Does this patient have membranous nephropathy?

Membranous nephropathy (MN) is one of the most common causes of nephrotic syndrome in adults and is found in 15 to 33% of kidney biopsies performed for heavy proteinuria. MN derives its name from its histological pattern on light microscopy: glomerular basement membrane (GBM) thickening with minimal or absence of cellular proliferation.

Primary (idiopathic) MN is the most common form and accounts for over two thirds of biopsy proven cases of MN. It is seen in men and women of all races and ethnicities. Men are affected more commonly than women (ratio 2:1 to 3:1). It may occur in all age groups but there are two peaks of incidence between 30-40 years and 50-60 years.

MN can also be secondary to various infections, drugs, toxins, autoimmune diseases and cancers. Although numerous associations have been reported, those most frequently encountered and likely to be causative of secondary MN are hepatitis B infection, class V lupus nephritis, medications and toxins (nonsteroidal anti-inflammatory drugs, gold salts, penicillamine, and mercury salts) and solid tumors of the colon, lung and breast. Parasitic infections (malaria and schistosomiasis) are potential causes of secondary MN in patients from the developing world, and secondary syphilis may also be causative.

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MN is relatively uncommon in children; when present it is more often secondary to hepatitis B, autoimmune or thyroid diseases, although primary disease can occur as well. In young women, the diagnosis of MN should raise the suspicion of lupus nephritis. Recently, children with early-onset MN were found to have circulating antibodies reactive with the cationic bovine serum albumin (BSA), which were found both in the blood and within immune deposits in the kidney. It is hypothesized that absorption of intact, modified BSA present in formula from the infant’s underdeveloped digestive tract results in the generation of anti-BSA antibodies and binds to anionic residues in the GBM where it serves as a planted antigen for the formation of immune deposits in situ.

Recently, children with early-onset MN were found to have circulating antibodies reactive with the cationic bovine serum albumin (BSA), which were found both in the blood and within immune deposits in the kidney. It is hypothesized that absorption of intact, modified BSA present in formula from the infant’s underdeveloped digestive tract results in the generation of anti-BSA antibodies and binds to anionic residues in the GBM where it serves as a planted antigen for the formation of immune deposits in situ.

It is hypothesized that absorption of intact, modified BSA present in formula from the infant’s underdeveloped digestive tract results in the generation of anti-BSA antibodies and binds to anionic residues in the GBM where it serves as a planted antigen for the formation of immune deposits in situ.

The differential diagnosis of MN includes all the causes of the nephrotic syndrome such as: minimal change disease, focal segmental glomerulosclerosis (FSGS), diabetic nephropathy, amyloidosis and membranoproliferative glomerulonephritis. Kidney biopsy is required to make the diagnosis of MN and helps to distinguish primary MN from secondary forms of MN and other causes of nephrotic syndrome.

Summary – key presenting findings

Edema and proteinuria are the major signs of MN and 70 to 80% of the patients present with nephrotic syndrome. Up to 50% have microscopic hematuria but red blood cell casts and macroscopic hematuria are not typically present. Glucosuria without hyperglycemia may be present and suggests proximal tubule dysfunction from heavy proteinuria. Blood pressure and renal function are normal in almost 70% of patients at presentation.

Loss of kidney function in MN is usually gradual and acute kidney injury is uncommon. When it occurs, acute kidney injury is often most often due to aggressive diuresis, drug-induced acute interstitial nephritis, or superimposed crescentic glomerulonephritis.

Bilateral flank pain in a patient with heavy proteinuria (>8 grams/day) and acute renal failure should raise the suspicion of renal vein thrombosis.

Clinical presentation and history

Most patients with MN present with non-specific symptoms of weight gain and/or edema over several weeks. They may have noticed foaminess of the urine. Occasionally, patients present with acute onset of dyspnea and/or pleuritic chest pain from pulmonary embolism.

To exclude potential secondary causes of MN, a careful history is required to determine if there has been exposure to potentially offending medications, toxins (eg, mercury-containing skin-lightening creams), travel to or origin from areas endemic for infectious causes of MN, risk factors for hepatitis, or symptoms suggestive of systemic lupus erythematosus or autoimmune thyroid disease.

