What You Should Know About Complement 3 Glomerulopathy (C3G)
- Staff
- 19 minutes ago
- 2 min read
Most people have never heard of C3G kidney disease. Short for complement 3 glomerulopathy, this rare condition can cause inflammation and scarring in the kidneys. C3G can progress to kidney failure if left untreated. The good news? Researchers are making exciting progress in understanding and treating C3G.
What is C3G?
C3G stands for complement 3 glomerulopathy.
Let's break it down:
Complement 3: A protein that plays a role in immunity.
Glomerulopathy: Damage to glomeruli, the small filtering units in the kidney
“Glomerulonephritis can happen for many reasons: autoimmune conditions like lupus, infections, or some cancers,” said nephrologist Dr. Andrew Bomback. “C3G is inflammation or swelling caused by an overactive immune response from the complement system.”
What Causes C3G?
A part of the immune system called the complement system usually helps the body fight infections and remove damaged cells. Sometimes this system goes into overdrive and starts targeting the body, causing C3G. The complement system is an important part of the immune system that helps the body fight off germs and other invaders. It's activated by three immune pathways
Classical Pathway
Triggered when antibodies attach to germs or damaged cells.
Lectin Pathway
Activated when certain proteins in the blood spot sugars on the surface of foreign objects.
Alternative Pathway
Always “on” at a low level, ready to fight germs, but it can cause problems if it becomes overactive.
“In C3G, the alternative pathway goes from low-level activity to hyperactivity,” said Dr. Bomback. “You essentially lose the brakes on the system. ”When the brakes are gone, the alternative pathway makes too many complement proteins. These proteins start to damage the kidneys. This causes inflammation at first,” Dr. Bomback explained, “If left unchecked, that inflammation leads to scarring.”
Types of C3G
C3G is an umbrella term for kidney damage caused by an overactive complement system. There are two types of C3G.
Dense Deposit Disease (DDD)
Deposits of complement protein form in the intramembranous region, a specific layer of the filtering barriers in the kidney.
C3 Glomerulonephritis (C3GN)
Deposits of complement protein form in several parts of the kidney. “We believe DDD is the more aggressive type. It has the fastest rate of kidney failure and often reoccurs quickly after transplant,” said Dr. Bomback. “C3G is also serious, but may progress more slowly.”
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