Related Experiment Videos
Homozygous C3 deficiency associated with IgA nephropathy
1Department of Internal Medicine, School of Medicine, Tokai University, Isehara, Japan.
Insights
A patient with zero C3 complement developed IgA nephropathy. This suggests an alternative complement pathway may drive kidney disease without C3.
Area of Science:
- Nephrology
- Immunology
- Complement System
Background:
- Homozygous C3 deficiency is a rare genetic condition.
- The complement system plays a crucial role in innate immunity.
- IgA nephropathy is the most common primary glomerulonephritis.
Observation:
- A 23-year-old male with homozygous C3 deficiency presented with asymptomatic proteinuria and hematuria.
- Renal biopsy revealed IgA nephropathy.
- Complement components C1q, C4, C2, C5, C7, C8, and C9 were detected in glomeruli, but C3 was absent.
Findings:
- Despite the complete absence of C3, deposition of early (C1q, C4, C2) and late (C5, C7, C8, C9) complement components was observed.
- The membrane attack complex (MAC) was present in the glomeruli.
- This indicates complement activation occurred via a C3-independent mechanism.
Implications:
- This case challenges the established understanding of complement activation in IgA nephropathy.
- It suggests the existence of alternative complement pathways that can mediate kidney damage.
- Further research is needed to elucidate these C3-independent mechanisms and their clinical relevance in kidney diseases.
Abstract:
A 23-year-old male patient with homozygous C3 deficiency who developed asymptomatic proteinuria and hematuria was reported. Renal biopsy disclosed typical IgA nephropathy with deposition of early- and late-complement components except for C3 deposition. C9 and membrane attack complex were detected in the glomeruli despite the absence of C3. It was suggested that there might be some unknown complement activation mechanism which does not require C3 component.