C3 complement: deficiency and overactivation are different

Understand the connection

C3 is a central part of the complement system, which helps defend against infection and participates in inflammation. Loss of C3 function and excessive complement activation can have very different effects.

Follow the pathway

Dr. Purser distinguishes C3 deficiency from gain-of-function changes and discusses infections, kidney inflammation, and complement-mediated disease. The word “homozygous” alone does not show whether a finding reduces function, increases activity, or is a common benign variant.

Bring these questions to your visit

Ask for the exact variant classification and whether complement levels, kidney tests, or other findings support the interpretation. A specialist can explain when further testing or a targeted treatment discussion is appropriate.