C3G for clinicians

C3 Glomerulopathy (C3G) describes a group of diseases in which uncontrolled complement activation leads to complement deposition within the glomerulus. It is an ultra-rare condition, with an incidence of ~ 1 per million per year. It typically presents in childhood and young adulthood but can present throughout adulthood. C3G is classified into dense deposit disease (DDD) and C3 glomerulonephritis (C3GN) and overlaps with the term membranoproliferative glomerulonephritis (MPGN).

Clinical features of C3G

Clinical Features include proteinuria, haematuria and nephrotic syndrome. Complement consumption, usually at the level of the C3 convertase results in low C3 levels. Drusen, age-related macular degeneration and acquired partial lipodystrophy have been reported in association with C3G. Familial history has been reported in cases of C3G. In particular, large pedigrees of C3G have been identified with Cypriot ancestry with CFHR5 nephropathy. These patients often have synpharyngic haematuria. Prognosis is often worse in males with CFHR5 nephropathy.

Prognosis of C3G

Patients with C3G have a variable clinical course, though the prognosis is generally poor and there are no effective treatments. Approximately 50% of patients progress to end-stage renal failure within 10 years. Disease recurrence following renal transplantation is common, especially in certain forms of C3G such as DDD.