greater proportion of eGFR decline of ≥ 5 mL/min/1.73 m² per year (log-rank test, P < 0.001) and eGFR decrease of ≥ 10% from baseline (log-rank test, P = 0.003). Cox regression analysis showed that IgM deposition was an independent risk factor of eGFR decline of ≥ 5 mL/min/1.73 m² per year (HR, 2.442; 95% CI, 1.550-3.848, P < 0.001) and eGFR decline by ≥ 10% from baseline (HR, 2.629; 95% CI, 1.578-4.385, P < 0.001) during follow-up. IgM deposition in the glomeruli is an independent risk factor for decreased renal function in patients with IMN.

Renal Outcome of IgM Nephropathy: A Comparative Prospective Cohort Study

Immunoglobulin M nephropathy (IgMN) is an idiopathic glomerulonephritis characterized by diffuse deposits of IgM in the glomerular mesangium. However, its renal prognosis remains unknown. We compared renal outcomes of IgMN patients with those of patients with minimal change disease (MCD), focal segmental glomerulosclerosis (FSGS), or mesangial proliferative glomerulonephritis (MsPGN) from a prospective observational cohort, with 1791 patients undergoing native kidney biopsy in eight hospitals affiliated with The Catholic University of Korea between December 2014 and October 2020. IgMN had more mesangial proliferation and matrix expansion than MsPGN and more tubular atrophy and interstitial fibrosis than MCD. IgMN patients had decreased eGFR than MCD patients in the earlier follow-up. However, there was no significant difference in urine protein or eGFR among all patients at the last follow-up. When IgMN was divided into three subtypes, patients with FSGS-like IgMN tended to have lower eGFR than those with MCD-like or MsPGN-like IgMN but higher proteinuria than MsPGN-like IgMN without showing a significant difference. The presence of hypertension at the time of kidney biopsy predicted ≥20% decline of eGFR over two years in IgMN patients. Our data indicate that IgMN would have a clinical course and renal prognosis similar to MCD, FSGS, and MsPGN.

IgM mesangial deposition as a risk factor for relapses of adult-onset minimal change disease

BACKGROUND

Immunoglobulin M (IgM) mesangial deposition in pediatric minimal change disease (MCD) has been reported to be associated with steroid dependence and poor renal outcomes. However, the evidence linking the impacts of IgM mesangial deposition to the treatment prognosis in adult-onset MCD is still elusive.

METHODS

In this retrospective cohort study, 37 adult patients with MCD received kidney biopsies from January 2010 to May 2020. Immunofluorescence microscopy was performed and the patients dichotomized according to IgM mesangial deposition (12 patients with positive IgM deposition; 25 patients with negative IgM deposition). We analyzed the clinical features, the dosage of immunosuppressive agents, and the response to treatment for 2 years between the two groups.

RESULTS

Analysis of the clinical symptoms, the dosage of immunosuppressive treatment, and the time to remission revealed no statistical difference between the groups. However, compared to the negative IgM group, the frequency of relapses was significantly higher in the positive IgM group during the two-year follow-up period (the negative IgM group 0.25 episodes/year; the positive IgM group 0.75 episodes/year, p = 0.029). Furthermore, multivariate linear regression revealed that the positivity of IgM mesangial deposition is independently associated with the frequency of relapses (regression coefficient B 0.450, 95% CI 0.116-0.784, p = 0.010).

CONCLUSIONS

Our findings indicated that adult-onset MCD patients with IgM mesangial deposition have a high risk of relapses. Therefore, intensive monitoring of disease activity should be considered in MCD adults with IgM mesangial deposition.

The natural history of immunoglobulin M nephropathy in adults

Background

Immunoglobulin M (IgM) nephropathy is an idiopathic glomerulonephritis characterized by diffuse mesangial deposition of IgM. IgM nephropathy has been a controversial diagnosis since it was first reported, and there are few data identifying specific pathological features that predict the risk of progression of renal disease.

Methods

We identified 57 cases of IgM nephropathy among 3220 adults undergoing renal biopsy at our institution. Biopsies had to satisfy the following three criteria to meet the definition of IgM nephropathy in this study: (i) dominant mesangial staining for IgM, (ii) mesangial deposits on electron microscopy (EM) and (iii) exclusion of systemic disease.

Results

The median age was 42 years and 24 patients were male. Thirty-nine per cent of patients presented with the nephrotic syndrome, 49% presented with non-nephrotic proteinuria and 39% had eGFR <60 mL/min. The median post-biopsy follow-up was 40 months and serum creatinine had doubled in 31% by 5 years. Of histological parameters, glomerular sclerosis and tubular atrophy, but not mesangial proliferation, were risk factors for renal insufficiency. Thirty-nine per cent of nephrotic patients achieved complete remission, and outcome was significantly worse in those who did not respond to treatment. Focal segmental glomerulosclerosis was diagnosed in 80% of those undergoing repeat renal biopsy, despite ongoing mesangial IgM deposition.

