Complement 3 glomerulopathy (C3G) is a rare kidney disease where a part of the immune system causes kidney inflammation, leading to damage and reduced kidney function. There are two main types of C3G:
- C3 glomerulonephritis (C3GN)
- Dense deposit disease (DDD)
C3GN is the more common type of C3 glomerulopathy, making up about 66% of all C3G cases. Here’s what to know about this type:
What it looks like under a microscope: The deposits of C3 protein under the electron microscope are lighter and less structured compared to those seen in DDD.
Where the deposits are found: These protein clumps often collect in the mesangium, which is the central part of the glomerulus, along with the capillary walls of the kidneys.
Who it affects: C3GN can occur at any age, but it is most often seen in adults.
Characteristics: Although C3GN is a serious condition, it progresses more slowly compared to DDD. People with C3GN are more likely to develop nephrotic syndrome (release of too much protein in the urine) compared to those with DDD.
DDD is the less common type of C3 glomerulopathy, accounting for about 33% of all cases. Here’s what to know about this type:
What it looks like under a microscope: The imaging will show very dark, thick deposits of C3 protein. These deposits most often have a distinctive ribbon-like appearance.
Where the deposits are found: They are inside the kidney’s filtering units, which include the following:
- Glomerular basement membrane
- Bowman’s capsule
- Tubular basement membrane
- Mesangium
In some cases, the deposits occur in both the subendothelial and subepithelial regions of the glomerular basement membrane.
Who it affects: DDD affects mostly children and young adults.
Characteristics: DDD is known to be the more aggressive type. It can progress quickly into kidney failure and may also recur following a kidney transplant.
The two main types of C3 glomerulopathy are categorized based on where and how C3 protein buildup occurs.
The only way to distinguish between the two types of C3G is a kidney biopsy. A kidney biopsy is a procedure where a healthcare provider collects a small sample of kidney tissue and examines it under the microscope.
Although both types of C3G cause similar kidney problems, they show different patterns of C3 deposition under the microscope. This difference in pattern helps determine your C3G type.
Early diagnosis of your type of C3G and treatment is important to prevent a decline in kidney function.
