Definition of Membranous nephropathy

Membranous nephropathy: A frequent type of primary glomerular disease -- a disease affecting the glomerulus, the tiny ball-shaped structure in the kidney composed of capillary blood vessels that is actively involved in the filtration of the blood to form urine. The main sign of the disease is marked proteinuria (protein in the urine).

About 40% of people with membranous nephropathy progress to end-stage renal failure after 10 years. The majority (80%) of cases are primary, meaning the cause is not known. The remaining cases are secondary to conditions such as cancer, infection, and drug side effects.

Membranous nephropathy is a glomerular immune-complex disease. Immune deposits form in the glomerular basement membrane that cause a membrane-like thickening. The constituent immune complexes consist of IgG. Cells called podocytes and their membrane-associated proteins play a pivotal role in the development of the disease by providing antigenic targets for circulating antibodies to form the glomerular immune deposits. Membranous nephropathy is also called membranous glomerulonephritis.

The disease can occur before birth due to transmission of antibodies from the mother to the baby. The antibodies are directed against an antigen in podocytes called neutral endopeptidase (NEP). Mutations that truncate (shorten) the metallomembrane endopeptidase (MME) gene, which encodes NEP, have been found to cause the neonatal form of this disease.