Conclusions

We propose criteria for a consensus definition of IgM nephropathy.

IgM as a novel predictor of disease progression in secondary focal segmental glomerulosclerosis

Aim

To determine the role of immunoglobulin M (IgM) deposits in clinical manifestations, disease outcome, and treatment response of idiopathic and secondary focal segmental glomerulosclerosis (FSGS).

Methods

Kidney biopsy specimens of 171 patients diagnosed with FSGS (primary and secondary) and 50 control patients were retrospectively included in the study. For each patient, clinical and outcome data were obtained and compared to morphological parameters, including immunofluorescence analysis of mesangial IgM and complement 3 (C3) deposits analyzed on kidney biopsy samples.

Results

There were significant positive correlations between IgM and C3 deposition in secondary FSGS (P < 0.001) and between IgM and mesangial deposits detected by electron microscopy in secondary FSGS (P = 0.015), which indicated that higher IgM deposition correlated with higher C3 deposition and mesangial deposits only in secondary FSGS. Patients with secondary FSGS and the deposition of IgM showed inferior renal outcomes at earlier time points in comparison with patients with negative IgM expression (P = 0.022).

Conclusions

We detected a positive correlation between IgM and C3 in secondary FSGS. The association between IgM deposition and worse renal outcome in secondary FSGS indicates that IgM may play a role in the progression of this disease.

IgM nephropathy: is it closer to minimal change disease or to focal segmental glomerulosclerosis?

Immunoglobulin (Ig)M nephropathy (IgMN), known since 1978, is a very controversial clinicopathological entity characterized by IgM diffuse deposits in the mesangium at immunofluorescence whereas light microscop identifies minimal glomerular lesion, hypercellularity and expansion of the mesangium or sclerotic focal, segmental lesion. Clinically, it is a nephrotic syndrome, especially in pediatric patients, or asymptomatic proteinuria and/or isolated hematuria. These characteristics narrowly define IgMN between minimal change disease and focal segmental glomerulosclerosis, so it is not often recognized as a separate pathology. Homogeneous epidemiologic, pathogenetic, clinical or histological data are not available. Recent research on the pathogenetic role of mesangial IgM has, however, renewed interest in IgMN and naturally the controversies.

IgM exacerbates glomerular disease progression in complement-induced glomerulopathy

While glomerular IgM deposition occurs in a variety of glomerular diseases the mechanism of deposition and its clinical significance remain controversial. Some have theorized IgM becomes passively trapped in areas of glomerulosclerosis. However, recent studies found that IgM specifically binds damaged glomeruli. Therefore, we tested whether natural IgM binds to neo-epitopes exposed after insults to the glomerulus and exacerbate disease in mice deficient in the complement regulatory protein factor H; a model of non-sclerotic and nonimmune-complex glomerular disease. Immunofluorescence microscopy demonstrated mesangial and capillary loop deposition of IgM while ultrastructural analysis found IgM deposition on endothelial cells and subendothelial areas. Factor H deficient mice lacking B cells were protected from renal damage, as evidenced by milder histologic lesions on light and electron microscopy. IgM, but not IgG, from wild-type mice bound to cultured murine mesangial cells. Furthermore, injection of purified IgM into mice lacking B cells bound within the glomeruli and induced proteinuria. A monoclonal natural IgM recognizing phospholipids also bound to glomeruli in vivo and induced albuminuria. Thus, our results indicate specific IgM antibodies bind to glomerular epitopes and that IgM contributes to the progression of glomerular damage in this mouse model of non-sclerotic glomerular disease.

IgM nephropathy; time to act

Implication for health policy/practice/research/medical education: Much has been published on the epidemiology and clinicopathological characteristics of IgM nephropathy, but there is little information on the etiology,pathogenesis and specific therapy of the disease. Controversy still shrouds the definition and nosologic status of the disease. Well-coordinated and concerted international efforts and collaboration between researchers in the developing and developed countries are needed to make further progress on the above aspects of the disease.

