C3G kidney disease: How is it diagnosed and how is it treated?

Complement 3 Glomerulopathy, most commonly shortened to C3G or C3G kidney disease, is a rare type of kidney disease that has only been diagnosed since 2013. “C3” refers to a blood protein that has a vital role in the immune system, and “G” is for the damage to glomeruli in the kidneys. 

While all types of kidney disease are serious, C3G is unique because there is currently no treatment available for the condition. Researchers are working to learn more about this rare disease through ongoing research studies in the hopes that they will be able to one day discover a breakthrough. 

To increase awareness around C3G kidney disease, we have a brief guide below about what it is, how it is diagnosed, and how it is treated. Keep reading to learn more.

What is C3G?

The complement system is a collection of proteins in the blood that help the immune system fight bacteria and viruses. If the complement system becomes overactive, normal complement proteins (such as C3) can be broken down. The breakdown of these products can then become lodged in the kidneys, causing irritations that injure the glomeruli and interfere with their ability to filter the blood. Before 2013, patients with this condition would have been diagnosed with “membranoproliferative glomerulonephritis (MPGN)” or “mesangioproliferative glomerulonephritis,” but these terms have since been updated to C3G.

How C3G kidney disease is diagnosed

While a C3G diagnosis requires a kidney biopsy to be confirmed, because it is such a rare disease, doctors will typically run a series of tests to rule out other causes beforehand. Before ordering a biopsy, a medical provider will typically perform a urinalysis, do a blood work panel, perform an ultrasound, and run tests that estimate kidney function. If these still indicate that C3G is a possibility, a biopsy will be performed to look for dense deposits of the complement protein C3 in the kidney tissue.

A look at C3G treatment

Currently, there are no FDA-approved treatments designed specifically for C3G. The treatments currently available to patients are aimed at managing blood pressure, proteinuria, and cholesterol levels low, in addition to controlling the immune system. In some cases, the cause of C3G is able to be identified, which can help doctors determine the best course of treatment.

Autoantibody C3G treatment

Sometimes, C3G is caused by an autoantibody that attacks the complement system and causes the condition. In these cases, immunosuppressants can be used in an attempt to stop the immune system from hindering the complement system.

Genetic mutation C3G treatment

In the event of C3G caused by genetic mutations, plasma infusion and plasma exchange can sometimes be a treatment option — but unfortunately, these interventions tend to only help a select few patients. Plasma infusions can replace missing proteins in the blood, so if a patient is missing the protein that prevents C3G, this may be an option. Plasma exchange removes harmful proteins and replaces them with normal ones.

While there are currently limited kinds of treatment for C3G patients, clinical trials can be an option for patients today. These trials help science move forward and can provide individuals with potential new treatments before they’re on the market. Search available trials today to learn more.