In IgA nephropathy, a protein called immunoglobulin A (IgA) gets trapped in the tiny filters (glomeruli) in the kidneys. This causes the kidneys to leak blood and protein into the urine.

IgA refers to the protein. Nephropathy means kidney disease.

Read more about how the kidney works and IgA nephropathy

Inside each kidney, there are about one million nephrons. Each nephron is made up of a glomerulus (when we talk about more than one glomerulus, we say glomeruli), and a renal tubule.

  • Each glomerulus acts like a sieve, helping to remove extra water and waste from the body, and holding on to blood cells and protein, which the body needs.
  • Blood flows into the kidneys and to each glomerulus.
  • Most of the water and some other substances in the blood pass through the glomeruli.
  • This liquid flows into the renal tubule. Most of this liquid moves back into the bloodstream. The rest of it becomes urine.
  • The urine leaves the kidney by the ureters and goes into the bladder, where it is stored until we are ready to go to the toilet.

More about what the kidney does

What happens in IgA nephropathy

A protein called immunoglobulin A (IgA) gets trapped in the glomeruli. This causes the glomeruli to become inflamed (swollen) or damaged. The damaged glomeruli can let blood cells and protein through, which mean they go into the urine.

When a tiny sample of kidney is taken in a kidney biopsy, it can be examined under special microscopes. Dyes can be added to show up specific proteins. The above is an image of a glomerulus – the green represents areas where there are IgA.

After infection

Many children with IgA nephropathy first get symptoms with an infection – this is not in the kidney, but usually in the throat, tonsils, lungs or gut. Most children recover from these infections. But, in a few children the infection seems to trigger IgA nephropathy.

The immune system

Many germs – including bacteria and viruses – can make us sick if they get into the body. The immune system can kill these germs. However, if the immune system is not working properly, it can start to cause problems.

Read more about the immune system


The immune system protects the body against germs such as bacteria and viruses that can cause illness. These germs can enter the body in lots of ways, such as by the nose and throat or the urinary system. If we get a cold or flu, this means that a virus germ has got into the body and started to infect some of our body’s cells.

Germs have special ‘markers’ that are different from the markers on our own body’s cells. This means that the immune system can recognise that they are germs and kill them. We often feel sick for a few days or a few weeks while this is happening.

Parts of the immune system

The immune system has many different ways to protect the body against disease. Some of the parts include those listed below.

  • White blood cells are living cells in the blood. Often, the number of white blood cells found in a blood test can give information about someone’s immune system. The two main types of white blood cells in the immune system are neutrophils and lymphocytes.
  • Antibodies or immunoglobulins recognise the germs that have come into the body, and can bind (stick) to them. There are five types: immunoglobulin A (IgA), immunoglobulin D (IgD), immunoglobulin E (IgE), immunoglobulin G (IgG) and immunoglobulin M (IgM).
  • The complement system is made up of other proteins that float in the blood. These proteins work with (complement) other parts of the immune system to help kill germs or cells infected by germs. Normally, the body controls when complement is activated, so it does not attack the body itself.

When the immune system does not work properly

Sometimes the immune system does not work as expected and can cause problems. For example, sometimes the immune system cannot recognise the body’s own cells and may attack them as if they were invaders like germs.

Will it affect other family members?

Doctors do not think that IgA nephropathy runs in families. If one of your children has this type of glomerulonephritis, it is unlikely that another of your children or another family member will get it.