IgM contributes to glomerular injury in FSGS

Glomerular IgM and C3 deposits frequently accompany idiopathic FSGS and secondary glomerulosclerosis, but it is unknown whether IgM activates complement, possibly contributing to the pathogenesis of these diseases. We hypothesized that IgM natural antibody binds to neoepitopes exposed in the glomerulus after nonimmune insults, triggering activation of the complement system and further injury. We examined the effects of depleting B cells, using three different strategies, on adriamycin-induced glomerulosclerosis. First, we treated wild-type mice with an anti-murine CD20 antibody, which depletes B cells, before disease induction. Second, we evaluated adriamycin-induced glomerulosclerosis in Jh mice, a strain that lacks mature B cells. Third, we locally depleted peritoneal B cells via hypotonic shock before disease induction. All three strategies reduced deposition of IgM in the glomerulus after administration of adriamycin and attenuated the development of albuminuria. Furthermore, we found that glomerular IgM and C3 were detectable in a subset of patients with FSGS; C3 was present as an activation fragment and colocalized with glomerular IgM, suggesting that glomerular IgM may have bound a cognate ligand. Taken together, these results suggest that IgM activates the complement system within the glomerulus in an animal model of glomerulosclerosis. Strategies that reduce IgM natural antibody or that prevent complement activation may slow the progression of glomerulosclerosis.

Is cyclophosphamide effective in patients with IgM-positive minimal change disease?

BACKGROUND

We analyzed the impact of immunoglobulin M (IgM) positivity on the relapse-free interval post completed course of cyclophosphamide (CYC) treatment in patients with steroid-dependent nephrotic syndrome (SDNS) and minimal change disease (MCD).

METHODS

This was a retrospective chart review of all children who received CYC for SDNS and MCD between 1988 and 2009. Patients were divided into three groups based on kidney biopsy: MCD without immunoglobulin M (IgM) positivity (IgM-), MCD with IgM-positive immunofluorescence (IF) only (IgM+), and MCD with IgM-positive IF and electron-dense deposits on electron microscopy (IgM++). The relapse-free time interval to the first relapse post-CYC therapy or up to 48 months of follow-up (if no relapse occurred) was used for survival analysis.

RESULTS

Forty children aged 1.5-12.3 years (15 were IgM-, 16 were IgM+, 9 were IgM++) received a cumulative CYC dose of 175 ± 30 mg/kg. The overall relapse-free survival time was 75 % at 12 months, 64 % at 24 months, 59 % at 36 months, and 56 % at 48 months, with no significant differences between the IgM groups (p = 0.80).

CONCLUSIONS

Based on our results, we conclude that more than 50% of our SDNS patients with MCD remained relapse-free 4 years post-CYC treatment. No significant difference in the response to CYC was observed between patients with or without IgM positivity.

IgM nephropathy revisited

IgM nephropathy (IgMN) is an idiopathic immune complex-mediated glomerulopathy that was first described as a distinct disease in a nephropathology literature in 1978. Here, a historical review and the current status of IgMN in the light of world literature and the current experience will be presented. The Pubmed (www.pubmed.gov) search was made for articles on IgMN as the sole subject of the study or where it constituted a significant number of cases in a biopsy series in the world literature written in English. A total of 41 articles were found. A critical review of the literature was made. Soon after 1978, a series of reports were published mostly from the western world, but the interest in the entity did not withstand the test of time. No substantial basic medical research was carried out and the disease was largely ignored by the western researchers. More recently, a flurry of articles have appeared in the literature on the topic, mostly from tropical countries, and have renewed the interest in the entity. However, most of the current literature on IgMN is based on clinical observations, and experimental models and mechanistic studies of IgMN are lacking. There is an urgent need to develop consensus based criteria for the diagnosis of the condition, as well as, to focus the research on mechanistic studies to understand the pathogenesis of the disease better.

Clinicopathologic characteristics and steroid response of IgM nephropathy in children presenting with idiopathic nephrotic syndrome

There is no detailed information on clinical and immunopathologic features of immunoglobulin M nephropathy (IgMN) in children with idiopathic nephrotic syndrome (INS) in Pakistan. We reviewed our native renal biopsies over 15 years (July 1995-July 2010) and identified 135 cases of IgMN in nephrotic children (≤17 years). Their demographic, clinical and immunopathologic data were retrieved from biopsy reports and case notes. Mean age of this cohort was 7.6 ± 4.2 years. Males were 92 (68.1%) and females were 43 (31.9%). Steroid-dependent NS was seen in 88 (65.2%) cases and steroid-resistant NS in 47 (34.2%). Hematuria was found in 42 cases (31.2%) and hypertension in 27 (19.5%). The most common morphologic change was glomerular mesangial proliferation, found in 89 (65.9%) biopsies. Minor changes were seen in 46 (34.1%) cases and focal segmental glomerulosclerosis (FSGS) in 37 (27.4%). Immunofluorescence microscopy showed diffuse mesangial positivity of IgM in all cases. C3 and C1q were found in 72 (53.3%) and 40 (29.7%) cases, respectively. Our results show that IgMN is a fairly common cause of INS in children in Pakistan. It shows a spectrum of morphologic changes ranging from minor changes to FSGS.

