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 toxins, including gold and mercury
• Use of certain medicines, including penicillamine, trimethadione, and skin-lightening creams
• Infections, including hepatitis B, malaria, syphilis, and endocarditis
• Blood cancers, including non-Hodgkin lymphoma and leukemia
• Melanoma, a type of skin cancer
• Systemic lupus erythematosus, rheumatoid arthritis, Graves' disease, and other autoimmune disorders

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