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Primary Membranous Nephropathy
What is Primary Membranous Nephropathy?
Primary membranous nephropathy (pMN) is an autoimmune disease that affects the functions of the kidney. Autoimmune diseases are illnesses in which the human body’s immune system targets otherwise healthy cells. In pMN, the immune system attacks the glomeruli: small filtering units inside the kidneys. This causes changes to the membrane (made of special cells called podocytes) in the glomerulus that filters the blood. The abnormal podocytes allow large amounts of protein to leak into the urine. Each kidney contains around one million glomeruli. Several glomerular diseases may lead to nephrotic syndrome, and pMN is one of the most common.
People with nephrotic syndrome may have high blood pressure, swelling of the face, arms, legs, feet, or other areas, as well as other health implications. Although there has been recent progress in discovering the underlying mechanisms behind pMN, much research is required to understand how the autoimmune reaction is triggered in the disease.
What are the symptoms of Primary Membranous Nephropathy?
pMN progresses relatively slowly over time, and thus, someone affected by pMN might not notice it immediately. The most common signs and symptoms of pMN include:
- Weight gain
- Tiredness (fatigue)
- High cholesterol levels
- Low protein level in the blood (hypoproteinemia)
- Swelling in the ankles, legs, and other parts of the body (edema)
- Foamy urine as a result of protein leaking into the urine (proteinuria)
Additionally, only some people with these symptoms will have pMN. Other, more common conditions may cause them too. But if you have any symptoms, it is important to get them checked by your doctor.
What Causes Primary Membranous Nephropathy? Who is at risk of Primary Membranous Nephropathy?
In pMN, podocytes that form the filtering membrane are attacked by antibodies produced by the immune system. As a result, the podocytes lose their ability to retain proteins in the blood, allowing proteins to leak into urine. Factors known to increase a person's chance of developing a disease are called ‘risk factors’. Having a risk factor does not mean that one will develop a particular condition, but the more risk factors one has, the more likely it is that one may develop that specific illness. pMN most commonly occurs above the age of 40, with the highest rate of new cases between the ages of 50 to 60. pMN is more common among males than females, and females often have better outcomes. Globally, there are 8 to 10 new cases per 1 million population yearly, and white males are at a higher risk of developing pMN than other ethnicities. People living with other diseases that may cause damage to the kidneys, such as cancer and lupus, also have an increased risk.
How is Primary Membranous Nephropathy diagnosed?
If your doctor thinks you might have pMN, they may suggest a urine test, a blood test, a glomerular filtration rate (GFR) test, or a kidney biopsy. In pMN, urine tests help find traces of protein and blood in the urine, while a blood test could identify low levels of protein and elevated cholesterol in the blood. Glomerular Filtration rate (GFR) is a calculated measure from a blood test that checks how well the kidneys function. It is needed when investigating the filtering functions of the kidneys because a low eGFR (an estimated level of GFR) can be a predictor of pMN. A kidney biopsy is an important test and is often recommended for confirming a diagnosis of pMN. Newer tests have been developed that can help in diagnosing pMN. A specific type of protein produced by the immune response (an autoantibody), called PLA2R, can be detected in around 7 out of 10 people with pMN. The availability of this test means that a kidney biopsy may not always be required to confirm a diagnosis of pMN.
What treatment options are available for Primary Membranous Nephropathy?
If you have been diagnosed with pMN, several treatments can help treat the condition and support recovery. First, symptomatic management is done through blood pressure medicines, cholesterol medicines, salt-intake restriction, and blood thinners. Blood pressure medicines are used to reduce blood pressure. Around 1 out of 3 people respond to these treatments, and about 1 in 3 people will additionally require one of the following therapies:
- Therapy that lowers the activity of the body’s immune system (immunosuppressive therapy)
- Therapy that replaces the standard blood-filtering functions of the kidneys (renal replacement therapy)
What is the outlook for a person with Primary Membranous Nephropathy?
Clinical studies investigate new treatments for people living with pMN and often include people who do not respond or who stop responding to available medicines. Generally, people with pMN with fewer signs and symptoms of the disease often have a good long-term prognosis, and in some cases, show remission in symptoms and signs without any treatment. However, some people with pMN may progress to kidney failure. Clinical trials are designed to examine how safe new medicines or procedures are and how well they work. The new medicine or procedure may be compared with already available treatments.
If you want to know more about Roche-sponsored clinical trials or are interested in participating in a clinical trial, speak to your doctor or visit the Roche ForPatients clinical trials page.
References
Couser WG. Primary membranous nephropathy. Clin J Am Soc Nephrol [Internet]. 2017 Jun; 12(6):983-997. Available from: Link doi: Link
National Institute of Diabetes and Digestive and Kidney Diseases. Glomerular Diseases [Internet]. Accessed 17 January 2023. Available from: Link
Lai WL, Yeh TH, Chen PM et al. Membranous nephropathy: A review on the pathogenesis, diagnosis, and treatment. J Formos Med Assoc [Internet]. 2015 Feb;114(2):102–111. Available from: Link
Cleveland Clinic. Membranous nephropathy: Causes, symptoms, treatment, recovery [Internet]. Accessed 17 January 2023. Available from: Link
Alok A, Yadav A. Membranous nephropathy. StatPearls [Internet]. Updated 11 June 2022. Accessed 17 January 2023. Available from: Link
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