[Membranous nephropathy]

Membranous nephropathy (MN) is an autoimmune disease caused by circulating antibodies (ab) directed against an antigen expressed on glomerular epithelial cells (podocytes), which are a main component of the glomerular filtration barrier. This immune complex formation leads to a loss of selectivity of the filtration barrier and loss of large amounts of proteins in the urine. As a consequence, a nephrotic syndrome develops which is the clinical hallmark of MN. In 75% of patients, the pathogenic antibody is directed against the Phospholipase A₂ receptor 1 (PLA₂R1). PLA₂R1-ab are highly specific for patients with MN allowing in specific clinical situations to make the diagnosis of MN without need of a kidney biopsy. In addition, an increase, or the depletion of PLA₂R1-ab is followed by a relapse, or remission of disease, respectively, making them an ideal biomarker for treatment management. Since spontaneous remission of disease is common, immunosuppressive treatment is recommended only for patients with a high risk for progressive loss of kidney function, as well as patients with a low probability to develop remission of disease.