Minimal change disease with IgM+ immunofluorescence: a subtype of nephrotic syndrome

Immunoglobulin (Ig) M nephropathy is defined by electron-dense mesangial deposits and mesangial IgM visible by immunofluorescence (IF) without other histopathologic and immunofluorescent microscopic abnormalities. Certain patients have only immuno-positive (IgM+) IF. Children presenting with steroid-dependent or steroid-resistant nephrotic syndrome have a high prevalence of IgM+ IF with or without electron-dense deposits. We reviewed the clinical course of children with steroid-dependent or steroid-resistant nephrotic syndrome who underwent renal biopsy at Texas Children's Hospital from 1989 to 2006 to further characterize IgM+ IF in children with nephrotic syndrome. Of the 55 children with steroid-resistant or -dependent minimal change disease (MCD), 23 had IgM+ IF. Of these 23 children, 61% had microscopic hematuria at presentation, 48% (11/23) were steroid-dependent, and 48% (11/23) steroid-resistant (one underwent biopsy prior to steroid therapy). We compared the efficacy of adjuvant treatment with cyclophosphamide and cyclosporine: 18% initially treated with cyclophosphamide obtained remission, while 55% had no response; 83% obtained subsequent remission with cyclosporine. Of those initially treated with cyclosporine, 88% obtained complete or partial remission. IgM+ IF may be surrogate marker for the severity of MCD. Based on our results, children with MCD and IgM+ IF have a better response to cyclosporine than cyclophosphamide.

Glomerulopathy with mesangial IgM deposits: long-term follow up of 64 children

BACKGROUND

The aim of the present study was to investigate to what extent IgM nephropathy in children with minimal change nephrotic syndrome (MCNS) and diffuse mesangial hypercellularity (DMH) evolves to focal segmental glomerulosclerosis (FSGS).

METHODS

Tissues from renal biopsies were examined by light microscopy (LM), immunofluorescence (IF) and, in four cases, by electron microscopy (EM). From a total of 352 nephrotic children, 121 had renal biopsy results as steroid dependent or resistant. A diagnostic renal biopsy was also performed in 331 children with non-nephrotic proteinuria and/or hematuria. A second renal biopsy was performed in 16 children whose renal function was impaired during the follow up. The clinical course of IgM-positive children was compared with that of IgM-negative children.

RESULTS

Of the 121 nephrotic children with renal biopsy, 85 were MCNS. Twenty were IF positive mainly for IgM, six of whom (30%) presented evolution to FSGS, while of the remaining 65 IF-negative children, only three (4.6%) presented evolution to FSGS. Of the total 331 children with non-nephrotic proteinuria and/or hematuria, 139 were diagnosed as IgA--IgG nephropathy, 44 had positive IF for IgM and 148 were IF negative. Of the 44 children IF positive for IgM, seven (15.9%) presented evolution to FSGS, while none of the 148 IF-negative children presented evolution to FSGS. The follow-up time for all children ranged from 1 to 14 years.

CONCLUSIONS

Of IgM nephropathy patients with MCNS and DMH, a significant percentage develop impaired renal function, due to the evolution of FSGS, as revealed by repeat biopsy during long-term follow up.

Mesangioproliferative glomerulonephritis with IgM deposition: clinical characteristics and outcome

The significance of IgM on immunofluorescence in renal biopsy specimens remains unclear. This retrospective case study was conducted to define the clinical features, response to therapy and outcome of patients with Mesangioproliferative Glomerulonephritis (MGN) with diffuse IgM deposition. Of 1919 native renal biopsies performed over a ten-year period, 139 (7.2%) had light microscopic features of MGN and manifested IgM as the dominant immunoglobulin. When exclusion criteria (more than a trace of IgA or IgG, segmental IgM, evidence of SLE, vasculitis, FSGS or Alport's syndrome and pregnant patients) were applied, 60 patients (3.1%) remained. Follow-up data were available for 54 cases with a mean age of 26.5 years (range 1.7-63). Mean follow-up period was 7.4 years (range 4.7-22.2). Forty-one per cent presented with nephrotic syndrome (NS), 26% with asymptomatic proteinuria (>250mg/24hr), 18% with macroscopic hematuria and 15% with isolated microscopic hematuria. Twenty-one percent of patients were hypertensive at presentation. Creatinine was initially <120 (mol/L in all but one patient. Only four patients (7.4%), all nephrotic, suffered a decline in renal function despite treatment; all 4 developed ESRF after a mean of 5.6 years (range 2-8.3). Two of these were subsequently re-biopsied and found to have FSGS. No patients with isolated microscopic / macroscopic hematuria or asymptomatic proteinuria suffered a decline in renal function. Protein excretion rate fell into the normal range in 63% of those receiving steroids, with 82% becoming steroid dependent. Of those treated with cyclosporine (48%) or cyclophosphamide (52%) only 9.5% and 14.5% respectively remained in prolonged remission after discontinuing treatment. It is concluded that MGN with IgM deposition carries a very favorable prognosis except in patients with NS who develop FSGS. However there is a high incidence of steroid dependence and resistance in the proteinuric group.

