In PSGN, complement pattern typical?

In PSGN, complement pattern typical?

• A. High C3
• B. Low C4 with normal C3
• C. Normal C3 and C4
• D. Low C3 with normal C4

Answer: (D)

In post-streptococcal glomerulonephritis, immune complexes activate the alternative complement pathway, which leads to consumption and lower circulating C3. The classical pathway (reflected by C4) is not prominently involved, so C4 stays normal. That combination—low C3 with normal C4—is the typical pattern and helps distinguish PSGN from conditions like lupus nephritis (where both C3 and C4 can be low) or other glomerulonephritides where C3 alone is affected. Remember, C3 levels often recover as the illness resolves, while C4 remains normal.

In post-streptococcal glomerulonephritis, immune complexes activate the alternative complement pathway, which leads to consumption and lower circulating C3. The classical pathway (reflected by C4) is not prominently involved, so C4 stays normal. That combination—low C3 with normal C4—is the typical pattern and helps distinguish PSGN from conditions like lupus nephritis (where both C3 and C4 can be low) or other glomerulonephritides where C3 alone is affected. Remember, C3 levels often recover as the illness resolves, while C4 remains normal.