Complement and Renal Disease

Commonly in the work up of nephrotic

syndrome we think serum complements are ordered because they help us narrow down our differential diagnosis. Here is a quick reminder of which conditions cause what. As a quick reminder remember that classical activation involves the binding of C1q to the Fc region of IgG and IgM containing immune complexes. This leads to reduced C3 and C4. Alternative activation, on the other hand, is independent of immune complexes but is triggered by polysaccharide antigens, polymeric IgA, injured cells or endotoxins.

Low C3, Normal C4

• DDD
• Post-streptococcal glomerulonephritis

Low C3 and Low C4

• Lupus nephritis
• Subacute bacterial endocarditis
• MPGN 1 and 2
• Cryoglobulinemic glomerulonephritis ( usually c4 more than c3)
• Atheroembolic renaldisease
• HUS/TTP.

-Adrian