Membranous nephropathy is a kidney disorder which involves changes and inflammation of the structures inside the kidney that help filter waste and fluids. The inflammation leads to problems with kidney function.

Membranous nephropathy is caused by thickening of part of the glomerular basement membrane. Glomerular basement membrane is a part of the kidneys that helps filter waste and extra fluid from the blood. The exact reason for this thickening is not known.

It is one of the most common causes of nephrotic syndrome. The condition may be a primary kidney disease of uncertain origin, or it may be associated with other conditions.

The following increase your risk for this condition:

• Exposure to substances or medications, including gold, mercury, penicillamine, trimethadione, and skin-lightening creams
• Hepatitis B
• Malaria
• Non-Hodgkin's lymphoma
• Solid cancerous tumors
• Systemic lupus erythematosus
• Syphilis

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

• Edema (swelling) in any area of the body
• Foamy appearance of urine
• Weight gain
• Poor appetite
• Urination, excessive at night
• High blood pressure

Note: Symptoms vary and in many cases there are no symptoms at all.

A physical exam may show swelling (edema).

A urinalysis may reveal protein in the urine or blood in the urine. Glomerular filtration rate (the "speed" of blood purification) is usually nearly normal.

Serum albumin may be low. Blood lipid levels may increase.

Kidney biopsy confirms the diagnosis of membranous nephropathy.