What is C3 Glomerulopathy?
C3 Glomerulopathy (C3G) is a rare disease of the kidneys caused by a fault in the complement system.
Complement is part of your body’s normal immune response to bugs.
Your body has an in-built system of protector proteins that stop complement from attacking your own cells.
In C3G this system fails.
This causes complement – primarily the complement protein C3 – to be deposited in the filtering part of the kidney called the glomerulus
The damage to this part of the kidney can lead to abnormal kidney function and leaking of blood and protein into the urine.
Over time, this can lead to end-stage kidney disease.
What are MPGN, C3GN, DDD?
Membrano-Proliferative Glomerulonephritis (MPGN) refers to a group of diseases based on how the kidney looks under a microscope. In MPGN the kidney is damaged by deposits of immune substances in the glomerulus.
These deposits can be immunoglobulins, complement or a mixture of both.
Where the deposits are predominantly complement and are thought to be caused by abnormal activity in the complement system this is known as C3 Glomerulopathy.
The terms C3 Glomerulonephritis (C3GN) and Dense Deposit Disease (DDD) are sub-groups of C3G and are distinguished by the way in which the complement deposits are seen on a biopsy.
In C3GN the deposits tend to appear patchy.
In DDD the deposits are seen more as long thick strips of complement.
Why does C3G happen?
Patients may develop autoantibodies to the complement proteins. These autoantibodies then attack the protein and stop it from doing its job.
There may also be a genetic fault in the complement system or the protector proteins that allows complement to be deposited in the kidney.
How does C3G present?
The damage to the kidney caused by C3G can lead to abnormalities in the urine and/or kidney function.
If lots of protein is leaking from the kidneys, the urine can become frothy and there can be fluid retention and swelling of the legs, arms and face.
Sometimes, blood might be seen in the urine.
Sometimes, only a small amount of blood and/or protein is leaking from the urine that cannot be seen, or there is a gradual fall in kidney function. In these cases, the problem might not be found until a blood or urine test is done for an unrelated reason such as a routine medical examination.
Once these problems have been found, you will then be referred to a kidney specialist.