Complement 3 glomerulopathy (C3G)

C3G and kidney disease
Learn about the causes, symptoms and treatments of C3 glomerulopathy (C3G). C3G is a disease that causes inflammation and damage to the filters of your kidneys.

What is C3 glomerulopathy?

C3 glomerulopathy (glo-mer-u-lop-a-thy) is a disease that affects how well your kidneys work. It causes damage to structures in the kidneys called glomeruli (glo-mer-yuh-lahy). Glomeruli help the kidneys filter toxins out of your blood. Kidney damage from C3 glomerulopathy can be serious and lead to kidney failure. C3G is typically diagnosed in children and young adults, however it can be diagnosed at any age. 

There are two types of C3 glomerulopathy: dense deposit disease (DDD) and C3 glomerulonephritis (C3GN). Only a kidney biopsy can differentiate between these two diseases. There are two different patterns of damage in the glomeruli, the tiny filters in your kidneys that clean your blood. The difference in the type of damage and inflammation in the kidney tissues looks different under a microscope. Both types cause similar kidney problems. While some studies suggest DDD patients have a more severe course, it is important to understand that both DDD and C3GN can lead to kidney failure.

What causes C3 glomerulopathy?

The "C3" in C3 glomerulopathy refers to a protein (called C3 complement protein) that is part of your body's complement system. The complement system is a collection of proteins in your blood that help (complement) your immune system. In C3 glomerulopathy, the complement system becomes overactive or doesn't work as it should. The overactive complement system leads to damage and inflammation of the glomeruli (which help the kidneys filter toxins out of your blood).  

There are two reasons why the complement system is overactive in C3 glomerulopathy: 

  1. Due to genetic changes in certain proteins: Some proteins in the complement system help control (regulate) and stop the system when needed, other proteins may accelerate (or speed up) the complement system. Genetic changes can occur in either the proteins that help regulate the system or proteins that accelerate (or speed up) the complement system, both can make a patient more likely to develop C3G.  
  2. Due to autoantibodies: Autoantibodies are abnormal proteins that can also change the ability of proteins to control the complement system. 

What are the signs and symptoms of C3 glomerulopathy? 

The kinds of symptoms, and how bad they are, can be different for everyone. People with C3 glomerulopathy may not notice symptoms until the disease gets much worse. 

Some signs and symptoms of C3 glomerulopathy are: 

C3 glomerulopathy can also cause symptoms that are not related to your kidneys. These include: 

  • Eye problems 

  • Unusual distribution of fatty tissue under the skin 

Many people with C3G report that fatigue is the symptom that impacts them the most. Here are some ways to cope with this symptom: 

  • Plan ahead – you can plan activities for times when you are likely to have more energy, and plan to rest when you will have less energy. 

  • Spread tasks out over the week and do a little bit each day. 

  • Sit down to do chores whenever you can such as folding laundry, chopping vegetables or other stationary tasks that are easier to do while sitting in one place. 

  • Ask family and friends for help with your everyday activities, such as housekeeping, shopping, and cooking. 

  • Talk with your employer to find ways to save energy during work.

How can doctors tell if I have C3 glomerulopathy?

If doctors find high levels of protein in your urine after a urine test, they may suspect a kidney-related disease. Since the symptoms of C3 glomerulopathy are similar to symptoms of other kidney-related diseases, the only way for doctors to know if you have C3 glomerulopathy is with a kidney biopsy. A kidney biopsy is a procedure where doctors take a tiny piece of your kidney tissue to look at it under a microscope. 

With a kidney biopsy, doctors will also be able to tell if you have C3G, or another kidney disease. 

Not all doctors may be as knowledgeable about C3G as others. If you don't feel comfortable with your doctor's knowledge about C3G, you can ask for a referral to a specialist or reach out to other doctors.

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How do doctors treat C3 glomerulopathy?

There is currently no cure for C3 glomerulopathy. The goal of treatment is to slow the damage to your kidneys and delay or prevent kidney failure. Your doctor will work with you to make a treatment plan. 

Doctors may treat C3 glomerulopathy with medicines that: 

  • Help control your blood pressure 

  • Suppress (weaken or slow) the immune system  

Doctors may also recommend that you: 

  • Regularly follow up with a nephrologist (kidney doctor) and get kidney function tests checked frequently. Learn more about kidney function tests that your doctor may order such as blood tests, urine tests, kidney ultrasound and kidney biopsy.  

