Your immune system helps protect you from infections caused by bacteria and viruses, but sometimes it can mistakenly harm your own body. In immunoglobulin A nephropathy (IgAN), an antibody called immunoglobulin A (IgA) builds up in the kidneys. This buildup can cause inflammation and damage over time.

In this article, we’ll cover what IgAN is, what causes it, and what symptoms to look out for. We’ll also go over how your doctor or nephrologist (a physician specializing in kidney diseases) diagnoses it.

IgAN — or Berger’s disease — affects your kidneys’ small filtering units, known as glomeruli. Your kidneys are responsible for filtering extra water and waste out of your blood. When your kidneys are damaged, they leak protein and blood into your urine.

IgAN is a glomerular disease that can progress over time. Long-term kidney damage can lead to scarring. If it’s left untreated, you may eventually develop end-stage kidney disease.

Each case is different. For some people, this progress can happen quickly. For others, it takes decades.

To better understand what causes IgAN, it helps to first learn about antibodies. Your immune system makes five types of antibodies to protect you from getting sick. These proteins, or immunoglobulins, are found throughout your body to stop bacteria and viruses from taking hold.

IgA antibodies are located in your bloodstream and the tissues that line your mouth, nose, throat, and digestive tract. They help protect you from tiny organisms like bacteria and viruses in the air you breathe and the food you eat.

Doctors and researchers aren’t quite sure what causes IgAN, but they believe it’s an autoimmune disease. This means that your immune system starts attacking your body’s cells and proteins.

If you have IgAN, your body produces IgA antibodies that are low in galactose, a type of sugar. Your immune system thinks these abnormal antibodies are foreign invaders, and it makes other antibodies to attack them.

When antibodies attach to each other, they form clumps called immune complexes. These clumps can get trapped in the glomeruli, the kidney’s tiny filters, causing inflammation and damage. This eventually can lead to IgAN.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, certain risk factors increase your chances of IgAN. People with a family history of IgAN may be more likely to develop it. Inherited gene changes may play a role.

Your age, race, and sex also affect your risk. IgAN tends to first appear in teenagers and adults in their late 30s.

According to Cleveland Clinic, it’s also more common in European and Asian people. Twice as many men as women have it in the U.S. In addition, health conditions, including HIV, liver disease, and celiac disease, are associated with IgAN.

Most people with IgAN don’t experience symptoms until the disease has progressed. It develops slowly over many years, so it can take time for you to notice any changes. Common symptoms of IgAN include:

• Foamy urine — This is a sign of proteinuria (protein in your urine) caused by leaky filtering units in your kidneys.
• Red or dark urine that looks like cola — This indicates hematuria (blood in urine). In some cases, your urine may contain tiny amounts of red blood cells that can’t be seen without a microscope.
• Hypertension (high blood pressure) — Your kidneys can’t filter out water and fluid properly, so your body holds on to it, raising your blood pressure.
• Edema (swelling) — Extra fluid can collect in your hands and feet, making them puffy or swollen.
• Flank pain — You experience pain between your stomach and back where your kidneys are located.

Your doctor will diagnose IgAN using information from your medical and family history, symptoms, physical exam, and tests. They may also check your blood pressure and look for swelling. Tell your doctor about changes in your urine or pain in your sides or back.

Blood and urine tests can show how well your kidneys are working. A blood test measures your estimated glomerular filtration rate (eGFR), or how well your kidneys filter blood. An eGFR above 90 is normal for most adults but decreases with age. A level below 60 for at least three months may indicate chronic kidney disease (CKD).

You’ll likely provide a urine sample to check for blood and protein. Sometimes, blood in urine can only be detected with testing. A dipstick test can measure blood and protein in the sample. Your doctor may ask for one sample or a 24-hour urine collection.

While blood and urine tests can provide information about your kidney function, a kidney biopsy is the only way to confirm an IgAN diagnosis. They’ll use a long, thin needle to remove a piece of kidney tissue to look at under a microscope. A specialist, known as a pathologist, will look for IgA deposits, inflammation, and damage.

If you notice new signs of IgAN, talk to your doctor or a nephrologist. They can run tests and, if needed, help you start treatment to protect your kidney function. Treatment options may include:

• Medications like ACE inhibitors or angiotensin-receptor blockers (ARBs) to lower blood pressure and urinary protein
• Lifestyle changes, like a low-sodium diet
• Statins to lower cholesterol levels
• Diuretics to help your body clear out extra water

If you have a high-risk case of IgAN that doesn’t respond as well to conventional treatments, your doctor may prescribe corticosteroids or immunosuppressants. These options help calm your immune system so that it makes less IgA.

For some people, current treatment plans include newer options like:

• SGLT2 inhibitors to reduce protein in the urine
• Endothelin receptor antagonists (ERAs) to lower pressure in the kidneys
• Complement inhibitors to reduce kidney inflammation through the immune system
• APRIL blockers to lower the amount of harmful IgA in the body

Your doctor will choose medications based on factors such as the amount of protein in your urine, your kidney function, and your risk of disease progression. Regular monitoring and following your treatment plan can help protect your kidneys and lower the risk of complications.

Some people with IgAN eventually develop kidney failure. If this happens, treatment may include dialysis or a kidney transplant.

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