The M-type phospholipase A2 receptor (PLA2R) in the glomerular podocyte has been identified as the major target antigen in deposited immune-complexes.
Membranous nephropathy mostly affects adults, in whom it is a common cause of nephrotic syndrome.
Etiology of Membranous Nephropathy
Membranous nephropathy is usually idiopathic, but it may be secondary to any of the following:
Infections (eg, hepatitis B or C virus infection, syphilis, HIV infection)
Autoimmune disorders (eg, systemic lupus erythematosus [SLE])
Thyroiditis
Cancer
Parasitic diseases (eg, malaria, schistosomiasis, leishmaniasis)
Depending on the patient’s age, 4 to 20% have an underlying cancer, including solid cancers of the lung, colon, stomach, breast, or kidney; Hodgkin or non-Hodgkin lymphoma; chronic lymphocytic leukemia; and melanoma.
Membranous nephropathy is rare in children and, when it occurs, is usually due to hepatitis B virus infection, SLE, or autoimmune thyroid disease.
Renal vein thrombosis is more frequent in membranous nephropathy and is usually asymptomatic but may manifest with flank pain, hematuria, and hypertension. It may progress to pulmonary embolism.
Symptoms and Signs of Membranous Nephropathy
Patients typically present with edema and nephrotic-range proteinuria and occasionally with microscopic hematuria and hypertension. Symptoms and signs of a disorder causing membranous nephropathy (eg, a cancer) may be present initially.
Diagnosis of Membranous Nephropathy
Renal biopsy
Evaluation for secondary causes
Diagnosis is suggested by development of nephrotic syndrome, particularly in patients who have potential causes of membranous nephropathy. The diagnosis is confirmed by renal biopsy.
Proteinuria is in the nephrotic range in 80% of patients. Laboratory testing is done as indicated for nephrotic syndrome. The glomerular filtration rate (GFR), if measured, is normal or decreased.
Immune complexes are seen as dense deposits on electron microscopy (see figure Electron microscopic features in immunologic glomerular disorders). Subepithelial dense deposits occur with early disease, with spikes of lamina densa between the deposits. Later, deposits appear within the glomerular basement membrane (GBM), and marked thickening occurs. A diffuse, granular pattern of IgG deposition occurs along the GBM without cellular proliferation, exudation, or necrosis.
Identifying presence or absence of PLA2R antibody and the subclass of IgG deposits may help to differentiate idiopathic from secondary membranous nephropathy. For example, the deposits in idiopathic membranous nephropathy are PLA2R antibody positive and predominantly IgG 4, whereas PLA2R antibody is typically negative and IgG 1 and 2 predominate in malignancy-associated membranous nephropathy (1).
Electron microscopic features in immunologic glomerular disorders
Medium-sized subepithelial dense deposits are seen on transmission electron microscopy in late stage I disease (×10,200).
Image provided by Agnes Fogo, MD, and the American Journal of Kidney Diseases' Atlas of Renal Pathology (see www.ajkd.org).
Spikes of basement membrane silver-staining material protrude from the basement membrane (high-power oil-immersion view, Jones silver stain, original magnification ×1000).
Image provided by Agnes Fogo, MD, and the American Journal of Kidney Diseases' Atlas of Renal Pathology (see www.ajkd.org).
Diffuse coarsely granular IgG deposition along glomerular capillary walls (immunofluorescence with anti-IgG, original magnification ×100).
Image provided by Agnes Fogo, MD, and the American Journal of Kidney Diseases' Atlas of Renal Pathology (see www.ajkd.org).
Medium-sized subepithelial dense deposits are seen on transmission electron microscopy in late stage I disease (×10,200).
Image provided by Agnes Fogo, MD, and the American Journal of Kidney Diseases' Atlas of Renal Pathology (see www.ajkd.org).
Spikes of basement membrane silver-staining material protrude from the basement membrane (high-power oil-immersion view, Jones silver stain, original magnification ×1000).
Image provided by Agnes Fogo, MD, and the American Journal of Kidney Diseases' Atlas of Renal Pathology (see www.ajkd.org).
Diffuse coarsely granular IgG deposition along glomerular capillary walls (immunofluorescence with anti-IgG, original magnification ×100).