Patients should be questioned about age-appropriate cancer screening and risk factors for cancer (especially cigarette smoking). Although familial MN is rare, a family history of kidney and autoimmune diseases should be obtained.

Physical findings

Weight gain and edema are generally the only findings on physical examination. Anasarca, with ascites, scrotal swelling and pleural effusions may be present, but pulmonary congestion and elevated jugular pressure are not features of nephrotic syndrome. Blood pressure is usually normal at first presentation but may be elevated later in the course of the disease.

An office urinalysis should be performed, as the presence of a strongly positive dipstick test for albumin will quickly establish the diagnosis of nephrotic syndrome.

The rest of the examination should be directed at determining if there are any signs of a secondary cause of MN.

What tests to perform?

Nephrotic syndrome is defined by the presence of heavy proteinuria (greater than 3 gram/24 hours), Hypoalbuminemia (less than 3 grams/dl), and peripheral edema. Hyperlipidemia, hypercoagulability and hypogammaglobulinemia with increased risk for infection may also be present.

  • Standard blood and urine tests establish the diagnosis of of nephrotic syndrome and its associated abnormalities as well as the level of renal function.

  • The definitive diagnosis of MN relies on kidney biopsy.

  • Other tests establish whether MN is primary or secondary to another disease.

Standard laboratory tests for nephrotic syndrome

  • In addition to serum creatinine, electrolytes and complete blood count (CBC), all patients presenting with nephrotic syndrome should have serum albumin and a fasting lipid panel measured.

  • Since patients with nephrotic syndrome may become vitamin D deficient due to loss of vitamin D-binding protein in the urine, 25-OH vitamin D levels should be measured.

  • Urinalysis typically shows lipiduria (oval fat bodies, lipid droplets and fatty casts) in addition to albuminuria. Mild microscopic hematuria may be present in MN (both primary and secondary).

  • A 24 hour urine collection should be obtained to quantify the amount of proteinuria. By measuring creatinine excretion on this 24 hour urine specimen, one can calculate creatinine clearance and also establish a baseline ratio of urine protein to creatinine. This will allow comparisons of the urine protein to creatinine ratios in subsequent “spot” urine samples, a more convenient method for monitoring of disease progression and response to therapy.

Renal biopsy – Light microscopy

  • Diffuse thickening of the GBM affecting all glomeruli without hypercellularity (Figure 1).

  • In many cases and with the use of silver stains, “spikes” reflecting extensions of GBM between the sub-epithelial immune deposits can be seen (Figure 2).

  • The presence of glomerular hypercellularity is suggestive of a secondary form of membranous nephropathy.

Figure 1.

Idiopathic MN. Glomerular basement membranes are diffusely thickened. Some capillary loops exhibit a rounded, “stiff” appearance. There is no increase in cellularity. PAS, 40× (0.1875 micron/pixel). Image provided by Dr. Joel Henderson, Pathology Department, Boston University.

Figure 2.

Glomerular basement membranes are diffusely thickened, and show numerous characteristic spike-like projections on the outer aspect. Jones silver methenamine, 120× (0.0625 micron/pixel). Image provided by Dr. Joel Henderson, Pathology Department, Boston University.

Renal biopsy – Immunofluorescence

  • Diffuse granular pattern of IgG (Figure 3) and C3 along the GBM (Figure 4)

  • IgG4 predominates in primary MN; whereas the predominance of other IgG subclasses is characteristic of secondary forms of MN.

  • In patients with negative anti-PLA2R antibodies in the serum or in whom a serum test is not available, staining of the kidney tissue biopsy for the PLA2R antigen within immune deposits can be helpful in identifying cases with PLA2R-associated MN. Positive tissue staining for PLA2R and a negative serological test for anti-PLA2R indicates that the patient has PLA2R-associated MN and may have entered a serological remission. Positive tissue staining for PLA2R also helps differentiate recurrent primary MN from de novo MN after transplantation.

Figure 3.

Diffuse granular pattern of IgG along the GBM.

Figure 4.

Diffuse granular staining of C3 along the GBM.

Renal biopsy – Electron microscopy

  • The pathognomonic lesions on electron microscopy are the presence of sub-epithelial dense deposits with effacement of the overlying podocyte foot processes (Figure 5).

