C3 Glomerulopathy (C3G)
C3 glomerulopathy (C3G) is a rare kidney condition caused by abnormal activation of part of the immune system called the complement system.
Overview
C3 glomerulopathy (C3G) is a rare kidney condition caused by abnormal activation of part of the immune system called the complement system. In C3G, a protein called C3 builds up in the kidney's filtering units (glomeruli). Over time, this causes inflammation and damage to the kidneys. C3G includes two main subtypes: C3 glomerulonephritis (C3GN) and dense deposit disease (DDD). Both affect kidney function but may vary in severity.
Causes and Genetics
C3G is caused by dysregulation (overactivity) of the alternative complement pathway, part of the body's immune defence system. This overactivity may be due to genetic changes in complement-related genes or the development of abnormal antibodies that affect complement regulation. Some individuals have identifiable genetic mutations, while others develop the condition without a clear inherited cause.
Symptoms and Features
Symptoms relate to kidney inflammation and may vary in severity.
Characteristic Symptoms and Features
- Blood in the urine (which may be visible or detected on testing)
- Protein in the urine
- Swelling of the legs, ankles or around the eyes
- High blood pressure
Other Associated Symptoms and Features
- Reduced kidney function over time
- Fatigue
- In some cases, progression to chronic kidney disease
Some individuals may experience repeated episodes of kidney inflammation.
Treatment
Regular monitoring of kidney function is essential. In advanced cases, dialysis or kidney transplantation may be required. Care is usually coordinated through specialist kidney (nephrology) centres.
Research and Future Directions
Ongoing research is focused on developing targeted complement inhibitors that specifically block the abnormal pathway activity seen in C3G. Clinical trials are assessing new medications aimed at reducing kidney inflammation and slowing disease progression. Improved understanding of genetic and immune causes is helping to personalise treatment approaches.