What is Membranous Nephropathy?
Membranous Nephropathy (MEM-bruh-nus nuh-FROP-uh-thee) or MN is characterized by a thickening of the filtering barrier in the kidney called the glomerular basement membrane.
MN is caused by the build- up of immune complexes within the kidney. Immune Complexes are made when a person’s antibodies attack something they consider foreign to the body (an antigen) like an infection or virus.
antibody + an antigen = an immune complex
These immune complexes are normally eliminated while still in the circulatory system, but in MN they they accumulate in glomerular basement membrane. The inflamed membrane does not work normally and allows large amounts of protein through the barrier and into the urine (proteinuria) causing signs and symptoms known as Nephrotic Syndrome. MN is one of the most common causes of Nephrotic Syndrome.
How is Membranous Nephropathy Diagnosed?
Both the immune complexes and the glomeruli of the kidney where the immune complexes accumulate are extremely small and can only be seen under a microscope. Therefore, a kidney biopsy must be performed in order to diagnose MN.
What are the Symptoms of Membranous Nephropathy?
Some symptoms of MN/NS include:
- Proteinuria– Large amounts of protein ‘spilling’ into the urine
- Edema– Swelling in parts of the body, most noticeable around the eyes, hands, and feet that can become painful
- Low Blood Albumin Levels
- Foam in urine
- High Cholesterol in some cases
- High Blood Pressure in some cases
- Tendency to form blood clots if there are high levels of protein in the urine
Emotional stress related to the above symptoms and side effects of medications used to treat MN can take an emotional toll on patients and caregivers. Social isolation, reduced quality of life, anxiety and depression are commonly described by patients.
Who gets Membranous Nephropathy?
Anyone can have MN, but it’s most common in adults over the age of 40 and it is rare in children and adolescents. Men are affected more often than women and Caucasians are affected more commonly than other races. Though it is known how the kidney damage occurs in MN, why the immune complexes occur is unknown. When there is no known cause the disease is called Primary Membranous Nephropathy.
In some cases, the same type of kidney injury occurs but is caused by another illness and is considered Secondary Membranous Nephropathy. MN can be a secondary disease to Lupus, Hepatitis B and C, and even some cancers. It has also been associated with some drugs including non-steroidal anti-inflammatory drugs.
How is Membranous Nephropathy Treated?
There is no specific treatment for Membranous Nephropathy. Supportive care with the use of diuretics to decrease edema and ACE inhibitors to decrease proteinuria are recommended. Immunosuppressive treatment options including steroids should also be considered, but don’t necessarily have consistent results from patient to patient. Recent studies suggest that B cells could play a key role in the pathogenesis of MN. Drugs that cause a depletion of B cells may be beneficial in treating the root cause and therefore prevent progression of the disease.
One-third of patients with MN obtain complete remission, while up to 40% of patients eventually progress to end-stage renal failure. Drugs that offer more complete response rates with lower adverse side effects are truly needed. The greater the proteinuria, the greater the long-term risk for renal failure.
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