Clinical course and outcome of idiopathic membranous nephropathy in Japanese children

Clinical and Histopathologic Characteristics of Pediatric Patients With Primary Membranous Nephropathy

Introduction

Primary membranous nephropathy (PMN) is uncommon in children. Therefore, data on the clinical course of affected children are scarce. In recent years, several novel antigens have been implicated in the pathogenesis of PMN. However, the histopathologic characteristics of pediatric patients with PMN remain poorly represented in the literature.

Methods

We have retrospectively analyzed the clinical presentation and outcomes data of 21 children with PMN from 3 centers in the United States. In addition, we have identified novel antigens in biopsy specimens from these patients and correlated their presence or absence to clinical outcomes. Finally, we compared the results of the novel antigen staining from our clinical cohort to a validation cohort of 127 biopsy specimens from children with PMN at Arkana Laboratories.

Results

The data from the 2 cohorts demonstrated similar overall antigen positivity rates of 62% to 63%, with phospholipase A2 receptor (PLA2R) and exostosin 1 (EXT1) being the most commonly found antigens. Results from the clinical cohort showed that overall, the kidney prognosis for children with PMN was good, with 17 of 21 patients entering a complete or partial remission. Children who were positive for PLA2R or EXT1 were significantly more likely to enter remission than those in the antigen negative group.

Conclusion

Approximately 60% of pediatric membranous cases are positive for a novel antigen on kidney biopsy and the clinical prognosis is generally favorable. More studies are needed to understand the clinical implications of each specific novel antigen.

Nephrotic Syndrome

Nephrotic syndrome is characterized by edema, proteinuria, hypoalbuminemia, and hyperlipidemia. Minimal change disease, the most common cause in childhood, generally responds to corticosteroids, although most patients experience disease relapses. Focal segmental glomerulosclerosis is usually resistant to corticosteroids and carries a significant risk of kidney failure, necessitating renal transplantation. Nephrotic syndrome may also be secondary to gene mutations and systemic diseases such as lupus. Clinical evaluation involves distinguishing primary and secondary causes and monitoring for disease complications, including blood clots and serious infections such as spontaneous bacterial peritonitis. Immunosuppressive medications are used to prevent relapses and treat corticosteroid-resistant disease.

High-density Association Mapping and Interaction Analysis of PLA2R1 and HLA Regions with Idiopathic Membranous Nephropathy in Japanese

Although recent studies showed anti-PLA2R antibody plays a crucial role in idiopathic membranous nephropathy (IMN), detailed HLA mapping and interaction between the HLA genes and PLA2R1 have not been investigated in IMN. We genotyped across the PLA2R1 gene and the HLA region, using 183 IMN patients and 811 healthy controls. Five SNPs around the PLA2R1 gene were significantly associated with IMN. In addition to the two SNPs previously reported to be strongly associated with IMN, rs3749119 and rs35771982 (OR 3.02 and 2.93, P = 3.24E-14 and 4.64E-14, respectively), two novel intronic SNPs (rs2715928 and rs16844715) were also identified as IMN-associated SNPs (OR = 2.30 and 2.51, P = 3.15E-10 and 5.66E-13, respectively). In the HLA gene analysis, DRB1*1501 and DQB1*0602 were strongly associated with IMN (P = 1.14E-11 and 1.25E-11, respectively). The interaction was strongest between HLA-DRB1*15:01 - HLA-DQB1*06:02 and the intronic SNP rs2715928 (OR = 17.53, P = 4.26E-26). Furthermore, positive interaction was also observed between HLA-DRB1*15:01 - HLA-DQB1*06:02 and the missense SNP rs35771982 (OR = 15.91, P = 2.76E-29), which is in strong linkage disequilibrium with 5′UTR SNP rs3749119, and intronic SNP rs16844715 (OR = 15.91, P = 2.30E-26) for IMN. Neither HLA-DRB1*15:01 nor HLA-DQB1*06:02 was associated with steroid responsiveness, overall survival and renal survival during the observation period of mean 11 years though limited number of analysis.

Idiopathic membranous nephropathy in children in China

Idiopathic membranous nephropathy (IMN), which was the result from non-SLE, non-hepatitis B or C virus infection, is relatively rare in children. We collected 584 pediatric cases of renal biopsy specimens in children hospitalized in Xijing Hospital from Jan 2008 to Dec 2013. We found that IgA nephropathy (27.9%) and Henoch-Schönlein purpura (26.4%) are the most common etiology of pediatric kidney disease, followed by minimal change disease (10.4%). Surprisingly, the prevalence of IMN is very high (7.5%) in pediatric patients. Moreover, the prevalence of IMN is quickly increasing from 4.4% in 2009 to 9.1% in 2013.

