Primary membranous nephropathy (PMN) or idiopathic membranous nephropathy (IMN)

Primary membranous nephropathy (PMN) is a chronic inflammatory disease of the kidney glomeruli leading to renal impairment.

Indications: Suspicion of primary membranous nephropathy (PMN) or idiopathic membranous nephropathy (IMN).

Diagnosis Diagnosis of PMN is traditionally done by renal biopsy with the detection of immune complexes on the epithelial side of glomerular basement membranes. Serological diagnosis of PMN is faster and less invasive for the patient, where anti-PLA 2-R antibodies can be detected in the serum of 70-75 % of patients are diagnosed with PMN/IMN. The test is performed by indirect immunofluorescens (IIF) using cells carrying the PLA 2-R for detecting antibodies. Antibody titers give an indication of clinical status and treatment effect and can be used to follow status of the patient.

Clinic The disease was described 50 years ago as a disease with granular deposits on the epithelial side of the glomerular basement membrane. These deposits were assumed to be immune complexes that had accumulated on the membrane. An animal model could later prove that the antibodies reacted with antigens on podocytes. The antigen was identified, but it turned out that there was no human counterpart. Many years of research found that the antigen is phospholipase A2 receptors on the surface of the podocytes in in the Bowman's capsule in the kidneys that wrap around the capillaries of the glomerulus. In patients with PMN, immune complexes are formed that are deposited in the basement membranes of glomeruli. The immune complexes induce complement activation with consequent formation of membrane attack complexes that lead to damage to the epithelial cells and eventually to proteinuria. Depending on the degree of membrane effects may PMN classified histologically into four stages. Membranous nephropathy as the primary form to be distinguished from secondary membranous nephropathy, which may be secondary to infection, drug treatment, in collagenosis and other autoimmune diseases as well as in tumors . At this secondary form, the patient is improved with treatment of the underlying disease.