Minimum volume 250 uL
Transport to laboratory : Ambient (8-24 degrees Celsius)
- Not Detected
- Positive
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C3 nephritic factor is an autoantibody which stabilises the C3 convertase complex (C3bBb), which leads to increased C3 consumption in the serum. Therefore, classically C3 is low and C4 is normal in the presence of this autoantibody.
C3 nephritic factor is detected in approximately 80% of patients with dense deposit disease and 50% with C3 glomerulonephritis (1). The detection of C3 nephritic factor is supportive, but not diagnostic of these conditions. Both dense deposit disease and C3 glomerulonephritis are forms of C3 glomerulopathies, which are characterised by C3 deposition within the glomeruli, seen on renal biopsy due to dysregulation of the complement pathway. These conditions affect both children and adults.
C3 nephritic is also detected in a significant proportion of patients with acquired partial lipodystrophy which is characterised by the loss of subcutaneous fat in the upper half of the body. In one series up to 22% of patients with acquired partial lipodystrophy are also affected by dense deposit disease, which can develop years following the clinical onset of acquired partial lipodystrophy (2).
References:
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Smith RJH, Appel GB, Blom AM, Cook HT, D'Agati VD, Fakhouri F, Fremeaux-Bacchi V, J?zsi M, Kavanagh D, Lambris JD, Noris M, Pickering MC, Remuzzi G, de C?rdoba SR, Sethi S, Van der Vlag J, Zipfel PF, Nester CM. C3 glomerulopathy - understanding a rare complement-driven renal disease. Nat Rev Nephrol. 2019 Mar;15(3):129-143. doi: 10.1038/s41581-018-0107-2. PMID: 30692664; PMCID: PMC6876298.
- Misra A, Peethambaram A, Garg A. Clinical features and metabolic and autoimmune derangements in acquired partial lipodystrophy: report of 35 cases and review of the literature. Medicine (Baltimore). 2004 Jan;83(1):18-34. doi: 10.1097/01.md.0000111061.69212.59. PMID: 14747765.