Immune complex glomerulonephritis in a pregnant woman with congenital C9 deficiency.

A 27-year-old woman developed proteinuria, hypertension, and peripheral edema during the ninth month of her first pregnancy. The clinical and serological features were compatible with a diagnosis of toxemia of pregnancy, except for the presence of hypocomplementemia. The patient had glomerulonephritis characterized by large electron-dense deposits, predominantly in the mesangium. Immunofluorescence studies revealed striking accumulations of Clq and C3, and the presence of small amounts of IgG and IgM in the mesangium. Serum and plasma levels of complement components were normal, except for the C9 component. Family studies demonstrated that the C9 deficiency was inherited.