Membranous Nephropathy (MN)
Membranous Nephropathy (MEM-bruh-nus nuh-FROP-uh-thee), or MN, is a rare kidney disease characterized by thickening of the filtering barrier in the kidney called the glomerular basement membrane.
Membranous Nephropathy (MN) is a rare kidney disease characterized by thickening in the part of the kidney that filters blood: the glomerular basement membrane. The thicker membrane does not work normally and causes protein that belongs in the blood to be spilled into the urine.
MN is caused by the build-up of immune complexes within the kidney that form when a person’s antibodies attack something foreign in the body. An antibody + an antigen = an immune complex.
These immune complexes are normally eliminated while still in the circulatory system, but in MN, they accumulate in the glomerular basement membrane. The inflamed membrane does not work normally and allows large amounts of protein through the barrier and into the urine (proteinuria), causing signs and symptoms known as Nephrotic Syndrome. MN is one of the most common causes of Nephrotic Syndrome.
Some symptoms of MN include:
- Swelling in parts of the body, most noticeable around the eyes, hands, feet, and abdomen (edema)
- Weight gain due to extra fluid building up in the body
- High blood pressure (hypertension)
- High fat levels in the blood (high cholesterol)
- Foamy or bubbly urine, caused by protein spilling into urine (proteinuria)
- Low levels of protein in the blood (hypoalbuminemia)
- High levels of creatinine in the blood due to your kidneys not filtering properly. Find out more about your lab values here.
The only way to differentiate Membranous Nephropathy from other primary Nephrotic Syndrome conditions is to have a kidney biopsy, a procedure in which doctors examine a tiny portion of the kidney tissue.
Other diagnostic tools may include:
- Testing for circulating anti-PLA2R antibodies in the blood
- Urinalysis: determines the amount of protein in the urine
- Blood work: determines levels of creatinine, albumin, cholesterol, and many other factors examined to rule out other causes
- Glomerular filtration rate (GFR): Your GFR estimates your kidney function by calculating blood creatinine levels with urine protein levels. Click here for a GFR calculator.
- Ultrasound: sometimes performed to get a closer look at the kidneys
MN occurs more frequently in adults than in children and is most prevalent in adults 40 years or older. It affects men at a higher rate than women, and is the most common cause of primary Nephrotic Syndrome in Caucasian adults.
MN in children is rare — it accounts for less than 5% of new pediatric diagnoses of Nephrotic Syndrome each year.
Membranous Nephropathy is known as an autoimmune disease caused by the anti-PLA2R antibodies. The recent discovery and ability to test for these antibodies have given patients and doctors a more precise diagnosis. In fact, doctors do not use the terms “primary” or “idiopathic” MN any longer! Instead, MN patients are diagnosed as anti-PLA2R positive or anti-PLA2R negative. Many patients can avoid an invasive kidney biopsy with a more simple blood test for the anti-PLA2R antibodies. (2)
In some cases, the same type of kidney injury occurs but is caused by another illness and is considered secondary Membranous Nephropathy. MN can be a secondary disease to lupus, hepatitis B and C, and even some cancers. It has also been associated with some drugs, including non-steroidal anti-inflammatory drugs. (1)
There are currently no FDA-approved medicines to treat MN. The standard first-line (initially prescribed) treatment for MN is prednisone, a corticosteroid aimed at decreasing proteinuria.
The short-term goal of treatment is to stop protein spillage completely (known as remission) or lower the amount of protein lost in the urine as much as possible. The less protein lost in the urine, the better the patient will do.
The long-term goals of treatment include preventing relapses of protein in the urine and preventing the deterioration of kidney function.
Supportive care with the use of diuretics to decrease edema and ACE inhibitors to decrease proteinuria are recommended. Immunosuppressive treatment options including steroids should also be considered, but don’t necessarily have consistent results from patient to patient.
Recent studies suggest that B cells could play a key role in the pathogenesis of MN. Drugs that cause a depletion of B cells, such as rituximab, may be beneficial in treating the root cause and therefore preventing progression of the disease.
Your nephrologist may also recommend:
- Medications that suppress your immune system
- Diuretics and a low-salt diet to help control edema
- A medication that blocks a hormone system called the renin angiotensin system (ACE inhibitor or ARB) to control blood pressure or lower urine protein
- Anticoagulants to prevent blood clots
- Statins to lower the cholesterol level
- Maintaining a healthy diet and regulating protein and fluid intake according to your nephrologist's recommendations. A healthy diet consists of low-sodium foods with an emphasis on fruits and vegetables that are low in saturated fat and cholesterol.
- Not smoking
- Taking vitamins
1. Following a low-sodium diet may help your kidneys’ function and improve your MN symptoms.
2. Finding a nephrologist that specializes in MN that you trust is very important to your long-term health.
3. Learn about your disease, treatment options, and clinical trials in order to better advocate for yourself.
4. NephCure Kidney International can help you connect with other patients and find support to manage your disease.
Over time, MN patients may go into remission, remain stable, or experience gradual loss of kidney function. While 1/3 of MN patients will go into a spontaneous remission without treatment, some patients do not respond to steroid treatments, meaning they're steroid-resistant.
Up to 40% of MN patients eventually develop end-stage kidney disease (ESKD).
There are currently no FDA-approved medicine treatments for Membranous Nephropathy — but right now, the future looks more promising than ever before. There are at least 20 potential new medicines for Nephrotic Syndrome diseases in various phases of clinical trials. These clinical trials are absolutely essential in making new treatments possible, and they need patient involvement to succeed.
That's why NephCure launched KidneyHealthGateway.com, an online platform that connects Nephrotic Syndrome patients with clinical trials in order to advance research and eventually find a cure for FSGS and other protein-spilling kidney diseases. Access breakthrough clinical trials, expert care, and one-on-one patient support all in one place — click here to visit KidneyHealthGateway.com and find the clinical trial right for you.
This educational content is sponsored by MorphoSys.