Membranous nephropathy

Alternative names:

extramembranous glomerulonephritis; glomerulonephritis - membranous; membranous glomerulonephritis; membranous GN

Definition:

A kidney disorder resulting in disruption of kidney function because of inflammation of the glomerulus and changes in the glomerular basement membrane.

Causes, incidence, and risk factors:

The glomeruli are the inner structures of the kidney that include small capillaries surrounded by membranes through which the blood is filtered to form urine. Membranous nephropathy is caused by thickening of the capillary wall of the glomerular basement membrane (the deepest membrane) by immune complexes. The cause is not known.

It is one of the most common causes of nephrotic syndrome, which is the most common presentation of the disease. It may also appear as asymptomatic excretion of protein in the urine. Glomerular filtration rate (the "speed" of blood purification) is usually nearly normal, and examination of sediment in the urine may be unremarkable or may show oval fat bodies, and hyaline, granular, and fatty casts.

Membranous nephropathy may be a primary renal disease of uncertain origin, or it may be associated with other conditions. Risks include systemic disorders such as hepatitis B, malaria, malignant solid tumors, non-Hodgkin's lymphoma, systemic lupus erythematosus, syphilis, and others. Risks also include exposure to substances or medications, including gold, mercury, penicillamine, trimethadione, skin-lightening creams, and others.

The disorder occurs in approximately 2 out of 10,000 people. It may occur at any age but is more common after age 40.