Hereditary complete deficiency of the fourth component of complement: effects on the kidney.

Hereditary complete C4 deficiency has until now been detected in 18 patients. A disturbed clearance of immune complexes probably predisposes these individuals to systemic lupus erythematosus and other immune complex diseases. Renal involvement of hereditary complete C4 deficiency is described in seven patients from three families. Three patients of one family suffered from SLE and a severe mesangial and endocapillary proliferative glomerulonephritis which required immunosuppressive treatment. In two patients from a second family a mild focal and segmental mesangioproliferative glomerulonephritis was present which, except for an episode of acute renal failure in one patient, did not cause serious clinical problems. One additional child died without renal involvement. The patient from a third family developed Henoch-Schoenlein purpura, mesangioproliferative glomerulonephritis with segmental scarring and terminal renal failure. Immunofluorescence studies showed deposition of immunoglobulins and complement C3 in the glomeruli. Severity of renal disease is probably determined by activation of the alternative pathway of complement in the kidney.