Image provided by Agnes Fogo, MD, and the American Journal of Kidney Diseases' Atlas of Renal Pathology (see www.ajkd.org).
Diagnosis of cause
Evaluation of patients diagnosed with membranous nephropathy usually includes the following:
A search for occult cancer, particularly in a patient who has lost weight, has unexplained anemia or heme-positive stools, or is older
Consideration of drug-induced membranous nephropathy
Antinuclear antibody testing
The search for occult cancer is usually limited to age-appropriate screening.
Diagnosis reference
1. Beck LH , Bonegio RG, Lambeau G: M-type phospholipase A2 receptor as target antigen in idiopathic membranous nephropathy. N Engl J Med 361(1):11, 2009. doi: 10.1056/NEJMoa0810457
Treatment of Membranous Nephropathy
Control of nephrotic-range proteinuria and/or edema with diuretics
Treatment of secondary causes of nephrotic syndrome as indicated
Immunosuppressive therapy for patients with symptomatic idiopathic membranous nephropathy at high risk of progression
Kidney transplantation for patients with end-stage kidney disease
Primary treatment is that of the causes. Among patients with idiopathic membranous nephropathy, asymptomatic patients with non–nephrotic-range proteinuria do not require treatment; renal function should be monitored periodically (eg, twice yearly when apparently stable).
Patients with nephrotic-range proteinuria who are asymptomatic or who have edema should be treated with diuretics.
Immunosuppressive therapy
Immunosuppressants should be considered only for patients with symptomatic idiopathic membranous nephropathy and for those most at risk of progressive disease. While there is no strong evidence that immunosuppressive therapy has a long-term benefit for patient or kidney survival, it appears to improve rates of remission and possibly progression to end-stage kidney disease (ESKD) (1, 2, 3). Older and chronically ill patients are at greater risk of infectious complications due to immunosuppressants.
Therapies of unproven long-term value include IV immune globulin and nonsteroidal anti-inflammatory drugs (NSAIDs).
Kidney transplantation is an option for patients with end-stage kidney disease. Membranous nephropathy recurs in about 10% of patients, with loss of graft in up to 50%.
Treatment references
1. von Groote TC, Williams G, Au EH, et al: Immunosuppressive treatment for primary membranous nephropathy in adults with nephrotic syndrome. Cochrane Database Syst Rev 11(11):CD004293, 2021. doi: 10.1002/14651858.CD004293.pub4
2. Fervenza FC, Appel GB, Barbour SJ, et alN Engl J Med 381(1):36-46, 2019. doi: 10.1056/NEJMoa1814427
3. Ponticelli C, Altieri P, Scolari F, et alJ Am Soc Nephrol 9(3):444, 1998. doi: 10.1681/ASN.V93444
Prognosis for Membranous Nephropathy
About 25% of patients undergo spontaneous remission, 25% develop persistent, non–nephrotic-range proteinuria, 25% develop persistent nephrotic syndrome, and 25% progress to end-stage kidney disease. Women, children, and young adults with non–nephrotic-range proteinuria and patients with persistently normal renal function 3 years after diagnosis tend to have little disease progression. More than 50% of patients with nephrotic-range proteinuria who are asymptomatic or who have edema that can be controlled with diuretics will have a partial or complete remission within 3 to 4 years.
Risk of progression to renal failure is highest among patients with
Persistent proteinuria ≥ 8 g/day, particularly men age > 50 years
An elevated serum creatinine level at presentation or diagnosis
Biopsy evidence of substantial interstitial inflammation
Key Points
Membranous nephropathy is usually idiopathic; however, patients may have treatable associated disorders, such as cancers, autoimmune disorders, or infections.
Initial manifestations are typically those of nephrotic syndrome (eg, edema, nephrotic-range proteinuria, occasionally microscopic hematuria and hypertension).
Confirm the diagnosis with renal biopsy and consider associated disorders and causes.
Treat symptoms of nephrotic syndrome and treat hypertension initially with angiotensin inhibition.
Consider immunosuppressive therapy only for patients with idiopathic membranous nephropathy who are at risk for progression.
