Kidney disease. Coloured transmission electron micrograph (TEM) of a section through the glomerulus of a kidney affected by membranous neuropathy. The function of the glomeruli is to filter waste products from the blood. At the core of the glomerulus is a coil of capillaries (white spaces). Between the capillaries and the cells of the glomerulus is the basement membrane (pink). In various neuropathies this membrane becomes inflamed and characteristically thickened, inhibiting proper filtering. Usually the cause of membranous neuropathy is not known, but some cases may be caused by an autoimmune disease.