  • Make changes to what you eat  

  • Get evaluated for dialysis or a kidney transplant depending on the level of your kidney function

For some patients, your kidneys may get worse over time and lead to kidney failure. If your kidneys fail, you'll need to start dialysis, a treatment to remove waste and fluid from your blood, or receive a kidney transplant.

Do I need to make changes to what I eat if I have C3 glomerulopathy?

What you eat and drink is very important when you have kidney disease. There are many things to consider depending on your stage of kidney disease, such as: 

  • How and what you eat  

  • Different nutrients 

  • The amount of fluid you consume 

A dietitian (an expert on food and nutrition) can help you make a kidney-friendly eating plan that works for you. You can find more information about eating healthy with kidney disease at Kidney Kitchen®. 

Your doctor may also recommend that you: 

  • Make changes in what you eat to lower the amount of protein, fat, sodium and cholesterol you take in 

  • Take in more or less fluids through drinks and some foods  

  • Lose weight 

How does C3 glomerulopathy affect mental health?

Living with C3 glomerulopathy can affect your mental and emotional health. Depression, anxiety and other mental health issues are common in people with kidney disease. If your kidney damage gets worse, you may feel more stress. For example, if you are on dialysis, stressors may include: 

  • Cost of dialysis 

  • Time needed for dialysis 

  • Feeling like a burden to others 

  • Changes in your job 

  • Limits on what you can eat 

  • Fear of pain 

Find healthy ways to cope 

It is normal to have stress, anxiety and depression when having a health problem. If you notice changes to your mental health, these activities may help you feel better: 

  • Be active for at least 30 minutes most days of the week. Exercise can lower feelings of depression and anxiety and improve the way you think, learn and remember things. 

  • Get enough sleep. Aim for 7-8 hours a night and try to go to sleep and wake up at the same time every day. Poor sleep affects mood, energy, attention span and your ability to think clearly. 

  • Tap into your faith. For some, connecting with religion and spirituality may serve as a valuable way to cope with mental health issues. Your faith community can provide a group of people that you can rely on when you are feeling down. 

  • Explore your creative side. Pick up an old hobby or try something new such as painting, crafting or sewing. When engaged in something you enjoy, it can lower stress and release feel-good chemicals in your brain. 

Talk to a professional 

If you want to talk to a professional, ask a member of your treatment team for a referral to a mental health therapist, counselor or social worker.  

These professionals are trained to help you:  

  • Understand and process your emotions 

  • Improve your coping skills  

  • Maintain healthy relationships with loved ones  

  • Navigate everyday life with chronic disease 

  • Advocate for your needs 

Many health insurance providers cover mental health services. Call your health insurance provider to find out what your health insurance plan includes and get a list of in-network mental health providers in your area. 

Find a support group 

Having a chronic disease like C3 glomerulopathy can feel isolating. But you are not alone. One of the best ways to cope with a major life change is to connect with people who are going through a similar experience.   

Benefits of joining a support group include:  

  • Being able to talk openly and honestly with people who understand what you are going through 

  • Learning tips for managing C3 glomerulopathy from people who have been living with it for longer than you 

  • Learning more about C3 glomerulopathy and opportunities for patients 

  • Finding new ways to cope 

  • Feeling empowered and supported by your new community 

  • Making new friends 

You can find a C3G support group through Facebook. Visit the C3G Warriors page.  

Learn more about mental health and kidney disease and where to go for support. 

How to care for someone who has been diagnosed with C3 glomerulopathy?

Being a caregiver for someone with C3G is a big job as they will need additional care with daily living along with their medical appointments. This is an important role and can often mean you help to assist in day-to-day activities such as assisting with household chores like making healthy meals to preparing for and attending medical appointments with them along with helping to coordinate care and advocating on their behalf.  

Checking in on their emotional health is also important along with keeping an eye on yourself. Many caregivers can experience burnout, but it's important to take care of yourself too. If you are experiencing burnout, seek support from other caregivers and fit in time for breaks to rest in your schedule. Learn more about tips for caregivers.

Where can I learn more about C3 glomerulopathy research? 

If you or a loved one has been diagnosed with C3G, learning more about research may bring hope. 

  • Visit PubMed to find articles about the latest in C3G research. 

  • Kidneeds is a nonprofit organization that hosts an annual C3G Family conference with the University of Iowa. This conference offers community, support, and the opportunity to learn about the latest treatments and research in C3G. 

Education content supported by Novartis