Lupus nephritis is a type of kidney disease caused by the autoimmune disease systemic lupus erythematosus (SLE). The immune systems of people with SLE — often simply called lupus — make proteins called autoantibodies that attack their own organs and tissues, including the kidneys. This is referred to as an autoimmune attack. These autoantibodies cause damage to the kidneys by accumulating in the tissue and by directly attacking the kidneys themselves.
Lupus nephritis is separated into six classes, or stages. Doctors use the classes of lupus nephritis to describe how much damage has occurred in a person’s kidneys. This can help a person and their doctor make decisions about treatment and track the progression of the disease.
Doctors usually diagnose classes of lupus nephritis by looking at kidney tissue under a microscope. This requires a kidney biopsy — also known as a renal biopsy — which entails removing a small piece of tissue from the kidney.
A doctor who specializes in analyzing tissue, called a pathologist, will usually assess damage to structures in the kidneys called glomeruli. There are approximately 1 million glomeruli in each kidney. Each consists of a bundle of blood vessels connected to a small tube — called a tubule — that collects fluid. The glomeruli filter waste and excess fluid out of the blood and into the urine. The involvement of glomeruli means lupus nephritis is a type of glomerular disease.
The glomeruli contain cells called mesangial cells, which are damaged by lupus nephritis. A pathologist will look at the damage to diagnose the stage of lupus nephritis.
When glomeruli and mesangial cells become damaged, the kidneys cannot properly remove waste and excess fluid from the blood. This can lead to signs and symptoms of lupus nephritis, including:
A person’s signs and symptoms, along with an analysis of their blood and urine, can help a doctor diagnose their lupus nephritis stage.
There are six classes of lupus nephritis. The classes are defined by the amount of damage to the kidneys and renal function (how well the kidney works). Classes can be written using Arabic numbers (e.g., class 2 or class 3) or Roman numerals (e.g., class II or class III).
The following describes the stages of lupus nephritis and the symptoms associated with each stage.
Class 1 is diagnosed when there’s little or no kidney damage, but some immune activity — called an immune deposit or immune complex — is present. These are complexes of the antibodies made by the immune system. A person with class 1 lupus nephritis will generally have no symptoms.
Class 2 is classified as mild kidney disease. A pathologist may detect some inflammation in the kidney.
In class 3, 50 percent or less of the glomeruli in the kidneys have been affected. A pathologist may detect the presence of lesions in the kidneys. There may also be microscopic amounts of blood or protein in the urine.
A person is diagnosed with class 4 lupus nephritis when more than 50 percent of their glomeruli have been affected. A pathologist may also find larger lesions in the kidney tissue. The signs and symptoms of class 4 lupus nephritis include blood and/or excess protein in the urine, as well as high blood pressure.
In class 5 lupus nephritis, a pathologist may detect an excessive amount of immune complexes in the kidneys. Signs and symptoms of class 5 lupus nephritis include high blood pressure, excess protein and/or blood in the urine, extreme swelling, and active lesions on the kidneys.
Class 6 lupus nephritis occurs when more than 90 percent of the glomeruli in the kidney are damaged. Individuals with class 6 lupus nephritis usually develop end-stage renal disease (ESRD) — also called kidney failure. These people are more likely to require dialysis or a kidney transplant. Symptoms of class 6 lupus nephritis include all of the symptoms associated with lupus nephritis and the added signs and symptoms of ESRD, such as nausea, vomiting, fatigue, chest pain, shortness of breath, cramps, and itching.
There are different treatment regimens for the various classes of lupus nephritis. Ultimately, the goal of treatment is to prevent further damage to the kidneys and treat the symptoms of lupus nephritis. Treatment of lupus nephritis varies for each stage, as follows:
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