Complement 3 Glomerulopathy


C3G stands for Complement 3 Glomerulopathy, a very rare and chronic disease that causes the kidneys to not work properly. C3G used to be called Membranoproliferative Glomerulonephritis (MPGN) 1, 2, or 3, but healthcare professionals have changed how they classify and talk about this disease. The C3 refers to a key blood protein that plays an important role in your immune system. The G stands for glomerulopathy, or damage to the filtering units of the kidney (the glomeruli).

Who Gets C3G

C3G affects 2-3 individuals out of every 1 million people. It affects people of all ages, but the IC-MPGN form tends to be more common in children than adults.

C3G occurs when a part of your immune system called “the complement system” becomes overactive or dysfunctional.

Types of C3G

Between 10-25% of all C3G diagnoses are genetically linked. There are three types of C3G:


Immune-complex MPGN (IC-MPGN) [formerly called MPGN 1]


Dense Deposit Disease (DDD) [formerly called MPGN 2]


C3 Glomerulonephritis (C3GN) [formerly called MPGN 3]

Signs and Symptoms

Physician experts believe that when complement proteins like C3, which are part of your immune system, are not well-controlled, it results in damage to the kidneys’ filtering units.

Some symptoms of C3G include:

  • High levels of protein in urine (proteinuria) 
  • Blood in urine (hematuria) 
  • Low levels of protein in the blood (hypoalbuminemia) 
  • Swelling in many areas of the body (edema) 
  • Fatigue 
  • Dark and/or foamy urine 
  • High blood pressure (hypertension)
  • Decreased urine output 
  • High levels of creatinine in the blood
  • Vision difficulties

Diagnosing C3G

To diagnose C3G, doctors examine a tiny portion of the kidney tissue in a procedure called a biopsy AND conduct blood tests to look at levels of specific complements, including C3, C4, and C5.

Other diagnostic tools may include:

  • 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

Your Treatment Options

There are currently no FDA-approved medicines to treat C3G. 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.

Standard first-line (initially prescribed) treatments for C3G are blood pressure medications, like lisinopril and ibesartan, and immunosuppressants, like steroids and mycophenolate mofetil (MMF or CellCept).

Patients have varying degrees of success with these forms of medical treatments. Children with C3G tend to be more responsive to treatment than adults.

Headline decoration line

Clinical trials are another treatment option.

Your doctor helps you find the right study for you. These trials test more targeted treatments with potentially lower risks of side effects.

There are many new, potential treatment options based on new understanding of C3G that are being studied in clinical trials right now. All treatment options being studied are complement-targeted therapies that specifically target areas of the alternative pathway, rather than the classical pathway, to stop progression of the disease. 


Tips For Living With C3G

Patients with C3G benefit from supportive measures including:


Regular, moderate activity helps manage your blood pressure and weight and improves your overall well-being.

Prescription Regimen

Follow your doctor’s instructions and take your medicines as prescribed.

Regular Check-Ups

See your doctor as scheduled to monitor your kidney function and quickly address any changes.


Get help coping with the challenges of living with C3G through support groups. Connect with others who understand your journey, share experiences, and find comfort in knowing you’re not alone.


Eating a kidney-friendly diet can help manage the symptoms and progression of your RKD. Learn more about a kidney-friendly diet and get our cookbook.

Your Nephrologist May Also Recommend



Diuretics are important as they help manage fluid retention and edema, which are common complications of kidney dysfunction.



Anticoagulants are essential for rare kidney disease patients to prevent the formation of blood clots.



Blood Pressure medications to lower high blood pressure. Statins to lower the cholesterol level.



Vitamins play a crucial role in supporting overall health and mitigating potential complications.

Related Resources


U: A C3G Update Webinar

Educational Materials

What is Clinical Research?

Informational Documents

Patient Empowerment Flyer

Fact Sheet

C3 Glomerulopathy (C3G)


Sign up to get NephCure’s latest updates.

This field is for validation purposes and should be left unchanged.