IgA nephropathy is a condition in which a protein (immunoglobulin A) causes damage to the kidneys.
The outcome is very variable. IgA nephropathy may resolve on its own without any further problems. However, IgA nephropathy may cause an increase in blood pressure. Sometimes, over a period of time, the damage to the kidneys gradually leads to kidney failure.
There is no specific treatment but some medicines have been shown to improve the outcome.
Understanding the kidneys and urine production
The kidneys clear waste materials from the body and maintain a normal balance of fluids and chemicals in the body.
The two kidneys lie to the sides of the upper tummy (abdomen), behind the intestines, and on either side of the spine. The kidneys are higher up in the body than people imagine - from behind they are actually partially protected by the lowest ribs. The kidneys move slightly with a change in body position and with movement of the diaphragm with breathing. The diaphragm is the muscle under your lungs that helps you breathe in.
Each kidney is about the size of a large orange, but bean-shaped.
The word 'renal' is a descriptive medical word, meaning related to the kidney. For example, a renal physician is a doctor who looks after people with kidney (renal) diseases.
A large renal artery takes blood to each kidney. The artery divides into many tiny blood vessels (capillaries) throughout the kidney. In the outer part of the kidneys, tiny blood vessels cluster together to form structures called glomeruli.
Each glomerulus (the singular form of glomeruli) is like a filter. The structure of the glomerulus allows waste products and some water and salts to pass from the blood into a tiny channel called a tubule, while keeping blood cells and protein in the bloodstream. Each glomerulus and tubule is called a nephron. There are about one million nephrons in each kidney.
As the waste products, water and salts pass along the tubule there is a complex adjustment of the content. For example, some water and salts may be absorbed back into the bloodstream, depending on the current level of water and salts in your blood. Tiny blood vessels next to each tubule enable this fine-tuning of the transfer of water and salts between the tubules and the blood.
The liquid that remains at the end of each tubule is called urine. This drains into larger channels (collecting ducts) which drain into the inner part of the kidney (the renal pelvis). From the renal pelvis the urine passes down a tube called the ureter which goes from each kidney to the bladder. Urine is stored in the bladder until it is passed out through another tube, called the urethra, when you go to the toilet. The cleaned (filtered) blood from each kidney collects into a large renal vein which takes the blood back towards the heart. The kidneys, ureters, bladder and urethra are, together, called the urinary tract.
What is IgA nephropathy?
IgA nephropathy is one of a group of conditions called glomerulonephritis. In the outer part of the kidneys, tiny blood vessels cluster together to form structures called glomeruli. These filter the blood to make urine. Glomerulonephritis is the name given to a range of conditions that can affect the glomeruli of the kidney. Glomerulo refers to the glomeruli and nephritis means inflammation of the kidney. But, strictly speaking, there is not always inflammation present in some types of glomerulonephritis. In glomerulonephritis there is damage to the glomeruli. This damage interferes with the function of the glomeruli.
IgA nephropathy is caused by antibodies called IgA being trapped in the kidney and causing damage to the kidney. IgA is short for 'immunoglobulin A'. IgA is a type of antibody our body produces to fight infection. Antibodies are small proteins that circulate in the bloodstream. They are part of the body's defence (immune) system and are sometimes called immunoglobulins. They are made by B lymphocytes (a type of white blood cell).
Nephropathy means an illness that damages the kidney. The IgA gets to the kidneys in the bloodstream and then causes scarring and inflammation in the kidney. The scarring and inflammation are very small and can only be seen with a microscope. The glomeruli are damaged by deposits of IgA. IgA nephropathy does not usually run in families, so you need not worry about passing it on to your children.
What causes IgA nephropathy?
The cause of IgA nephropathy is not completely understood. IgA is produced by glands around the throat and bowel to fight off infection. IgA is normally two antibody molecules stuck together.
In IgA nephropathy, these molecules appear to get joined up in longer chains. As these travel around in the blood and pass through the kidney they get stuck in the filters (glomeruli) in the kidney.
The trapped IgA then cause an inflammatory reaction. It is not known why these IgA chains develop.