Coexisting Membranous Nephropathy and IgA Nephropathy

We herein present a case of a 14-year-old boy with the histological features of coexisting membranous nephropathy (MN) and IgA nephropathy (IgAN). Asymptomatic hematuria/proteinuria was initially detected in school urinary screening, with treatments including oral corticosteroids leading to complete remission. Cases of coexisting MN and IgAN are very rare among the pediatric population; however, the overlap of these two nephropathies does not always imply a deleterious clinical outcome in pediatric cases.

Membranous nephropathy: not just a disease for adults

Membranous nephropathy (MN) is an immune complex-mediated cause of the nephrotic syndrome that can occur in all age groups, from infants to the elderly. While systemic disorders such as hepatitis B infection or lupus may more frequently cause secondary MN in the younger population, primary or "idiopathic" MN has generally been considered a disease of adults. Recent progress in our understanding of primary disease was recently made when the target antigen in primary MN was identified as the M-type phospholipase A2 receptor (PLA2R). Circulating anti-PLA2R antibodies may serve both as a diagnostic tool for distinguishing primary from secondary disease and as a biomarker for monitoring the immunologic activity of this organ-specific autoimmune disease during treatment. Whereas definitive therapy for secondary forms of MN should be targeted at the underlying cause, immunosuppressive therapy is often necessary for primary disease. Alkylating agents in combination with corticosteroids, as well as calcineurin inhibitors (± steroids), are first line agents due to randomized controlled trials in an adult population with relatively long durations of follow-up. However, rituximab, mycophenolate and adrenocorticotropic hormone have shown promise in smaller and/or observational studies. The optimal therapy for children and adolescents with MN is less well defined.

Membranous nephropathy in children: clinical presentation and therapeutic approach

The approach to the pediatric patient with membranous nephropathy (MN) can be challenging to the practitioner. The clinical presentation of the child with this histologic entity usually involves some degree of proteinuria ranging from persistent, subnephrotic-ranged proteinuria to overt nephrotic syndrome. Patients often have accompanying microscopic hematuria and may have azotemia or mild hypertension. Children presenting with nephrotic syndrome are often steroid resistant; as such, their biopsy for steroid-resistant nephrotic syndrome results in the diagnosis of MN. The practitioner treating MN in the pediatric patient must weigh the risks of immunosuppressive therapy against the benefits. In general, the child with subnephrotic proteinuria and normal renal function can likely be treated conservatively with angiotensin blockade (angiotensin-converting enzyme inhibitors or angiotensin receptor blockers) without the need for immunosuppressive therapy. Those with nephrotic syndrome are usually treated with steroids initially and often followed by alkylating agents (cyclophosphamide or chlorambucil). Calcineurin inhibitors may also be useful, but the relapse rate after their discontinuation remains high. The absence of controlled studies in children with MN makes treatment recommendations difficult, but until they are available, using the patient's clinical presentation and risk of disease progression appears to be the most prudent approach.

Membranous glomerulonephritis: treatment response and outcome in children

The aim of this study was to characterize clinical features, treatment response, and outcome of idiopathic membranous glomerulonephritis (MGN) in a single-center cohort of children. A retrospective review of biopsy-proven idiopathic MGN in 12 children (mean age 11.9 years) was undertaken. Presentation was nephrotic syndrome (NS) (75%), hematuria/proteinuria (17%), and asymptomatic proteinuria (8%). Ten patients (83%) with NS and nephrotic range proteinuria (NRP) were treated with prednisone, and two patients with non-NRP were not treated with immunosuppressive medications. Steroid response in the treated patients was complete (10%), partial (40%), and absent (50%), respectively. Oral cyclophosphamide was used in seven patients of whom five were steroid resistant, one was steroid dependent, and one was partially responsive. At the mean follow up of 27 months, outcome parameters included an estimated glomerular filtration rate of 128 cc/min per 1.73 m(2), albumin of 4.2 gm/dL, and a urine protein/creatinine ratio of 0.87 [median 0.16 (range 0.02-6.52)]. Remission was complete in 75% of the patients and partial in 17%. One patient (8%) with chronic kidney disease (stage 2) was unresponsive to therapy. Complete remission was significantly associated with the absence of chronic histological changes (p = 0.03). In conclusion, children with NS and/or NRP associated with MGN appear to have a good prognosis when treated with a combination of corticosteroids and cyclophosphamide.

