Membranous nephropathy, also called membranous glomerulonephritis, is a rare kidney disease that affects the filters, or glomeruli, of your kidneys. These filters usually help remove waste and fluids.
But when the glomeruli become inflamed, your kidneys may swell and stop working properly. The filters can fail to keep protein out of your urine, which can lead to problems in other body functions. Doctors call this condition nephrotic syndrome.
Types of Membranous Nephropathy
There are two types of membranous nephropathy.
Primary membranous nephropathy. This type happens by itself and directly involves the kidneys. You may hear this type referred to as idiopathic.
Secondary membranous nephropathy. This type happens when you have some other bodily problem that has affected your kidneys.
Membranous nephropathy is an autoimmune disease, and it is chronic. But it is also rare: about eight to 10 out of every million people get this disease.
Causes of Membranous Nephropathy
The glomeruli have a layer of tissue, or membrane, that helps filter waste and fluid from your blood. Membranous nephropathy is caused by a thickening of this membrane.
It’s not clear why this thickening happens, but it is caused by immune cells. In primary membranous nephropathy, your body makes antibodies, or protective proteins, that target proteins for your kidneys.
This leads to a deposit of immune cells in your kidney filters that cause inflammation and thickening. The thickening stops your kidneys from working, which causes you to lose a lot of protein through your urine.
Secondary membranous nephropathy is caused by other health problems or treatments that affect the kidneys. These can include:
- Rheumatoid arthritis
- Sjorgen syndrome
- Heavy metal poisoning
- Nonsteroidal anti-inflammatory drugs
- Hepatitis B
- Hepatitis C
- Cancer, especially lung and colon cancers
Anyone can get membranous nephropathy, but it’s more common in older Caucasian men. Children rarely get this kidney condition, and it’s less common in women.
Symptoms of Membranous Nephropathy
Symptoms of membranous nephropathy can be different for everyone. Some symptoms are:
- Foamy or frothy urine
- Weight gain
- Poor appetite
- Blood pressure problems
- Peeing a lot
- Peeing less
- Shortness of breath
- Trouble breathing
Swelling is often the first thing people notice. It usually starts in your feet, ankles, and legs and then moves to the rest of your body.
The loss of protein causes swelling. As you lose protein, fluid leaks out of your blood vessels into your tissues, which causes fluid buildup. Sometimes fluid can gather in your lungs, which might make it hard to breathe.
Diagnosing Membranous Nephropathy
Your doctor will do a physical exam and run some tests.
Urine test. Urine tests will check to see how well your kidneys are working. This test will look for levels of:
Blood test. A blood test is used to look for antibodies and other conditions. Your doctor might order a blood test to check for infections and for levels of:
Imaging. Your doctor might do an ultrasound, a CT (computed tomography) scan, or an MRI (magnetic resonance imaging) to look at your kidneys. This will help find any damage and rule out other possibilities.
Kidney biopsy. Medical professionals will do surgery to take a small piece of your kidney. They will examine the cells and confirm the diagnosis.
Complications of Membranous Nephropathy
Membranous glomerulopathy can lead to other symptoms and health conditions. These include:
Membranous Nephropathy Treatment
There is no cure for membranous nephropathy. Your doctor will focus on treating your symptoms and making your immune system stronger. Treating underlying conditions can also help.
Your doctor might give you medications. These can include:
- ACE (angiotensin-converting enzyme) inhibitors
- ARBs (angiotensin receptor blockers)
- Blood thinners, if you have a risk of blood clots
Your doctor might also recommend lifestyle changes and vitamin supplements. These include:
- Low salt diet
- Low protein diet
- Vitamin D supplement
- Calcium supplement
If you have chronic membranous nephropathy that doesn’t respond to treatment or that causes lots of damage, your doctor might recommend a kidney transplant.
For most people, the goal is to control symptoms and slow down the disease. Some people will respond well to conservative treatment. Up to one-third of patients see their symptoms stop (go into remission) within five years even without immune system treatment.
If you have membranous nephropathy and notice changes in your health, or you start to see swelling or other symptoms, make sure you talk to your doctor.