Adult-onset idiopathic nephrotic syndrome associated with pure diffuse mesangial hypercellularity

BACKGROUND

Pure diffuse mesangial hypercellularity (DMH), in its primary form, is a relatively rare histological finding and few data exist in the literature regarding its clinical course and prognosis in nephrotic adults with this diagnosis.

METHODS

We retrospectively analysed the clinical and histological data of 28 adult nephrotic patients (13 male) with this diagnosis with regard to response to the treatment, outcome and prognostic indicators.

RESULTS

Of 25 patients treated with prednisolone (Pred), nine (36%) showed complete remission (CR) of proteinuria, eight (32%) partial remission (PR) and eight (32%) did not respond at all (NR). The combination of cyclosporin treatment with prednisolone of those with PR or NR produced one further complete and two partial remissions. At the end of follow-up (mean 64 months), 10 patients (40%) were in CR, nine (36%) in PR and six (24%) were NR and remained nephrotic. Renal function remained unchanged in patients with CR or PR. In contrast, the six non-responders progressed to end-stage renal disease (ESRD). Compared with non-responders, patients who responded to Pred were older and had normal renal function at presentation. This group also had less mesangial sclerosis and severe tubulointerstitial fibrosis and none showed synechiae with Bowman's capsule. IgM mesangial deposits were observed in 22% of patients with CR in response to Pred, in 37% of those with PR and in 100% of non-responders, who finally progressed to ESRD. A multivariate analysis of clinical and histological features at biopsy showed persistent nephrotic syndrome (P<0.001), the severity of DMH (P<0.03) and the presence of mesangial IgM (P<0. 01) to have independent predictive value for ESRD. This analysis also demonstrated that only mesangial sclerosis (P<0.03) and the presence of mesangial IgM (P<0.002) independently predicted the response to therapy.

CONCLUSIONS

DMH associated with idiopathic nephrotic syndrome is a heterogeneous entity. Patients who respond to therapy (completely or partially) have a benign course similar to that of minimal change nephrotic syndrome. They are usually older and have normal renal function at presentation, whereas 'sclerotic' lesions are less frequent findings in initial biopsies. Non-responders tend to be younger and progress to ESRD. Most of them have impaired renal function at first assessment and more prominent 'sclerotic' lesions on initial biopsies. Mesangial IgM is an independent marker of poorer response to treatment and progression to ESRD but it lacks specificity.

Morphological studies of baseline needle biopsies from living donor kidneys: light microscopic, immunohistochemical and ultrastructural findings

Fifty-seven consecutive living donors (31 women and 26 men aged 20.7-72.3 years, mean 50.6 years) were subjected to needle biopsy during nephrectomy, immediately before removal of the kidney. By light microscopy, semiquantitative scoring (0-3) was performed for arteriosclerosis, arteriolar hyalinosis (hyalin arteriolosclerosis), glomerulosclerosis, interstitial mononuclear cell infiltration, and interstitial fibrosis/tubular atrophy. Whereas vascular changes were striking in many biopsies (arteriosclerosis grades 2-3: 28/54 cases, arteriolar hyalinosis grades 2-3: 15/55 cases), glomerular and tubulointerstitial changes were mostly low grade. The morphological changes tended to be more pronounced in middle-aged and older individuals, but, in particular, vascular changes were seen also in the younger age group. Immunofluorescence microscopy revealed glomerular granular staining for IgM in 52.7% of the cases, IgA in 9.1%), IgG in 1.8%, and C3 in 12.7%. The main ultrastructural finding was glomerulosclerosis; one case with diffuse glomerular IgA showed distinct dense deposits, and one case showed similar dense deposits without IgA deposition. Arteriolar wall deposition of C3 was found in 58.2% of the cases, and IgM in 10.9%. Especially C3 occurred both with arteriolar hyalinosis and in arterioles without light microscopic alterations. The observation of significant vascular changes in baseline biopsies is relevant especially in the differential diagnosis of chronic rejection and cyclosporine nephropathy. The immunohistochemical findings strongly indicate the occurrence of immunoglobulins and complement factor C3 in both glomeruli and arterioles without clinical or morphological signs of renal disease. The possible pathophysiological significance of such deposits remains, however, uncertain.