Idiopathic membranous nephropathy in pediatric patients: presentation, response to therapy, and long-term outcome

Background

Idiopathic membranous nephropathy (IMN) is one of the most common causes of primary nephrotic syndrome in adults. However, it is a relatively rare entity in the pediatric population and there is a paucity of data about the incidence, prognosis, and optimal treatment of IMN in children and adolescents. We conducted this study to evaluate pediatric patients with IMN in order to clarify the presentation, response to therapy, and clinical outcome.

Methods

A retrospective chart review was performed on patients identified with biopsy-proven IMN between 1988–2005. Patients with systemic lupus erythematosus or hepatitis-related lesions were excluded. The following data were tabulated: age, gender, ethnicity, presenting clinical and laboratory findings, proteinuria in a first morning urine specimen, estimated glomerular filtration rate (GFR_e), histopathology, type and duration of treatment, and clinical status at final evaluation.

Results

13 cases of IMN were identified out of 460 renal biopsies performed for evaluation of primary kidney disease during the study interval. Mean age was 9.6 ± 4.6, gender 6 M:7 F, ethnicity 8 W:2 B:3 H. At the initial visit hematuria was present in 9 patients, edema in 5, nephrotic-range proteinuria in 5, and hypertension in 3. Mean urinary protein:creatinine ratio 3.3 ± 2.5 and all patients had a normal GFR_e. Classic glomerular findings of IMN were seen in all renal specimens, with concomitant interstitial changes in 2 cases. Treatment included an angiotensin converting enzyme inhibitor or angiotensin receptor blocker in 11 cases. Most patients were also given immunosuppressive medications – prednisone in 10, a calcineurin inhibitor in 5, and mycophenolate mofetil or azathioprine in 3 patients. At the last follow-up, 42 ± 35 months after the diagnostic biopsy, 7 children were hypertensive and the urine protein:creatinine ratio was 2.3 ± 3.1. The mean GFR_e was 127 ± 57 mL/min/m². Three patients had Chronic Kidney Disease Stage 3, all of whom were also hypertensive.

Conclusion

IMN is a rare but serious glomerulopathy in pediatrics. We estimate that it accounts for approximately 3% of renal biopsies. Long-term prognosis is guarded because approximately 50% of patients may have evidence of progressive kidney disease.

Idiopathic membranous nephropathy in children

Idiopathic membranous nephropathy (MN) is a rare cause of asymptomatic proteinuria (AP) or nephrotic syndrome (NS) in childhood. To improve our understanding of its clinical course, we retrospectively reviewed 19 cases of idiopathic MN seen in our hospital over a period of 28.5 years, i.e., from January 1977 to July 2005. Eight patients (39%) had AP and 11 (61%) presented with NS. All eight AP patients achieved remission, regardless of treatment modality. Oral corticosteroid was given to all 11 NS patients, but only three of them responded to corticosteroid. Of the eight steroid non-responders, three achieved remissions with the addition of cyclosporine, and the five who were not administered additional immunosuppressive drugs had persistent NS. At the latest evaluation, all six NS patients that achieved remission remained free of proteinuria and had a normal renal function. Moreover, two of the 5 steroid non-responders showed persistent nephrotic-range proteinuria but a stable renal function. The remaining three steroid non-responders progressed into chronic renal insufficiency, and this progression was preceded by renal vein thrombosis (RVT) in two of the three patients. Presentation with NS (P=0.045) and the development of RVT (P=0.010) were identified as poor prognostic factors.

Validation of a predictive model of idiopathic membranous nephropathy: its clinical and research implications

Although a number of factors have consistently correlated with progression to chronic renal insufficiency (CRI) in idiopathic membranous glomerulonephropathy (IMGN), they appear late, are not quantitative in nature and have not been validated. We have determined that the highest sustained six-month period of proteinuria is an important predictor of progression. Using multiple logistic modelling, the only additional prognostic variables of importance in 184 Canadian patients were the initial creatinine clearance and the rate of change in function over this six-month interval. Independent data from Italy (101 patients) and Finland (78 patients) were obtained for comparison. Sensitivity, specificity, negative and positive predictive values and overall accuracy, as well as Pearson's goodness-of-fit and Harrell's "C" statistic were used to assess the fits of the model. Accuracy of prediction was > or = 85% in all three countries. Pearson's Chi-square goodness-of-fit showed good agreement across the spectrum and Harrell's "C" statistic was > or = 90%. Therefore, a predictive, semiquantitative algorithm in IMGN has been validated. Its relevance in patient management and in clinical trials is illustrated.