Membranoprolferative glomerulonephritis - mechanisms and treatment.

Membranoproliferative glomerulonephritis (MPGN) is a histologic pattern of glomerular damage with many etiologies. In the past, it was divided into secondary and primary, or idiopathic forms. In turn, the idiopathic forms were labeled MPGN types I, II, and III based on ultrastructural localization of the electron-dense 'deposits'. A recent major change in classification relies on the presence of immunoglobulins and complement to determine etiologies that are more in line with the pathogenesis of the disease. Idiopathic MPGN II, now called dense deposit disease and C3 glomerulonephritis, are now recognized as diseases of the alternate complement pathway. They are caused by a variety of alternate complement pathway defects including genetic forms and those due to autoantibodies that either activate accelerators of the pathway or block inhibitors of the cascade. These patients need to be evaluated in a different fashion and receive different therapy than those patients with MPGN forms associated with immunoglobulin deposition.