How is C3 Glomerulopathy C3G diagnosed?

C3 Glomerulopathy (C3G) is a rare kidney disorder characterized by abnormal deposits of a protein called C3 in the glomeruli, which are the tiny blood vessels in the kidneys responsible for filtering waste and excess fluid from the blood. The diagnosis of C3G involves a combination of clinical evaluation, laboratory tests, and kidney biopsy.

Clinical evaluation: The first step in diagnosing C3G is a thorough medical history and physical examination. The healthcare provider will ask about symptoms such as blood in the urine, swelling, high blood pressure, and decreased urine output. They will also assess the patient's overall health and look for any underlying conditions that may contribute to kidney damage.

Laboratory tests: Several blood and urine tests are performed to evaluate kidney function and identify any abnormalities. These tests may include:

• Urinalysis: A sample of urine is analyzed for the presence of blood, protein, and other substances.


• Blood tests: These measure levels of creatinine, a waste product that indicates kidney function, as well as complement proteins, including C3 and C4.


• Genetic testing: In some cases, genetic testing may be recommended to identify specific gene mutations associated with C3G.

Kidney biopsy: A kidney biopsy is the most definitive diagnostic test for C3G. It involves the removal of a small piece of kidney tissue for examination under a microscope. The biopsy helps determine the extent of C3 deposits in the glomeruli and assesses the overall condition of the kidneys. It can also differentiate between different subtypes of C3G, such as dense deposit disease (DDD) and C3 glomerulonephritis (C3GN).

Immunofluorescence microscopy: This technique is often used to analyze the kidney biopsy sample. It involves staining the tissue with fluorescent antibodies that specifically bind to C3 and other complement proteins. The pattern and intensity of staining can provide valuable information about the presence and distribution of C3 deposits.

Electron microscopy: Electron microscopy allows for a more detailed examination of the kidney tissue at the ultrastructural level. It can reveal the characteristic dense deposits of C3 in DDD or other structural abnormalities in C3G.

Overall, the diagnosis of C3G requires a comprehensive approach involving clinical evaluation, laboratory tests, and kidney biopsy. It is important to consult with a nephrologist, a specialist in kidney diseases, for an accurate diagnosis and appropriate management of C3G.