  • Podocyte injury triggers the deposition of new extracellular matrix between and around the immune deposits, which contributes to the GBM thickening (Figure 5).

  • In primary MN, deposits are limited to the sub-epithelial space whereas the presence of mesangial or sub-endothelial deposits is suggestive of a secondary cause of MN.

  • The presence of tubuloreticular structures in the glomerular endothelial cells is very suggestive of lupus MN.

Figure 5.

Left panel: Glomerular capillary walls are distorted by numerous subepithelial electron densities (asterisks). The overlying podocyte foot processes are effaced, and podocytes reveal other features of injury including cell swelling and formation of microvilli. The endothelium is normal. There are no subendothelial or mesangial electron densities. Transmission electron micrograph, 6000×. Right panel: The subepithelial electron densities (asterisks) exhibit a granular texture. Many densities are flanked by spike-like projections of basement membrane material (white arrows); some are completely enclosed by a thin layer of new basement membrane material (black arrows). Transmission electron micrograph, 15000×. CL – capillary lumen; US – urinary space; P – podocyte; M – mesangium. Images provided by Dr. Joel Henderson, Pathology Department, Boston University.

Serological and other tests

  • Once the diagnosis is established by renal biopsy, serologic tests help to distinguish between primary and secondary forms of MN.

  • Serum complement levels are typically normal in primary MN.

  • A positive antinuclear antibody (ANA) suggests the possibility of MN secondary to lupus, especially if associated with low complement levels (eg, low C3). However, a negative ANA and normal C3 do not exclude the diagnosis of lupus nephritis, particularly in a young female with biopsy-proven MN.

  • The erythrocyte sedimentation rate is typically elevated in patients with nephrotic syndrome and does not help to distinguish primary from secondary MN.

  • Serologic tests for hepatitis should be obtained, as hepatitis B, and occasionally hepatitis C, may be causally associated with MN.

  • The recent discovery of circulating autoantibodies against the M-type phospholipase A2 receptor (PLA2R- a transmembrane glycoprotein expressed on podocytes) in patients with primary MN, will have applications in the diagnosis and monitoring of treatment response in such patients. This test is highly specific for primary MN and a positive test is diagnostic in cases that cannot undergo kidney biopsy. Approximately 70-80% of patients with clinically active primary MN will test positive for anti-PLA2R antibodies when measured with either ELISA or immunofluorescence testing (both commercially available in Europe and the US). Patients with high titers of anti-PLA2R antibodies are less likely to develop spontaneous remission or achieve complete remission when treated with immunosuppressive therapy, suggesting a more aggressive disease. In patients with MN who respond to treatment, a decrease in anti-PLA2R titer (immunological response) typically precedes the decrease in proteinuria (clinical response). Lower levels of anti-PLA2R can be detected in 50% of patients with partial remission (PR), suggesting that not all patients with PR have reached full immunological recovery. These data support potential roles of anti-PLA2R antibody in the diagnosis of primary MN and in predicting response to therapy and prognosis. Serial measurements of anti-PLA2R antibodies could be used to monitor response to immunosuppressive therapy. The test is only offered clinically at select centers in the US, but is anticipated to be more widely available in the near future. Another 5 to 9% of patients with primary MN and negative anti-PLA2R may test positive for another antibody, anti-thrombospondin type 1 domain containing 7A (anti-THSD7A) targeting another antigen (THSD7A) expressed on the podocytes. No commercial test for this antibody is available in the US so far, but testing can be performed in some specialized laboratories in the US and Europe.

  • Testing stool for occult blood loss and measurement of prostate specific antigen in males above the age of 50 years serves as a screen for cancer as a secondary cause.

Imaging studies

  • Age appropriate malignancy screening is indicated in patients with MN (mammogram in women over 40 years of age, colonoscopy in patients over 50 years of age, chest X-ray or chest CT in patients at high risk for lung cancer).

  • Patients with MN and heavy proteinuria (>8 grams/day) presenting with acute kidney injury and flank pain, should have a renal venous duplex or a magnetic resonance renal venogram to rule out the possibility of renal vein thrombosis.

