Familial C3 glomerulonephritis associated with mutations in the gene for complement factor B.

We report the first case of familial C3 glomerulonephritis (C3GN) associated with mutations in the gene for complement factor B (CFB). A 12-year-old girl was diagnosed with biopsy-proven C3GN. Her mother had a history of treatment for membranoproliferative glomerulonephritis, and her brother had hypocomplementemia without urinary abnormalities. DNA analysis revealed heterozygosity for CFB p.S367R in the patient, mother and brother. Evaluation of the structure-function relationship supports that this mutation has gain-of-function effects in CFB. The present case suggests that CFB has an important role in the etiology of C3GN and provides a new insight into anticomplement therapy approaches.