Lupus nephritis

Symptoms and causes

Lupus nephritis is a problem that occurs often in people who have systemic lupus erythematosus, also called lupus.

Lupus is a disease in which the body's immune system attacks its own cells and organs, called autoimmune disease. Lupus causes the immune system to make proteins called autoantibodies. These proteins attack tissues and organs in the body, including the kidneys.

Lupus nephritis occurs when lupus autoantibodies affect parts of the kidneys that filter out waste. This causes swelling and irritation of the kidneys, called inflammation. It might lead to blood in the urine, protein in the urine, high blood pressure, kidneys that don't work well or even kidney failure.

Kidney cross section

The kidneys remove waste and extra fluid from the blood through filtering units called nephrons. Each nephron contains a filter, called a glomerulus. Each filter has tiny blood vessels called capillaries. When blood flows into a glomerulus, bits — called molecules — of water, minerals, nutrients, and waste pass through the capillary walls. Large molecules, such as proteins and red blood cells, stay in the blood. The filtered molecules then pass into another part of the nephron called the tubule. The water, nutrients and minerals the body needs are sent back to the bloodstream. The extra water and waste become urine that flows to the bladder and is passed out of the body.

Signs and symptoms of lupus nephritis include:

• Blood in the urine.
• Urine that foams because of too much protein.
• High blood pressure.
• Swelling in the legs, ankles or feet and sometimes in the hands and face.
• High levels of a waste product called creatinine in the blood.

As many as half of adults with systemic lupus get lupus nephritis. Systemic lupus causes the body's immune system to damage the kidneys. Then the kidneys can't filter out waste as they should.

The only known risk factors for lupus nephritis are:

• Being male. Women are more likely to get lupus, but men get lupus nephritis more than women do.
• Race or ethnicity. Black people, Hispanic people and Asian Americans are more likely to have lupus nephritis than are whites.

Lupus nephritis can cause:

• Hypertension.
• Kidney failure.
• A higher risk of getting cancer, especially one that starts in the cells of the immune system, called B-cell lymphoma.
• A higher risk of heart and blood vessel problems.