  • Patients presenting with sudden onset of dyspnea and/or pleuritic chest pain should be investigated promptly for the possibility of pulmonary embolism.

How should patients with membranous nephropathy be managed?

  • Initiate conservative management of nephrotic syndrome.

  • Identify potentially reversible secondary causes.

  • Establish prognostic category (low or high risk of progression).

  • Select an immunosuppressive regimen for those that fail to show signs of spontaneous remission within 6 months, have intractable edema, or have poor prognostic features.

Conservative management of nephrotic syndrome

  • All patients with MN and proteinuria should receive an angiotensin converting enzyme inhibitor (ACEi) or angiotensin 2 type 1 receptor blocker (ARB). By lowering intraglomerular pressure, these agents help to lower proteinuria and reduce the risk of disease progression. Goal of blood pressure should be less than 130/80 mmHg.

  • Dietary salt restriction and diuretics are often required for the treatment of the edema related to nephrotic syndrome.

  • Statins should be used for the treatment of severe hypercholesterolemia associated with nephrotic syndrome.

  • Vitamin D supplementation with ergocalciferol is recommended although total 25-OH vitamin D levels may remain low even with supplementation because of urinary loss of vitamin D binding protein.

  • The use of anticoagulation in patients with severe proteinuria remains controversial. Some experts recommend the use of anticoagulation in patients with severe proteinuria (more than 8-9 grams/day) and severe hypoalbuminemia (less than 2.8 grams/dl). Others initiate anticoagulation only after a thrombotic event.

Treat or eliminate reversible secondary causes

  • Before any therapeutic intervention, it is very important to differentiate between primary or secondary forms of MN (see above biopsy and testing sections).

  • Remission of proteinuria may follow successful treatment of infections. In particular, anti-viral therapy of hepatitis B may lead to remission of MN.

  • Please refer to the section on lupus nephritis for the treatment of lupus MN.

  • Elimination of potential offending drugs (eg., NSAIDs, gold salts, penicillamine) or toxins (mercury skin lightening creams) may result in complete or partial remission, although the clinical improvement may take place over the course of months.

Prognostication in membranous nephropathy

  • Risk factors for progressive disease include: older age (>50 years old), severe proteinuria (>8 grams/day) for more than 6 months, male sex, elevated creatinine at time of presentation, and advanced tubulo-interstitial fibrosis on kidney biopsy.

Immunosuppressive therapy of primary membranous nephropathy

  • Corticosteroid therapy alone is generally ineffective in primary MN.

  • Immunosuppressive treatments for MN should be used in consultation with a nephrologist familiar with such agents and their side effects.

  • We recommend as first-line therapy, a 6-month course of cyclophosphamide with glucocorticoids. This can be given as a daily regimen of cyclophosphamide (1.5-2 mg/kg/day) with a 3-month tapering course of prednisone (starting at 60 mg/day) or as a 6-month course of alternating prednisone and cyclophosphamide as described by Jha et al. Complete or partial remission of nephrotic syndrome has been reported in about 70% of MN patients treated for 6 months with alternating prednisone and cyclophosphamide. They also had a reduced risk of doubling serum creatinine and progression to end stage renal disease, and had a better quality of life when followed for 10 years. Men contemplating fathering children in the future should be advised to bank sperm because of the risk of infertility. Vaccination against Herpes zoster and Bactrim prophyalxis is advisable and regular checks of leukocyte count should be performed to avoid excessive bone marrow suppression.

  • Treatment with calcineurin inhibitors (cyclosporine or tacrolimus) with low dose prednisone is an effective alternative in patients in whom cyclophosphamide is contraindicated. This regimen is associated with a high risk of relapse when the calcineurin inhibitors are stopped so longer duration of therapy is often required. Calcineurin inhibitors are nephrotoxic, therefore the drug dose is adjusted to achieve trough levels that are lower than those used to prevent transplant rejection.

  • Rituximab, an anti-CD20 monoclonal antibody, has also been shown to induce partial or complete remission of proteinuria in a limited number of uncontrolled studies involving patients with non-advanced histological lesions on kidney biopsy. It is relatively safe and well tolerated. Long term follow-up data is not yet available.

