Immunoglobulin A (IgA) Nephropathy

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What is IgA nephropathy?

IgA nephropathy is a chronic kidney disease that may progress over a period of 10 to 20 years, and can lead to end-stage renal disease. It is caused by deposits of the protein immunoglobulin A (IgA) inside the glomeruli (filters) within the kidney. These glomeruli normally filter waste and excess water from the blood and send them to the bladder as urine. However, the IgA protein prevents this filtering process. This may lead to the following:

• Blood and protein in the urine

• Swelling in the hands and feet

What causes IgA nephropathy?

The IgA protein is a normal part of the body's immune system. It is not known what causes IgA deposits in the glomeruli; however, in more than 10 percent of affected families, IgA nephropathy is inherited by an autosomal dominant gene. Autosomal dominant inheritance means that the gene is located on one of the autosomes (chromosome pairs 1 through 22). This means that males and females are equally affected, and "dominant" means that only one gene is necessary to have the trait. When a parent has a dominant trait, there is a 50 percent chance that any child he or she has will also inherit the trait.

IgA nephropathy is a very heterogeneous condition, which means that the presentation varies greatly between individuals and families. In fact, some persons who inherit the gene may not have any symptoms, but could pass the gene on to the next generation. Men are affected more often than women.

What are the symptoms of IgA nephropathy?

IgA nephropathy is a silent disease that may go undetected for years, but the onset is usually before the age of 40. The most common symptom is blood in the urine. It takes many years to progress to the stage where it causes detectable complications such as swelling, recurrent upper respiratory infections, or intestinal disease.

How is IgA nephropathy diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for IgA nephropathy may include the following:

• Measurement of blood pressure

• Measurement of blood cholesterol levels

• Measurement of protein levels in the urine

• Measurement of protein levels in the blood

• Kidney biopsy (to identify IgA deposits). A procedure in which tissue samples are removed (with a needle or during surgery) from the kidney for examination under a microscope; to determine if cancer or other abnormal cells are present.

What is the treatment for IgA nephropathy?

Specific treatment for IgA nephropathy will be determined by your physician based on:

• Your age, overall health, and medical history

• Extent of the disease

• Your tolerance for specific medications, procedures, or therapies

• Expectations for the course of the disease

• Your opinion or preference

Treatment may include:

• Diet modification

• Cholesterol reduction

• Medication

• Cessation of smoking

• Exercise and maintenance of normal body weight

• High fluid intake

• Blood pressure control

Treatment focuses on slowing the progression of the disease and preventing complications, such as high blood pressure, which further damages the glomeruli. Two groups of blood pressure medications -- angiotensin-converting enzyme inhibitors (ACE inhibitors) and angiotensin receptor blockers (ARBs) -- help protect kidney function by lowering blood pressure and decreasing the loss of protein in the urine, and are most effective at achieving the treatment goals when taken simultaneously. (Women who are pregnant should not take these medications as they can damage the unborn baby.)

Researchers funded by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) are conducting studies to understand how the IgA deposits are formed and whether dietary supplements such as fish oil or medications such as prednisone can inhibit kidney inflammation and scarring.