Membranous Nephropathy

Overview

Membranous nephropathy (MN) is a condition in which the body’s immune system targets the filtering membranes within the kidneys. These crucial membranes are responsible for removing waste products from the bloodstream.

Each kidney contains thousands of minuscule filtering units called glomeruli, comprising incredibly fine blood vessels with only three layers: endothelial cells forming a single layer on the inner side of the blood vessel, podocytes creating a single layer on the outer side, and a thin glomerular basement membrane (GBM) sandwiched in between these layers.

The glomerular basement membrane acts as a filter. MN can develop suddenly or gradually worsen over an extended period, often remaining undetected in some individuals for many years.

Causes

Most cases of MN are now understood to be caused by an antibody that targets a protein on the podocyte known as the phospholipase A2 receptor (PLA2R). In individuals with MN, the immune system produces antibodies, which are proteins that typically aid in fighting infections. However, in this condition, instead of targeting an infection, these antibodies attack the podocytes. As a result, the podocytes become unable to retain certain proteins in the bloodstream, leading to their leakage into the urine. This form of MN is referred to as primary MN. Less commonly, MN can be caused by other factors (secondary MN), such as autoimmune disorders (where the body attacks its own cells) like lupus, cancer, certain medications, hepatitis B virus, or parasitic diseases like malaria.

Symptoms

Due to damaged podocyte cells, the main symptoms of MN are caused by protein loss in the urine. Nephrotic syndrome is the collective name for MN’s signs and symptoms. Nephrotic syndrome warning signs include:

• Weight gain: Due to the edema, people typically acquire water weight.
• Elevated blood pressure, particularly if renal failure develops concurrently with MN.
• Edema (swelling brought on by fluid retention, typically affecting the legs and feet).
• Blood protein levels that are below typical.
• Proteinuria (foamy-appearing urine brought on by excessive protein levels).
• Elevated cholesterol level.
• Fatigue.

Some individuals with MN may not experience noticeable symptoms. In such cases, doctors may detect signs of MN during a routine health check-up or while conducting tests for other health issues.

Risk factors

A greater risk group for MN includes individuals who are:

• More than 40 years old
• Caucasians. In general, Caucasians are more at risk than people of other races, although MN can affect anyone.
• Having a disease like lupus or cancer that can harm the kidneys.