Infective endocarditis–associated glomerulonephritis is most often associated with which complement pattern?

• A. Low complement levels
• B. High complement levels
• C. Normal complement
• D. Fluctuating complement levels

Answer: (A)

Infective endocarditis–associated glomerulonephritis happens when circulating immune complexes deposit in the kidneys, triggering activation and consumption of complement via the classical pathway. This use of complement proteins lowers the amount circulating in the blood, so the typical pattern is low complement levels, especially C3 (often with C4 also affected). High or normal complement would not fit this immune complex–mediated process, and levels tend to normalize after the infection is treated.