The invention relates to a method for assessing the prognosis of idiopathic membranous nephropathy in a subject, based on the analysis of PLA2R1 epitope profile. The invention further relates to a method for monitoring the progression of idiopathic membranous nephropathy based on the analysis of the PLA2R1 epitope spreading. The invention highlights that three PLA2R1 domains (Cys R, CTLD1 and CTLD7) are involved in anti-PLA2R1 activity, with two of them (CTLD1 and CTLD7) more closely associated with active idiopathic membranous nephropathy and likely linked by a mechanism of epitope spreading.