Membranous glomerulonephritis

Alternative names

Membranous nephropathy; Membranous GN; Extramembranous glomerulonephritis; Glomerulonephritis - membranous

Definition

Membranous nephropathy is 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.

Symptoms

• Edema (swelling) in any area of the body, may be generalized
  
• Foamy appearance of urine
  
• Weight gain (from fluid retention)
  
• Poor appetite
  
• Urination, excessive at night
  
• Blood pressure, high
  

Note: Symptoms vary and no symptoms may be present in many cases.

Signs and tests

An examination may be nonspecific except for edema. A urinalysis may reveal protein in the urine and/or blood in the urine (hematuria). Serum albumin may be low. Blood lipid levels may increase. Kidney biopsy confirms the diagnosis of membranous nephropathy.

Treatment

The goal of treatment is to minimize symptoms and slow the progression of the disease. Symptoms should be treated as appropriate. Medications vary. Often, corticosteroids or immunosuppressive medications may be used to attempt to reduce symptoms and progression of the disorder, with variable results. Medications to treat symptoms may include antihypertensive and diuretic medications. Antibiotics may be needed to control infections.