  • Mycophenolate mofetil (MMF) in combination with steroids, has been used successfully in uncontrolled trials in a limited number of patients with primary MN, however one can not exclude the possibility of reporting bias and its role needs confirmation in randomized controlled trials. MMF is an effective treatment for the MN associated with lupus.

  • Synthetic adrenocorticotropic hormone (ACTH) induced a high rate of complete and sustained remission of proteinuria in small studies of patients with primary MN. Larger studies are required to further determine the efficacy and safety of this drug.

  • Clinical response is monitored by measuring urine protein excretion to assess for partial (<3 g/day) or complete (<0.3 g/day) remission. If no apparent response is achieved after 6 months, an alternative agent should be considered.

What happens to patients with membranous nephropathy?

Idiopathic MN may be associated with complete spontaneous remission in 15% to 30% of patients followed for 5 years. The remaining patients will either remain with a variable degree of proteinuria or progress to end-stage renal disease. Patients with MN and nephrotic range proteinuria have an increased risk of death from cardiovascular disease and thrombotic events. Several factors contribute to cardiovascular events, including hyperlipidemia, hypertension, and hypercoagulability.

Patients with ESRD from primary MN are suitable candidates for kidney transplantation, however the disease may recur after successful transplantation. The rate of recurrence varies from 5 to 40% (the latter represent recurrences diagnosed on protocol biopsies). Recurrent MN is often progressive and may lead to graft failure, however treatment with Rituximab has been effective in inducing partial or complete remission. Testing for anti-PLA2R at time of kidney transplantation might be helpful to predict the risk of disease recurrence in the allograft. The presence of anti-PLA2R antibodies at time of kidney transplant has a positive predictive value of disease recurrence of more than 80%. Serial monitoring of anti-PLA2R levels after kidney transplantation or after treatment of MN recurrence, might predict the clinical outcome. Disappearance of circulating anti-PLA2R usually precedes clinical remission; persistence or re-appearance of anti-PLA2R after kidney transplantation is suggestive of worse clinical outcome (e.g proteinuria and graft dysfunction).

In those cases that progress to ESRD, deterioration of renal function typically occurs over the course of several years as a result of glomerular sclerosis and interstitial fibrosis. In any patient in whom the course suddenly accelerates, a repeat renal biopsy should be considered (after excluding over-diuresis or renal vein thrombosis as possible causes) because superimposed crescentic glomerulonephritis from anti-GBM or ANCA-associated disease has been reported.

Primary membranous nephropathy is an organ-specific autoimmune disease in which circulating autoantibodies target an antigen expressed on the podocyte foot processes. The major human podocyte antigen is the M-type phospholipase A2 receptor (PLA2R), and anti-PLA2R autoantibodies are detectable in 70-80% of patients with primary MN. Genome-wide association studies of Caucasian patients with primary MN have identified risk alleles in the genes encoding HLADQA1 and PLA2R. This indicates that there is a genetic susceptibility at the level of the immune response as well as at the target organ, although familial cases of MN are very uncommon.

Alloantibodies to neutral endopeptidase (NEP), also expressed on human podocytes, have been described in rare cases of antenatal membranous nephropathy in babies born to NEP-deficient mothers. Studies in experimental MN have shown that podocyte injury and proteinuria are due to complement activation and assembly of the membrane attack complex (C5b-C9).

How to utilize team care?

  • Nephrology consultation – The diagnosis and management of patients with MN requires special expertise, therefore we strongly recommend that all patients with nephrotic syndrome be managed in close consultation with a nephrologist so as not to delay the diagnosis and institution of appropriate therapy.

  • Dietitians play an important role in the management of patients with nephrotic syndrome. Patients with MN and nephrotic syndrome are at high risk of protein malnutrition, vitamin D deficiency and sodium-dependent edema. A balanced diet that provides all the essential amino acids is very important for the well being of such patients. Salt restriction is essential for the management of edema associated with nephrotic syndrome. Vitamin D supplementation is required due to the ongoing losses of vitamin D binding protein in the urine of patients with nephrotic syndrome.

