Immunoglobulin A (IgA) deficiency is the most common primary immunodeficiency in humans. It can increase the risk of allergies, asthma, and autoimmune disease.

Primary immunodeficiencies are conditions where your immune system doesn’t function properly. “Primary” means that they don’t have another underlying cause, such as medication side effects or an underlying disease.

People with IgA deficiency don’t produce enough of a substance called IgA. IgA is a type of immunoglobulin, also called an antibody. Antibodies bind to foreign substances and tell your immune system to attack them.

You have five types of antibodies, including IgA, which plays a particularly important role in defending mucus membranes, such as those in your sinuses and lungs.

Keep reading to learn more about IgA deficiency, including symptoms, causes, and treatment.

Most people with IgA deficiency remain without symptoms their entire life. It’s often identified after blood testing for unrelated reasons.

People with IgA deficiency seem to have an increased risk of some types of health problems due to lower-than-normal levels of IgA immunoglobulin in their bodies. The specific conditions seen in people with IgA deficiency seem to vary significantly.

In particular, it’s been linked to an increased risk of:

In a 2023 review, researchers identified the following as the most common types of autoimmune conditions in people with IgA deficiency:

People with IgA deficiency may also be at a moderately increased risk of some cancers, especially those affecting the GI tract.

IgA deficiency is thought to be caused by genetic factors, and it seems to be more common in people with a family history. A temporary form called secondary IgA deficiency can result as a side effect from many types of drugs, such as cyclosporine and antiepileptics

A diagnosis of IgA deficiency requires less than 7 mg/dL of IgA in the blood of a person over the age of four.

Most cases of IgA deficiency appear sporadically without any known cause. However, research shows that people with a first-degree relative may have a higher risk of developing IgA deficiency than people who don’t have an affected first-degree relative. A first-degree relative can be a:

  • full sibling
  • parent
  • child

IgA deficiency seems to be most common in white people and occurs roughly equally between males and females.

No specific treatments have been developed for IgA deficiency. Treatment generally involves managing specific complications. For example, you might receive antibiotics to treat recurrent bacterial infections like pneumonia.

Typically, people with IgA deficiency seem to have a good outlook. In rare cases, some people receive an immunoglobulin infusion where antibodies are infused through an IV into their blood. Healthcare professionals are cautious about administering this treatment due to the risk of anaphylactic shock.

If medications are the underlying cause, IgA levels typically return to normal once you stop taking the medication.

If you’ve previously been diagnosed with IgA, it’s a good idea to connect with a doctor regularly for monitoring, as you may be at an elevated risk of some health conditions, such as gastrointestinal cancer. A healthcare professional may want to screen for these conditions more frequently than they otherwise would.

It’s especially important to seek medical attention if you experience frequent or severe infections, especially of your sinuses, lungs, or gastrointestinal tract.

If you haven’t previously been diagnosed but suspect you may have an immune system problem, it’s also important to speak with a doctor promptly. They can order blood tests to examine the levels of immunoglobulin in your blood and rule out other conditions.

IgA deficiency is a type of immunodeficiency that develops when your body doesn’t produce enough IgA. Many people go through their whole life without developing symptoms, but some people are at an elevated risk of problems such as recurrent sinus or lung infections, autoimmune conditions, or some cancers.

No particular treatment for IgA deficiency has been developed, and treatment often isn’t needed if you currently aren’t experiencing any health problems. A healthcare professional may still want to monitor you regularly for associated conditions like autoimmune disease or allergies.