How common is IgA nephropathy?
IgA nephropathy is the most common cause of glomerulonephritis. However IgA nephropathy is very uncommon.
IgA nephropathy most often starts between 16 and 35 years of age.
What are the symptoms of IgA nephropathy?
These are variable from person to person. In many cases there are no symptoms, but the damage to the filters (glomeruli) causes some blood to appear in the urine. This blood is often invisible, and only detected on routine medical check-ups. In other cases the blood may be visible, coming in attacks every so often. There may also be an increased amount of protein in your urine.
Sometimes a flu-like illness causes an increase in IgA getting to the kidney. This can cause an increased amount of blood in the urine, which then clears after a few days.
IgA nephropathy is usually painless. Sometimes an acute attack can cause pain over the kidneys and a feeling of sickness (nausea) for a couple of days.
What are the tests for IgA nephropathy?
The first tests include urine tests to check for a urine infection and to measure the protein in your urine. Blood tests will include tests to see how well your kidney is working.
The scarring and inflammation in the kidney can only be seen with a microscope. Therefore, IgA nephropathy is normally only diagnosed after a sample (biopsy test of the kidney) is taken.
Is there any treatment for IgA nephropathy?
There is no specific treatment. It is essential to control your blood pressure. The medicines used for blood pressure control with IgA nephropathy are angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs), eg losartan. Even if you don't have high blood pressure, ACE inhibitors and ARBs can reduce your risk of developing chronic kidney disease.
Steroids can also help to reduce the amount of protein in the urine and reduce your risk of chronic kidney disease.
Medicines (a statin) may be needed to treat high cholesterol. Your cholesterol may increase because of IgA nephropathy.
Other treatments that may help include other medicines to reduce your immune system (for example, azathioprine). Medicines that prevent blood clotting in your blood vessels (warfarin or dipyridamole) have also been used. Removing your tonsils (tonsillectomy) may also help.
If you develop chronic kidney disease, this may become severe (end-stage kidney disease). You will then probably need treatment with dialysis and a kidney transplant. Most people with IgA nephropathy do not develop chronic kidney disease.
What are the complications of IgA nephropathy?
High blood pressure may develop. This damages the kidneys and puts a strain on the heart. It is therefore very important to treat high blood pressure if it develops.
Chronic kidney disease may sometimes occur.
There may be protein leakage from the kidneys. This may be slight and only detectable on urine tests. Occasionally, high levels of protein leakage cause swollen ankles and high levels of cholesterol in the blood. This is called nephrotic syndrome.
What is the outcome (prognosis)?
The outcome is very variable, and you will need to be seen regularly to monitor your blood pressure and kidney function:
- IgA nephropathy may go away on its own.
- IgA nephropathy may continue unchanged for many years. You will then only need regular check-ups with blood tests.
- About 1 in 3 people with IgA nephropathy develop chronic kidney disease. Chronic kidney disease may need treatment with kidney dialysis and a kidney transplant.
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Further reading & references
- Lv J, Xu D, Perkovic V, et al; Corticosteroid therapy in IgA nephropathy. J Am Soc Nephrol. 2012 Jun 23(6):1108-16. doi: 10.1681/ASN.2011111112. Epub 2012 Apr 26.
- Reid S, Cawthon PM, Craig JC, et al; Non-immunosuppressive treatment for IgA nephropathy. Cochrane Database Syst Rev. 2011 Mar 16 (3):CD003962. doi: 10.1002/14651858.CD003962.pub2.
- Cheng J, Zhang X, Tian J, et al; Combination therapy an ACE inhibitor and an angiotensin receptor blocker for IgA nephropathy: a meta-analysis. Int J Clin Pract. 2012 Oct 66(10):917-23. doi: 10.1111/j.1742-1241.2012.02970.x.
- Kamei K, Nakanishi K, Ito S, et al; Long-term results of a randomized controlled trial in childhood IgA nephropathy. Clin J Am Soc Nephrol. 2011 Jun 6(6):1301-7. doi: 10.2215/CJN.08630910. Epub 2011 Apr 14.
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