Complement C3 Levels in Membranoproliferative and Post-infectious Glomerulonephritides

Objectives − Post infectious glomerulonephritis (PIGN) is the most common type of nephritis in children. Presentation is variable, and most cases initially have low serum complement C3. Membranoproliferative glomerulonephritis (MPGN) is a chronic nephritis less frequently seen in children and is also associated with low serum C3. While management of PIGN is predominantly supportive, MPGN usually requires immunosuppressive therapy. Differentiating PIGN from MPGN at presentation is difficult. Early diagnosis can help inform evaluation and treatment decisions.Materials and Methods − This is a retrospective study of all children 1-21 years of age diagnosed with PIGN and MPGN, treated by nephrologists at Nationwide Children’s Hospital between January 2014 and December 2019. Clinical data, results of kidney function, complement levels, urine testing and biopsy were collected. Children with other types of glomerulonephritis were excluded.Results − Fifty-seven children were included (43 with PIGN and 14 with MPGN). PIGN children were younger at presentation (median age: 7 vs 9.5 years, P=0.0159) and more likely to have a C3 level <40 mg/dl compared to MPGN children (P=0.0031). Most children with PIGN (74.42%) had normal complement levels within 12 weeks after diagnosis compared to 35.71% of children with MPGN. More children with MPGN had evidence of chronic kidney disease as compared to PIGN children, who were more likely to have a full kidney recovery. Conclusions  − Younger children with more significant hypocomplementemia at presentation were more likely to have PIGN than MPGN. We recommend earlier evaluation for MPGN in adolescents with milder degrees of hypocomplementemia (>40 mg/dl).