Complement 3 glomerulopathy (C3G) is a group of rare kidney diseases that is caused by an overactive immune system. With C3G, the body produces too many proteins, leading to kidney damage. The progression of C3G and life expectancy varies from person to person—age, kidney function, and overall health can play a role.
Whether due to genetics, autoimmune issues, or other factors, people with C3G have an overactive complement system (which is part of the immune system). This dysfunctional complement system breaks down too many infection-fighting proteins, and these protein pieces accumulate in the kidneys. This causes damage to the glomeruli, or the kidneys’ filtration systems, leading to kidney issues.
These kidney problems worsen over time. Up to half of adults with C3G may develop end-stage renal disease (ESRD) within 10 years of their original diagnosis. ESRD—also called permanent kidney failure—is a serious, life-threatening condition that occurs when the kidneys cannot meet the body’s needs.
The type of C3G you have can affect your risk of developing ESRD. There are two main types:
- Dense deposit disease (DDD): This type is characterized by long, ribbon-like protein deposits in the kidneys. People with DDD are usually diagnosed as children or adolescents. People with DDD may be at an increased risk of certain C3G complications, including vision problems and issues with fat distribution around the body.
- C3 glomerulonephritis (C3GN): People with C3GN have small protein clumps in the kidneys and are usually diagnosed in adulthood. They are at an increased risk of ESRD as compared to those with DDD. However, the rate of kidney damage and failure is usually slower in people with C3GN than in those with DDD.
Age also appears to play a role. Some research suggests up to 70% of children with C3G progress to ESRD, while about 30-50% of adults do.
Patients are also at a higher risk of ESRD if they have worse kidney filtration function and more protein in their urine when they’re diagnosed.
C3G is a very rare disease, and there is no cure. However, many people can expect to live a typical lifespan with C3G, especially when it is well-managed with treatment.
About half of all patients with C3G end up experiencing ESRD within a decade of their diagnosis; however, the other 50% of patients maintain kidney function for longer.
Once someone has ESRD, they may need to undergo dialysis, a process to remove waste from the body, or they may need a kidney transplant. In people who receive a kidney transplant, about half will see their C3G come back. Only about 35% of people survive with ESRD for at least 5 years.
People with C3G may see a worsened quality of life, particularly if their disease progresses to kidney failure.
It can be a challenge to manage C3G symptoms, which can include blood in urine, swelling, frequent infections, and high blood pressure. Fatigue is also a major concern for the majority of C3G patients—a 2024 study found that up to 77% of participants said they needed to sleep during the day due to their fatigue.
C3G may also cause:
- Pain or discomfort
- Depression
- Anxiety
- Difficulty completing everyday tasks
While there is no cure for C3G, there are treatment options that can help ease symptoms and improve prognosis.
Healthcare providers may prescribe patients medications to control C3G symptoms like high blood pressure and protein in urine, which improves kidney function. But certain diet and lifestyle changes can help, too.
1. Alter Your Diet
Healthy kidneys usually maintain the body’s fluid balance by regulating levels of sodium and other minerals. But when the kidneys can’t balance sodium levels, it’s important to reduce the amount of sodium in your diet to help avoid high blood pressure and further kidney damage.
C3G patients may want to meet with a nutritionist or dietitian to develop a healthy eating plan to protect their kidney function, which might include:
- Reduced sodium intake
- Limited protein intake
- Less potassium and phosphorus
- Avoiding saturated and trans fats
People with advanced C3G or ESRD may need to limit their fluid intake to avoid fluid overload in the body. Talk with your healthcare provider to determine whether you need to monitor how much you drink each day.
2. Keep a Healthy Weight
Maintaining a healthy weight and avoiding obesity can improve kidney health, since extra body weight can put extra stress on the kidneys.
Work with your healthcare team to determine a healthy weight range for your body, as well as a treatment plan to help you reach and maintain it. That may include changes to your diet, activity levels, or prescription medications.
3. Avoid Tobacco
Smoking is dangerous for kidney health and may speed up kidney damage. It also increases blood pressure, which can also contribute to kidney problems.
If you currently smoke, talk with your healthcare team about making a plan to quit.
4. Exercise Often
Engaging in regular physical activity may support a healthy weight and improve kidney health. It can also reduce emotional stress, which may affect kidney health.
Your healthcare team will likely recommend incorporating gentle exercises that will not worsen your daytime fatigue. Consider trying walking, biking, yoga, or swimming to get started.
5. Keep Up With Medical Appointments
C3G is a chronic disease that requires regular follow-up care from your healthcare team. See your provider regularly to check your blood pressure, monitor lab values, and address any complications or treatment side effects. Take your medications as prescribed to slow the rate of kidney damage from C3G.
As C3G progresses, it can cause worsening high blood pressure, urine changes, and other issues. Fatigue and mental health symptoms can also affect your quality of life.
A team of healthcare professionals can help you find lifestyle changes or medications that help you manage these symptoms and slow kidney damage. That could include exercising and eating healthy, meeting with a support group, and scheduling breaks throughout the day to avoid overexerting yourself.
