Idiopathic Membranous Nephropathy (IMN) is one of the most frequent adult glomerulonephritis often associated to the clinical picture of nephrotic syndrome. In the IMN the antigens are probably located at the base of podocytes, and the glomerular lesions occur by the local formation of immune complexes, with consequent activation of complement and inflammation triggered by the membrane attack complex C5b-9 . Its evolution is variable. The IMN seems a relatively benign disease. A review of 11 reports of the natural history of the disease demonstrated a 10-year renal survival within the relatively tight band of 70% to 90%. A more current pooled analysis of 32 studies estimated survival between 65% and 75% at 10 years and 60% at 15 years .