Membranous nephropathy (MN) is a major cause of nephrotic syndrome in adults and is defined by subepithelial immune complex deposits along the glomerular basement membrane. While primary (or idiopathic) MN often involves known autoantigens such as PLA2R and THSD7A, secondary MN can be associated with autoimmune diseases, infections (for example, hepatitis B or C), malignancies, and certain medications. Despite these discoveries, the detailed mechanisms underlying both primary and secondary MN remain insufficiently understood.　Recently, advances in liquid chromatography–mass spectrometry (LC-MS) have facilitated more extensive proteomic analyses, enabling the identification of potential novel proteins tied to MN pathogenesis. Such findings may not only enhance our understanding of the disease mechanisms involved in both primary and secondary MN but also guide future diagnostic and therapeutic innovations.