  • Pharmacists – Drug clearance may be affected by impaired renal function, and hypoalbuminuria alters the availability of protein-bound drugs. Therefore, consultation with a pharmacist about drug dosing, drug interactions and specific toxicities in this population is advisable, particularly with regard to the immunosuppressive agents used for the treatment of MN.

Are there clinical practice guidelines to inform decision making?

  • Most of the patients with MN have nephrotic syndrome. Clinical practice guidelines apply to all patients with heavy proteinuria. Administration of ACEi or ARB is essential for reducing proteinuria and forestalling the progression to end stage renal disease. Salt restriction and the use of loop diuretics help to improve the edema. High doses of loop diuretics are often required for better response to treatment. Hyperlipidemia occurs commonly with nephrotic syndrome and usually improves with the resolution of the disease. Statins are commonly used for the treatment of severe hyperlipidemia associated with nephrotic syndrome. Anticoagulation should be used in all nephrotic patients with venous thrombotic events and continued as long as the nephrotic syndrome is present.

Other considerations

ICD-10 codes

  • N04.2 Nephrotic syndrome with diffuse membranous glomerulonephritis

  • N05.2 Unspecified nephritic syndrome with diffuse membranous glomerulonephritis

  • N00.2 Acute nephritic syndrome with diffuse membranous glomerulonephritis

  • N03.2 Chronic nephritic syndrome with diffuse membranous glomerulonephritis

DRG codes

  • 316. Renal failure

  • 325/326/327. Kidney and urinary tract signs and symptoms

What is the evidence?

Ponticelli, C. “Membranous nephropathy”. . vol. 20. 2007. pp. 268-287. (A comprehensive review article of MN, addressing several aspects of the disease prior to the discovery of the MN antigen.)

Fervenza, FC, Sethi, S, Specks, U. “Idiopathic membranous nephropathy: diagnosis and treatment”. . vol. 3. 2008. pp. 905-919. (A detailed review of the diagnosis and various treatment options for MN.)

Beck, LH, Salant, DJ. “Membranous nephropathy: from models to man”. J Clin Invest. vol. 124. 2014. pp. 2307-2314. (A comprehensive review that details recent advances in the field of MN with a focus on pathophysiology and future direction in MN research.)

Beck, LH, Bonegio, RG, Lambeau, G, Beck, DM, Powell, DW, Cummins, TD, Klein, JB, Salant, DJ. “M-type phospholipase A2 receptor as target antigen in idiopathic membranous nephropathy”. . vol. 361. 2009. pp. 11-21. (This paper documents the discovery of PLA2R as the major antigen in primary MN and the observation that a high proportion of such patients have circulating anti-PLA2R antibodies.)

Tomas, NM, Beck, LH, Meyer-Schwesinger, C, Seitz-Polski, B, Ma, H, Zahner, G, Dolla, G, Hoxha, E, Helmchen, U, Dabert-Gay, AS, Debayle, D, Merchant, M, Klein, J, Salant, DJ, Stahl, RA, Lambeau, G. “Thrombospondin type-1 domain-containing 7A in idiopathic membranous nephropathy”. N Engl J Med. vol. 371. 2014. pp. 2277-2287. (This paper describes the discovery of a new putative antigen THSD7A responsible for 5 to 9% of cases of primary MN. Patients with primary MN who test negative for anti-PLA2R may have circulating anti-THSD7A as a cause of MN.)

Debiec, H, Guigonis, V, Mougenot, B, Decobert, F, Haymann, JP, Bensman, A, Deschênes, G, Ronco, PM. “Antenatal membranous glomerulonephritis due to anti-neutral endopeptidase antibodies”. . vol. 346. 2002. pp. 2053-2060. (This is the first report about a podocyte antigen, neutral endopeptidase, that is involved in the pathogenesis of human MN.)