The nonspecificity of focal segmental glomerulosclerosis. The defining characteristics of primary focal glomerulosclerosis, mesangial proliferation, and minimal change

We performed a detailed clinical review and pathologic analysis of the kidney biopsies of 134 children with nephrotic syndrome or asymptomatic proteinuria. This analysis challenges some of our concepts about the classification of conditions associated with these disorders. The presence of focal segmental sclerotic lesions does not define a unique disorder in childhood. Some children with such lesions will have unaffected glomeruli that are ultrastructurally completely normal. These patients, predominately black adolescents, present either with nephrotic syndrome or asymptomatic proteinuria. We classify this disorder as primary focal segmental glomerulosclerosis (FSGS) and have never found it to recur after transplantation. Most other children with FSGS have 1 of 2 specific glomerulopathies. Those with minimal change have generalized fusion of podocyte foot processes. Those with mesangial proliferation have similar foot process changes combined with mesangial expansion and proliferation and, frequently, thinning of the lamina densa and tubuloreticular inclusions. The presence of segmental lesions in these glomerulopathies appears to be nothing more than a marker of severity. Children with these glomerulopathies are generally younger white children, virtually all of whom have nephrotic syndrome. These disorders have a strong propensity to recur after transplantation. The presence of mesangial labeling of IgM or C1q has no significance in any of these 3 disorders. The classification of disorders associated with nephrotic syndrome or asymptomatic proteinuria must concentrate less on the presence or absence of focal sclerosis and more on the histologic appearance of the rest of the glomeruli.

Outcome of idiopathic childhood nephrotic syndrome. A 20 year experience

112 patients with idiopathic childhood nephrotic syndrome have been referred from 1970 through 1989 at the Department of Pediatrics, University of Berne. One patient remitted spontaneously without medication. Ninety-eight patients responded to prednisone: 15 had a single bout of nephrosis, 47 developed a tendency towards relapses and 36 steroid dependence. In 28 patients with tendency towards relapses cure took place on either prednisone alone or prednisone plus cyclophosphamide. In 18 patients with steroid dependency cure took place on prednisone alone or prednisone plus cyclophosphamide. Thirteen patients failed to respond to steroids. The course of the disease was more benign in 68 patients with minimal change disease as compared with 14 patients with focal and segmental glomerular sclerosis. Immunofluorescence studies demonstrated mesangial IgM deposits in 14 out of 54 patients, but this finding was not a marker for poor steroid response or progression to renal failure. The course of the disease was especially unfavourable in patients with persisting nephrosis on completion of the initial course of steroid therapy. In conclusion it appears appropriate to define the disease in terms of steroid responsiveness as steroid resistant patients sometimes show normal glomeruli, steroid responsive sometimes have focal and segmental glomerular sclerosis or mesangial IgM deposits, and decisions depend more on the steroid responsiveness than on the histological features.

Glomerular lesions in fibrotic kidneys of Norwegian slaughter pigs. Light microscopic and immunohistochemical studies

An abattoir survey of renal lesions in Norwegian slaughter pigs demonstrated the presence of a macroscopic evident nephropathy characterised by pale, slightly enlarged and fibrotic kidneys in 143 out of 668 (21.4%) examined carcasses. At light microscopy fibrotic kidneys revealed glomerular lesions characterised by a diffuse mesangial proliferative glomerulopathy. Immunohistochemical examination demonstrated mesangial and paramesangial immune complex deposition containing IgM and C3, and to a lesser degree IgA and IgG in the glomeruli of fibrotic kidneys. Our observation of glomerular lesions caused by immune complex depositions in fibrotic pig kidneys are compared with mesangial nephropathies in man.

Sustained expression of TGF-beta 1 underlies development of progressive kidney fibrosis

We found that TGF-beta 1 expression and increased matrix production is transient and self-limited in nephritic glomeruli from rats with acute, reversible glomerulonephritis induced by a single injection of an antibody reactive with glomerular mesangial cells. In contrast, in rats given a second antibody injection, one week later, the glomerular expression of TGF-beta 1 mRNA and TGF-beta 1 protein remained elevated through 18 weeks and was associated with a large infiltration of mononuclear cells, with staining features of fibroblastic/myofibroblastic cells, strongly expressing TGF-beta 1 in the tubulointerstitium of the kidney. By 18 weeks kidneys from animals receiving two antibody injections showed glomerulosclerosis and tubulointerstitial fibrosis with striking deposition of collagens type I and III, whereas kidney tissue from animals given one antibody injection was indistinguishable from normal control. The histological changes were accompanied by persistent proteinuria and elevated levels of blood urea nitrogen. Extracellular matrix markers of TGF-beta 1 activity, a special isoform of fibronectin, tenascin, biglycan and plasminogen activator inhibitor-1, were significantly elevated in kidneys undergoing fibrosis. These data suggest that sustained TGF-beta 1 expression contributes to the development of progressive kidney fibrosis.

