Primary Immune Complex Membranoproliferative Glomerulonephritis (IC-MPGN) 

What causes IC-MPGN?

IC-MPGN develops when immune complexes build up in the filters of the kidneys. These buildups activate the complement system, a part of the immune system, which normally protects your body from invaders like germs and fungus. When it becomes overactive or doesn't work as it should, your immune system can attack healthy body tissues causing inflammation and kidney damage

Doctors classify IC-MPGN based on whether a cause can be identified. There are two types of IC-MPGN, primary and secondary.  

What causes primary IC-MPGN?

Primary IC-MPGN is diagnosed when testing does not identify another condition or disease causing the immune-complex deposits in the filters of the kidneys. It happens without a known underlying cause or reason. 

What causes secondary IC-MPGN?  

Secondary IC-MPGN happens when another condition is triggering the immune-complex deposits. Causes can include:  

• Infections, including hepatitis B, hepatitis C, and certain chronic bacterial infections.  
  • Autoimmune diseases cause the immune system to attack your body. This can include diseases like lupus, Sjogren's disease and rheumatoid arthritis. 
  • Certain blood or bone marrow disorders or conditions that make abnormal antibodies. 

Who is at risk for primary IC-MPGN?  

Primary IC-MPGN is very rare, so it is hard to know who may be at risk. It can affect both men and women and is generally found when people are children or young adults, but it's possible to be diagnosed later in life.  

Because primary IC-MPGN means that no underlying cause has been found, there may not be a specific risk factor that explains why a person develops the disease.

How will I know if I have primary IC-MPGN?  

Doctors use blood and urine tests to check for signs of kidney damage and measure how well your kidneys are working to filter your blood. These tests look at your kidney function by checking for protein or blood in the urine, measuring your estimated glomerular filtration rate (eGFR) and checking levels of complement proteins in your blood. If these tests suggest kidney damage, your doctors may recommend additional testing.

A kidney biopsy is required to diagnose IC-MPGN. During a kidney biopsy, your doctor will take a small piece of kidney tissue to look at it under a microscope. Special tests can identify patterns of kidney damage and the types of immune proteins that are deposited in your kidney filters or glomeruli.  

Your doctor will likely ask you about underlying causes or recent illnesses, such as infections, autoimmune diseases or other chronic diseases, to rule out secondary IC-MPGN. If no underlying cause is known after a thorough evaluation, the disease may be diagnosed as primary IC-MPGN.

How do doctors treat primary IC-MPGN?  

There is no cure for primary IC-MPGN, but treatment can help protect your kidneys. Treatment canalso focus on slowing the damage to your kidneys and delaying or preventing kidney failure, controlling your immune system and changing some lifestyle habits.  

In 2025, the Food and Drug Administration (FDA) approved pegcetacoplan (Empaveli ®) as the only treatment to reduce protein in urine and the loss of kidney function adults and children ages 12 and older with primary IC-MPGN. Talk with your doctor and healthcare team to learn more about whether this treatment may be right for you.  

Pegcetacoplan is a complement inhibitor, which means it blocks part of the complement system involved in inflammation and kidney damage. Complement inhibitors can increase the risk of certain serious infections. Your healthcare team will discuss vaccines and other steps that may be needed before and after treatment.

Other medicines may be used to help manage the symptoms of primary IC-MPGN, which may include ACE inhibitors and ARBs to control high blood pressure. You may also be prescribed medicines to keep your cholesterol at a healthy level.  

Medicines to help control your immune system include immunosuppressants and steroids to lower immune system activity.  

Along with medicines, your doctor may recommend that you:

• Eat kidney-friendly foods
• Limit sodium based on your healthcare team's recommendations
• Stop drinking alcohol
• Stop using tobacco
• Stay active as recommended by your healthcare team  
• Maintain a healthy blood pressure
• Take your medicines as prescribed

To monitor your kidney function over time, your doctor may recommend that you:

• Follow up regularly with your nephrologist (kidney doctor) and have your blood and urine tests to track your kidney function and the amount of protein in your urine regularly.  
• If your kidney function becomes severely reduced, your healthcare team may talk with you about treatments for kidney failure. This includes dialysis or evaluation for a kidney transplant depending on the level of your kidney damage.

What are the complications of IC-MPGN?  

Primary IC-MPGN can cause ongoing inflammation and scarring in your kidneys. It is a progressive disease, which means that over time, as the disease remains active it may lead to  kidney damage and chronic kidney disease (CKD). In the early stages of CKD, you may not notice any symptoms, and your treatment may involve medicines and lifestyle changes to help protect kidney function. In some people, IC-MPGN will eventually lead to kidney failure, or end stage kidney disease.

Treatment aims to reduce disease activity, protect kidney function and lower the risk of progressing or worsening.  

Each person's disease moves at a different pace, so there is no one timeline that IC-MPGN will follow. Some people may have relatively stable kidney function, while others may have worsening kidney function over time.

If your kidneys fail, treatment options include dialysis or kidney transplant. For some people who do not want transplant or dialysis, conservative kidney management may be an option.

Talk with your doctor about your risk for kidney failure and what steps you can take to help protect your kidney health.

What is the outlook of IC-MPGN?  

The outlook for Primary IC-MPGN depends on how early it is diagnosed and varies from person to person. If there is a lot of kidney damage, you are more likely to progress to kidney failure. Regular tests can help you and your doctor track how much damage is being done to your kidneys and knowing how much protein is leaking into your urine as well as how your disease responds to treatment can affect your long-term kidney health. Talk to your healthcare team about how often you should have kidney testing done.  

Primary IC-MPGN is a rare disease, and it's possible that your nephrologist may not have treated many people with it before. If you have questions about your doctor's experience with primary IC-MPGN, you can ask whether seeing a nephrologist or kidney center with experience treating rare glomerular disease would be helpful.  You can ask for a referral to a specialist or reach out to other doctors.

Primary IC-MPGN can often come back or recur after a kidney transplant. If you are being evaluated for a kidney transplant or have already received one, talk with your transplant team about your risk and how they will monitor the health of your transplanted kidney.  

Living with a rare kidney disease can be difficult at times. Learning about your condition and taking an active role in your care can help you make informed decisions with your healthcare team and lead to better outcomes and quality of life.