Which laboratory findings are typical in PSGN?

Which laboratory findings are typical in PSGN?

• A. Elevated C3 and negative anti-DNase B
• B. Low C3 with positive anti-DNase B
• C. Normal C3 with negative anti-DNase B
• D. Low C4 with positive anti-DNase B

Answer: (D)

Post-streptococcal glomerulonephritis arises from immune complexes formed after a streptococcal infection that deposit in the glomeruli and trigger the classical complement pathway. Activation of this pathway consumes components, particularly C4, and to some extent C3, and this pattern is accompanied by serologic evidence of prior Streptococcus infection (such as anti-DNase B antibodies). Choosing the option with low C4 together with positive anti-DNase B fits this scenario: it reflects immune-complex–driven classical pathway activation (low C4) and a recent streptococcal exposure (positive anti-DNase B). Elevated C3, or normal C3 with negative anti-DNase B, would be less characteristic of PSGN, and normal C3 with negative anti-DNase B would not indicate the post-streptococcal process.

Post-streptococcal glomerulonephritis arises from immune complexes formed after a streptococcal infection that deposit in the glomeruli and trigger the classical complement pathway. Activation of this pathway consumes components, particularly C4, and to some extent C3, and this pattern is accompanied by serologic evidence of prior Streptococcus infection (such as anti-DNase B antibodies).

Choosing the option with low C4 together with positive anti-DNase B fits this scenario: it reflects immune-complex–driven classical pathway activation (low C4) and a recent streptococcal exposure (positive anti-DNase B). Elevated C3, or normal C3 with negative anti-DNase B, would be less characteristic of PSGN, and normal C3 with negative anti-DNase B would not indicate the post-streptococcal process.