Mesangial proliferative glomerulonephritis in southwestern American Indians

A series of 166 American Indian renal biopsy specimens from 1971 to 1989 showed a very high proportion with mesangial proliferative glomerulonephritis with mesangial immunoglobulin deposition (Ig-pos mesGN). This disease comprised 68.7% of all the biopsies and 83.8% of all primary GN, proportions much greater than those (23.5% and 37.7%, respectively) of a local contemporaneous biopsy series from non-Indians (P < 0.001). These proportions and the extrapolated population-based incidence rates of mesGN are the highest yet described in any population. Males and females were equally represented in the Indian Ig-pos mesGN series. Biopsy was most commonly performed in early adulthood, but duration of suspected disease prior to biopsy was often many years. Mesangial glomerulonephritis often occurred in family clusters. It was occasionally associated with rashes, arthralgias, and/or a history of alcohol abuse. Due to different surveillance and biopsy practices, the spectrum of severity was different in Zunis and Navajos, allowing examination of clinicopathologic correlations over a broad range of disease. Early disease was manifest by microscopic hematuria alone, but rates of severe disease, with hypertension, heavy proteinuria, and renal insufficiency, were very high. Clinical severity increased with age, with extension of pathology beyond the mesangium, and with scarring and vascular change. Changing patterns of deposition of mesangial immunoglobulin and of electron-dense deposits in sequential biopsy specimens, recurrence of disease in kidney transplants, and biopsy diagnosis of disease in asymptomatic relatives of afflicted subjects were all observed. Five-year renal failure rates were estimated at 41%, much higher than in most other series. This disease constituted most biopsied cases of GN-end stage renal disease in Navajos, and largely determined the young age of Navajo GN-end stage renal disease subjects compared with their US-wide counterparts. To reconcile the diversity of clinical and morphologic findings in such homogeneous ethnic groups, and in individual families within such groups, we propose a unifying hypothesis for a broader spectrum of mesGN than traditionally defined by immunoglobulin subtype deposition. We also argue against a major role for IgA aggregates or immune complexes in initiating or propagating the mesangial inflammatory process, and propose that mesangial pathology of another, independent cause might be primary. Hyperinsulinemia, or insulin resistance, which is common in these populations and in other transitional populations with similar GN and ESRD patterns, might be one such mesangiopathic factor.

Clinicopathological features of childhood nephrotic syndrome in Saudi Arabia

The clinicopathological features are described in 119 Arab children in Saudi Arabia with the nephrotic syndrome. The clinical and laboratory data are similar to those described in other parts of the world. However, mesangial proliferative glomerulonephritis (MesPGN) was found in 21 of 66 biopsies (31.8%), giving a frequency of 17.6% of all children with the nephrotic syndrome. Minimal-change nephrotic syndrome (MCNS) was diagnosed in 17 biopsies (25.8%) and in 58 patients (48.7%). Onset of the nephrotic syndrome was at less than 1 year of age in 17 patients (14.3%). Seven children had 11 episodes of peritonitis. Seven children had positive hepatitis B surface antigen (HBsAg) in their serum: renal biopsy carried out on four of them showed membranous glomerulonephritis (MGN) in three, and four of the seven patients developed end-stage renal disease (ESRD). There were nine deaths, all in patients with end-stage renal disease: six of the deaths occurred in infants. The pattern of childhood nephrotic syndrome in Saudi Arabia is different from the pattern in tropical countries.

Quantitation of antigen in tissue by immunofluorescence image analysis

A method is described to measure antigen(s) in tissue section using an image analysis system to quantitate immunofluorescence following staining with fluorescein isothiocyanate (FITC)-conjugated antibody. The antigen utilized was an 125I-labeled goat anti-glomerular basement membrane antibody (1409 cpm/micrograms) administered intravenously to each of 11 Sprague-Dawley rats in doses ranging from 1.09 to 34.72 mg IgG. 24 h later, both kidneys were obtained for quantitative immunofluorescence following staining of tissue sections with FITC-labeled rabbit anti-goat IgG and for determination of radioactivity which reflects the amount of goat IgG present in isolated glomeruli. A linear correlation (r = 0.97) was observed between the dose of administered goat 125I-IgG and the amount bound to isolated glomeruli over the entire dosage range. A highly significant correlation (r = 0.98) was also seen between the mean brightness per glomerulus as determined by quantitative immunofluorescence and the amount of 125I-IgG bound per glomerulus but only at values less than 500 pg of IgG per glomerulus. Above these levels no correlation was observed, suggesting the presence of hidden epitopes in the bound goat IgG or the lack of availability of the FITC-labeled rabbit antibody.

