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Complement 3 Glomerulopathy (C3G)
Complement 3 Glomerulopathy (C3G) is a rare, chronic kidney disease. It damages the glomeruli, the tiny filtering units in the kidneys that help remove toxins from the blood. “Complement 3” (C3) refers to a blood protein that is part of the body’s alternative complement system. The complement system is a group of proteins in the blood that helps the immune system work correctly. Usually, it serves as a first line of defense to protect our bodies from infection.
C3G occurs when the alternative complement system overactivates. The result is inflammation, glomeruli injury, hematuria (blood in the urine) and proteinuria (protein in the urine). The overactivation of the complement system typically causes chronic kidney damage over time. Approximately half of people with C3G progress to kidney failure in 10 to 15 years.
Medically reviewed by Dr. Corey Cavanaugh, D.O.
Who Gets C3G
C3G affects one to two people out of every one million people in the U.S. It can affect people of all ages but typically is diagnosed in people who are in their 20s and 30s.
Sometimes, genetic changes in specific proteins cause C3G. This is true for about 10 to 25% of people with C3G. Researchers are still studying what causes C3G in other people with the disease.
Types of C3G
C3G is a specific type of MPGN, of which there are two varieties:
DDD
Dense Deposit Disease (DDD)
C3GN
C3 Glomerulonephritis
(C3GN)
Signs and Symptoms
Some symptoms of C3G include:
- Blood in urine (hematuria)
- Dark urine
- Decreased urine volume
- Fatigue
- Foamy urine
- High blood pressure (hypertension)
- High creatinine levels in the blood
- High protein levels in urine (proteinuria)
- Low protein levels in the blood (hypoalbuminemia)
- Swelling in many areas of the body (edema)
- Vision difficulties
Of note, children and young adults, can present with these symptoms following an upper respiratory tract infection.
Diagnosing C3G
To diagnose C3G, doctors perform a kidney biopsy and order blood tests. A kidney biopsy involves removing a tiny portion of the kidney tissue and testing it in the lab.
Other tests may include:
- Blood tests to reveal the presence of albumin, cholesterol, creatinine, protein and many other components in the blood.
- A glomerular filtration rate (GFR) calculation to estimate your kidney function. You can calculate your GFR if you know your blood creatinine and urine protein levels.
- Ultrasound to provide a closer look at the kidneys
Your Treatment Options
Researchers have not yet discovered a cure for C3G. Treatment focuses on minimizing or stopping protein in the urine. The less protein in the urine, the better people with C3G will do. Treatment also includes managing side effects of C3G, such as high blood pressure. Your doctor will prescribe medicines for you based on your needs. Medications may include ACE inhibitors or Angiotensin receptor blockers for blood pressure control, and medications to suppress the immune system, like corticosteroids and mycophenolate mofetil.
People with C3G respond differently to treatment. Children with C3G tend to respond better than adults.
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.
Some clinical trials enroll patients, based on their genetic testing results, to test the effectiveness of precision-based therapies targeted to specific genetic changes.
Tips For Living With C3G
Your care team can help you manage your condition.
Find an Exercise You Enjoy
Regular, moderate activity helps manage your blood pressure and weight and improves your overall well-being.
Follow Your Treatment Plan
Follow your doctor’s instructions and take your medicines as prescribed.
Work With Your Care Team
See your nephrologist routinely for tests and to learn more about how to manage your health.
Your Nephrologist May Also Recommend
1
Diuretics
Diuretics help manage fluid retention and edema, common complications of C3G.
2
Anticoagulants
Anticoagulants are essential for people with rare kidney diseases. They prevent the formation of blood clots.
3
Medications
Blood pressure medicines help lower your blood pressure. Statin medicines can reduce your cholesterol level.
4
Vitamins
Vitamins are crucial in supporting overall health and lowering the risk of complications.
Kidney Transplant and C3G
Kidney transplantation is an option for people who develop kidney failure due to C3G. After the transplant, doctors use a transplant kidney biopsy to check whether the disease has returned.
Unfortunately, the risk of recurrence after a transplant is high. About two-thirds of people who have a kidney transplant due to C3G get the disease again. In about half of people who have a kidney transplant for C3G, the transplanted kidney fails. They must return to dialysis or consider having another kidney transplant.
