What is C3 Glomerulopathy?

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.