Complement 3 glomerulopathy is a group of conditions that affect your immune system and prevent your kidneys from filtering blood as well as they should. Most cases of C3G don’t have a clear cause, but gene mutations and autoantibodies may be responsible. There isn’t a cure, but treatment options exist to help slow it down and reduce your symptoms.
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Complement 3 glomerulopathy (C3G) is a group of conditions that affect how well your kidneys work. Your kidneys filter your blood and remove waste and extra water to make urine (pee).
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Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
“Complement 3” refers to a protein in your blood that’s important to your immune system. “Glomerulopathy” (pronounced glo-MARE-yoo-LOP-uh-thee”) refers to damage in your glomeruli (pronounced “glo-MARE-yoo-lye”). Glomeruli are groups of tiny blood vessels in your kidneys that help filter your blood and make pee.
Before 2013, healthcare providers used the terms “membranoproliferative glomerulonephritis (MPGN) type I, II or III” or “mesangioproliferative glomerulonephritis.” However, they now use C3G to classify the group of conditions.
There are two types of C3G. Healthcare providers determine the type according to what kind of damage and inflammation your glomeruli have when providers look at kidney tissue samples under a microscope. The two types are:
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Yes, C3G is a chronic condition. That means the condition slowly gets worse over time.
C3G is very rare. Healthcare providers estimate it affects 2 to 3 out of every 1 million people.
Common symptoms of both types of C3G include:
Both types of C3G can also cause kidney failure. Some kidney failure symptoms include:
C3G may also cause symptoms that don’t affect your kidneys or how they function. These symptoms may include:
Complement 3 glomerulopathy occurs when your complement system stops working the way it should. Your complement system consists of proteins in your blood that are part of your immune system. It helps enhance (complement) your immune system by fighting foreign invaders like bacteria and viruses.
If you have C3G, your complement system works harder than normal, which damages your complement 3 (C3) proteins. Damaged parts of your C3 proteins trap themselves in your glomeruli, which makes it harder for your glomeruli to filter your blood or create pee. Without treatment to help slow down the damage, C3G will continue to damage your kidneys and affect your kidney function. This can lead to kidney failure.
In most cases of C3G, healthcare providers aren’t sure what exactly causes your complement system to stop working as it should. However, in some cases, mutations in your C3, CFH and other complement system genes cause C3G. And monoclonal gammopathy may also indirectly cause a kidney injury that impairs the alternative pathway (AP) of complement, which could cause C3G. Monoclonal gammopathy is a blood disorder that affects the plasma cells in your bone marrow.
Medical researchers suspect that autoantibodies may also affect your complement system. Autoantibodies are proteins your immune system makes that target normal body tissues by mistake. There isn’t enough research to be sure that autoantibodies definitively cause C3G.
Complement 3 glomerulopathy can affect anyone. It equally affects men and people assigned male at birth (AMAB) and women and people assigned female at birth (AFAB). The average age of diagnosis is 23. DDD tends to appear at a younger average age than C3GN.
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Approximately 50% of people with C3G develop kidney failure within 10 years of diagnosis.
A healthcare provider may use various tests to evaluate your kidneys’ health and effectiveness. These tests may include:
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Currently, there isn’t a cure for C3G. However, healthcare providers and medical researchers are studying the disease and conducting trials in the hope of finding a cure.
There are currently no United States Food and Drug Administration (FDA)-approved treatment options specifically for C3G. However, healthcare providers may prescribe a number of treatments or supportive therapies to slow the progression of C3G and manage your symptoms. These may include:
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If you have DDD or C3GN and also have monoclonal gammopathy, a provider will recommend further evaluations to check for underlying conditions.
You can’t prevent C3G.
About half of people who have C3G develop kidney failure within 10 years of diagnosis. There isn’t a cure for kidney failure. However, with proper diagnosis and treatment, you may still live a long life without many drastic changes to your quality of life.
If you have C3G, healthcare providers will work with you to develop the best treatment plan, which may include medications, supportive therapies and changes to your lifestyle. Your treatment plan may include:
Contact a healthcare provider if you have symptoms of C3G, including any changes to your pee. These may be signs that your kidneys aren’t working as they should.
If you have C3G, make sure your provider refers you to a kidney specialist who diagnoses and treats conditions that affect your kidneys (nephrologist).
A note from Cleveland Clinic
Complement 3 glomerulopathy affects the tiny filtering units in your kidneys. If you have C3G, you may notice changes in your pee, swelling, joint pain, vision problems and fatigue.
You may feel a wide range of emotions as you accept your diagnosis and adjust to how C3G affects your life. Give yourself time and space to learn about C3G and your treatment options. Learning about your options and what to expect can help you accept your emotions in healthy and productive ways. Providers are available to you to offer information and guidance. Talk to them if you have any questions or need advice or support.
Last reviewed on 06/10/2023.
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