Familial incidence of C3 nephritic factor, partial lipodystrophy and membranoproliferative glomerulonephritis.

C3 nephritic factor is an IgG autoantibody that causes complement activation by stabilizing the alternative pathway C3 convertase. It is associated with partial lipodystrophy and membrano-proliferative glomerulonephritis. The occurrence of C3 nephritic factor, partial lipodystrophy and membranoproliferative glomerulonephritis, whether singly or in any combination, is usually sporadic. We describe the coexistence of all three of these conditions in members spanning two generations of a single family. This suggests that the pathogenesis of these conditions may be linked and that genetically determined factors may, in some circumstances, contribute to disease susceptibility.