Immunopathological findings in idiopathic nephrosis: clinical significance of glomerular "immune deposits"

Idiopathic nephrosis (IN), which includes minimal change (MCD), diffuse mesangial proliferation (DMP) and focal segmental glomerular sclerosis (FSGS), is classically characterized by the absence of significant deposits by immunofluorescence microscopy (IF), except for the focal lesions of segmental sclerosis and/or hyalinosis of FSGS, which fix IgM and C3 antiserums. Since IF is available in most centres, an increasing number of unexpected findings has been reported. In order to evaluate the clinical significance of the glomerular deposits revealed by IF in some instances, we reviewed the renal biopsy findings of 222 consecutive children presenting with IN and in whom IF microscopy was available. By light microscopy, 122 patients showed MCD, 10 DMP, and 90 FSGS with DMP (11 cases) or without (79 cases). By IF, 125 specimens were negative and served as controls; 54 showed mesangial IgM deposits, 24 mesangial IgG deposits (associated with Clq deposits in 16), 15 scattered granules of C3 and 4 predominant deposits of mesangial IgA. We correlated these findings with initial response to steroid therapy and outcome and could find no significant difference between the various categories defined by IF and the control group. Repeat biopsies, performed in 21 cases, showed the persistence of deposits in 11 and their transformation in 10. The particular problem raised by the patients who present with IN and mesangial IgA deposits is discussed. Our results demonstrate that patients presenting with IN and "positive IF", whether showing IgM, IgG and Clq, C3 or IgA, do not represent distinct clinicopathological entities.

Treatment of proteinuric idiopathic glomerulonephritides in adults: a retrospective survey

PURPOSE

A review of the worldwide medical literature was undertaken to determine whether treatment with currently available drugs has been beneficial in patients with glomerulonephritides.

MATERIALS AND METHODS

Thirty-five articles, involving 1,653 adult patients with chronic primary glomerulonephritis with proteinuria and/or nephrotic syndrome, were analyzed. The criteria for inclusion of data were strict, and only complete and well-studied cases were included in the analysis. The papers were grouped into prospective controlled trials, retrospective comparisons of treated and untreated patients, and retrospective studies without an untreated group.

RESULTS AND CONCLUSIONS

Analysis of the data shows that patients with minimal change disease clearly benefited from the administration of corticosteroids and/or cytotoxic drugs, since 89 percent and 79 percent of patients had a complete remission in controlled trials and in retrospective studies, respectively. A low incidence of complete and partial remissions was found in the group of patients with focal segmental glomerulosclerosis, proteinuria disappeared in 19 percent, and only 36 percent of these patients had stable renal function after a mean follow-up period of 6.3 years. The incidence of uremia and the number of patients requiring dialysis were very high. In patients with membraneous glomerulonephritis, conflicting results were obtained in controlled trials, retrospective comparisons, and retrospective studies, since a high percentage of complete and partial remissions was present in treated patients from both controlled and retrospective comparisons, whereas the percentage of complete and partial remission in untreated patients increased as the length of the follow-up period increased. Long-term studies carried out on untreated patients confirmed the high percentage of remissions. These data suggest that it is necessary to await future long-term results from controlled trials in order to determine whether or not corticosteroids alone or associated with cytotoxic drugs have a beneficial effect. Finally, the data from patients with mesangiocapillary glomerulonephritis show that therapy appears to have no beneficial effect on renal function. Nephrologists need new drugs that interfere more decisively with the immune process in the pathogenesis of primary glomerulonephritis.

Glomerulonephritis: approaches to classification

Glomerulonephritis has many mechanisms and may take a variety of patterns. Almost as many classifications of glomerulonephritis exist as there have been classifiers. None is perfect. Morphological classification of glomerulonephritis is inadequate alone but provides useful information about the pattern of response to the injurious mechanism and may allow accurate assessment of prognosis. In this paper some approaches to the classification of glomerulonephritis are discussed, the major categories are reviewed and a prognostic method of classification is proposed.

A clinicopathologic study of forty-eight infants with nephrotic syndrome

The clinical and histopathologic features of 48 children presenting with the nephrotic syndrome during the first year of life were analyzed. Proteinuria was discovered soon after birth to 3 months of age in 39 infants (congenital nephrotic syndrome), and nine infants had an infantile onset presenting between 4 and 12 months of age. Neither histologic parameters--microglomeruli, epithelial, or mesangial proliferation, focal segmental or global sclerosis, fibrinoid necrosis, or tubular microcysts--nor histologic classification--microcystic disease, mesangial proliferative glomerulonephritis, focal segmental glomerular sclerosis/hyalinosis-predicted the outcome. Rather, age at presentation was found to predict outcome: One of 39 infants with a congenital onset and seven of nine infants with an infantile onset underwent a complete remission (P less than 0.0001).