Serum complement levels before and after the onset of acute post-streptococcal glomerulonephritis. A case report.

Low serum C3, properdin, and C5 levels found in the acute stage of acute post-streptococcal glomerulonephritis (APSGN) indicate the presence of aggressive complement activation. We followed serum complement component levels in a child hospitalized with erysipelas who developed APSGN on the 2nd hospital day. Her initial serum sample, obtained prior to the clinical onset of nephritis, had a low properdin level and normal C3 and C5 levels despite the presence of C3 splitting activity. Two days later she developed gross hematuria and subsequent sera contained low C3, properdin, and C5 levels, as is usual in APSGN. These observations suggest that complement activation, predominantly through the alternative pathway, precedes the clinical onset of APSGN.