C3G and primary IC-MPGN are ultra-rare kidney diseases caused by an overactive C3 protein in the immune system, which mistakenly damages the kidneys. Both conditions are characterised by deposits of C3 protein in the kidneys, with additional deposits of immunoglobulins in the case of primary IC-MPGN.1 The underlying mechanisms behind C3 overactivity vary between individuals, but both conditions can be diagnosed through a kidney biopsy.1
These conditions can affect anyone but are most commonly diagnosed in childhood or early adulthood. They affect males and females equally, and in most cases, there is no clear reason for their development. Factors such as a family history of kidney disease and certain genetic factors may increase the risk.1
Both conditions disrupt the kidneys’ ability to filter blood effectively, leading to symptoms such as proteinuria, swelling (oedema), hypertension (high blood pressure), haematuria (blood in the urine), fatigue, and decreased kidney function.1
C3G and primary IC-MPGN are chronic, progressive diseases that can result in irreversible kidney damage if left untreated. Early diagnosis allows for timely treatment, which can help reduce proteinuria, protect kidney function, and slow disease progression.2
C3G - C3 glomerulopathy
IC-MPGN - immune complex-mediated membranoproliferative glomerulonephritis
References
1. Bomback, A.S., Charu, V., and Fakhouri, F. (2025) Challenges in the Diagnosis and Management of Immune Complex-Mediated Membranoproliferative Glomerulonephritis and Complement 3 Glomerulopathy. Kidney International Reports, 10(1), pp. 17-28.
2. Caravaca-Fontán, F., Toledo-Rojas, R., Huerta, A. et al. (2025). Comparative analysis of proteinuria and longitudinal outcomes in immune complex membranoproliferative glomerulonephritis and C3 glomerulopathy. Kidney International Reports. In press: www.sciencedirect.com/science/article/pii/S246802492500049X