Revisiting immunological and clinical aspects of membranous nephropathy.

Idiopathic or primary membranous nephropathy (IMN) is one of the most frequent causes of nephrotic syndrome in adults and the elderly. It is characterized by a thickening of the wall of the glomerular capillaries due to the presence of immune complex deposits. 85% of membranous nephropathy cases are classified as primary or idiopathic (IMN). The rest are of secondary origin (SMN), caused by autoimmune conditions or malignant tumors as lung cancer, colon and melanomas. It is an organ-specific autoimmune disease in which the complement system plays an important role with the formation of the membrane attack complex (MAC; C5b-9), which produces an alteration of the podocyte structure. The antigen responsible for 70-80% of IMN is a podocyte protein called M-type phospholipase A2 receptor (PLA2R). More recently, another podocyte antigen has been identified, the "Thrombospondin type-1 domain-containing 7A" (THSD7A), which is responsible for 10% of the cases of negative IMN for anti- PLA2R.