Stanescu, HC, Arcos-Burgos, M, Medlar, A, Bockenhauer, D, Kottgen, A, Dragomirescu, L, Voinescu, C, Patel, N, Pearce, K, Hubank, M, Stephens, HA, Laundy, V, Padmanabhan, S, Zawadzka, A, Hofstra, JM, Coenen, MJ, den Heijer, M, Kiemeney, LA, Bacq-Daian, D, Stengel, B, Powis, SH, Brenchley, P, Feehally, J, Rees, AJ, Debiec, H, Wetzels, JF, Ronco, P, Mathieson, PW, Kleta, R. “Risk HLA-DQA1 and PLA(2)R1 alleles in idiopathic membranous nephropathy”. . vol. 364. 2011. pp. 616-626. (A genome-wide association study of Caucasian patients with primary MN from Europe and the United Kingdom identified polymorphisms in PLA2R1, the gene that encodes the phospholipase A2 receptor, and HLA-DQA1, a class II MHC receptor, as being the only two loci associated with a risk of developing primary (idiopathic) MN.)

Ponticelli, C, Zucchelli, P, Passerini, P, Cesana, B, Locatelli, F, Pasquali, S, Sasdelli, M, Redaelli, B, Grassi, C, Pozzi, C. “A 10-year follow-up of arandomized study with methylprednisolone and chlorambucil in membranousnephropathy”. . vol. 48. 1995. pp. 1600-1604. (This is a long-term follow-up of the original study that demonstrated the efficacy of an alternating 6-month course of a cytotoxic agent and corticosteroid for the treatment of primary MN.)

Jha, V, Ganguli, A, Saha, TK, Kohli, HS, Sud, K, Gupta, KL, Joshi, K, Sakhuja, V. “A randomized, controlled trial of steroids and cyclophosphamide in adults with nephrotic syndrome caused by idopathic membranous nephropathy”. . vol. 18. 2007. pp. 1899-1904. (This important paper confirms the effectiveness of a 6-month course of cytotoxic agents and prednisone in the treatment of idiopathic MN with a long period of follow up (10 years). It represents a modification of the original 'Ponticelli regimen' using oral cyclophosphamide instead of chlorambucil.)

El-Zoghby, ZM, Grande, JP, Fraile, MG, Norby, SM, Fervenza, FC, Cosio, FG. “Recurrent idiopathic membranous nephropathy: early diagnosis by protocol biopsies and treatment with anti-CD20 monoclonal antibodies”. . vol. 9. 2009. pp. 2800-2807. (A prospective protocol transplant kidney biopsy study of patients with ESRD from primary MN showing pathological evidence of recurrence in 40% of transplanted kidneys and the response to treatment with rituximab.)

Debiec, H, Lefeu, F, Kemper, MJ, Niaudet, P, Deschenes, G, Remuzzi, G, Ulinski, T, Ronco, P. “Early-Childhood Membranous Nephropathy Due to Cationic Bovine Serum Albumin”. N Engl J Med. vol. 364. 2011. pp. 2101-2110. (This study identified children with MN who were found to have circulating cationic bovine serum albumin and anti-bovine serum albumin antibodies. No circulating immune complexes were present. The immune deposits on kidney biopsy were also positive for cationic bovine serum albumin. This suggests a possible role of milk and/or formula in the development of early childhood MN.)

Hoxha, E, Thiele, I, Zahner, G, Panzer, U, Harendza, S, Stahl, RA. “Phospholipase A2 Receptor Autoantibodies and Clinical Outcome in Patients with Primary Membranous Nephropathy”. J Am Soc Nephrol. vol. 25. 2014. pp. 1357-1366. (This prospective study reports on the relation between anti-PLA2R levels and clinical outcome -spontaneous remission, complete and partial remission after immunosuppressive therapy.)

Larsen, C. P., Messias, N. C., Silva, F. G., Messias, E., Walker, P. D.. “"Determination of Primary Versus Secondary Membranous Glomerulopathy Utilizing Phospholipase A2 Receptor Staining in Renal Biopsies."”. Modern pathology. vol. 26. 2013. pp. 709-715. (This study demonstrated that positive staining for PLA2R in the glomerular immune deposits distinguishes primary from secondary MN.)

Larsen, C. P., Walker, P. D.. “"Phospholipase A2 Receptor (Pla2r) Staining Is Useful in the Determination of De Novo Versus Recurrent Membranous Glomerulopathy”. Transplantation. vol. 95. 2013. pp. 1259-1262. (This study demonstrated that positive staining for PLA2R in the glomerular immune deposits distinguishes recurrent primary MN from de novo MN after transplantation.)