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Bobbi H., 51

Gainesville, TX

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What is primary immunodeficiency (PI)? What are signs of PI?

PI is an umbrella term used to describe a group of more than 450 disorders that have one thing in common: they keep the body’s immune system from working like it should.

People living with PI face unique challenges, because they:

Infection icon. Are more likely to get infections
Time passing icon. Take longer to recover from infections
Calendar icon. Have recurring infections

Facts about PI

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PI is:

  • Usually inherited, which means it runs in families. Some of the disorders can also be caused by genetic and environmental factors
  • Often characterized by increased susceptibility to infections, repeated infections, and infections that are difficult to treat
  • More common than cystic fibrosis, affecting 1 in 1,200 people in the US
Orange X.

PI is not:

  • Contagious or able to be spread to others
  • A secondary problem with the immune system caused by another disease, such as cancer; medications, such as chemotherapy; or infections, such as human immunodeficiency virus (HIV)
  • Always easy to diagnose. In fact, a PI diagnosis can take about 15 years on average from the time symptoms start

“You name it, I got it: sinus infections, respiratory infections and more. I would get a hangnail, and it would turn into an infection.”

Ann P., 56
Indianapolis, IN

What are the symptoms and signs of PI?

PI can be diagnosed at any age. Symptoms and signs of PI usually involve infections that frequently come back or are unusually hard to treat. The warning signs for adults and children can vary.

Warning icon.

10 warning signs of PI for children

If a child has two or more of the following warning signs, talk to a physician about the possible presence of an underlying PI disorder and a possible PI diagnosis.

  • Four or more new ear infections within one year
  • Two or more serious sinus infections within one year
  • Two or more months on antibiotics with little effect
  • Two or more pneumonias within one year
  • Failure of an infant to gain weight or grow normally
  • Recurrent, deep skin or organ abscesses
  • Persistent thrush (fungus growth) in mouth or fungal infection on skin
  • Need for intravenous antibiotics to clear infections
  • Two or more deep-seated infections such as septicemia
  • A family history of PI
Warning icon.

10 warning signs of PI for adults

If you or someone you know has two or more of the following warning signs, talk to a physician about the possible presence of an underlying PI disorder and a possible PI diagnosis.

  • Two or more new ear infections within one year
  • Two or more new sinus infections within one year, in the absence of allergy
  • One bout of pneumonia per year for more than one year
  • Chronic diarrhea with weight loss
  • Recurrent viral infections (colds, herpes, warts, condyloma)
  • Recurrent need for intravenous antibiotics to clear infections
  • Recurrent, deep abscesses of the skin or internal organs
  • Persistent thrush or fungal infection on the skin or elsewhere
  • Infection with normally harmless tuberculosis-like bacteria
  • A family history of PI
How it's diagnosed

“My pulmonologist finally decided to check my IgG levels. But I walked away from that still not understanding what was going on and what I had.”

Katie J., 30
Huntsville, AL

PI is diagnosed in several ways

Once thought to be a childhood disease, we now know that PI can be diagnosed at any age. Often, diagnosis occurs after an individual has experienced health problems, usually related to recurring or ongoing infections, which prompts a doctor to perform a full clinical evaluation.

When testing for PI, doctors will ask about family history and do a physical exam. They will also order blood tests to check if blood cells, antibodies, and the immune system are working properly. These tests are important to confirm a diagnosis and the type of PI.

Family history

In some cases where there is a known family history of PI, a potential diagnosis can be suspected even before a child is born. Laboratory testing is still needed for confirmation, but understanding how PI can be passed down from generation to generation can help with earlier and more accurate diagnosis.

Newborn screening

The US now tests for a type of PI called severe combined immune deficiency (SCID) as part of the standard newborn screening panel. SCID can lead to life-threatening infections. Newborn screenings can make it possible to catch SCID before a serious complication occurs.

Challenges in PI diagnosis

Susceptibility to infections is one of the most common symptoms of PI. However, symptoms and signs of PI can vary and they can be mistaken for common infections, because even healthy people without PI can get sick frequently. This is one of the reasons it can be difficult to diagnose PI.


“When I was finally diagnosed, it was good to know what was wrong with me. On the other hand, I wondered, ‘Why me? How did I get this?’”

Bobbie H., 51
Gainesville, TX

PI is usually inherited from one or both parents

PI, like many physical traits, can be passed along from parents to children. In the same way that a child inherits the genes that determine hair and eye color, PI can be passed on in families.

Most types of PI are inherited in one of two different ways: X-linked recessive inheritance or autosomal recessive. In rare instances, inheritance can also be autosomal dominant.

X-linked recessive inheritance

With X-linked recessive inheritance, the disease is passed on from mothers to sons. Because the mutation occurs in the genes on the X chromosome, males are affected by the disease while females generally do not experience symptoms and are healthy.

Autosomal recessive inheritance

In autosomal recessive inheritance, both mother and father carry the gene for the disorder, although neither have the disorder and are healthy. If the child inherits the abnormal gene from both parents, he or she will be affected by the disorder. If the child inherits only one abnormal gene, the child will carry the gene, but not actually have the disorder. With this type of inheritance, both male and female children are at equal risk.

Autosomal dominant inheritance

In rare situations, having one gene that carries the mutation can cause the disorder. In these cases, an abnormal gene from one parent is passed down and dominates the normal gene inherited from the other parent. A person with an autosomal dominant disorder has a 50% chance of having a child with the disorder.


“Finally, I knew what was wrong with me. I didn’t really know what the treatment entailed yet, but there was a solution!”

Kristi B., 49
Virginia Beach, VA

There are more than 450 types of PI

These disorders all have differences, but the big thing they have in common is that they all cause problems with the immune system, making it harder to fight off infections. Many types of PI result in an inability to make a very important kind of protein called an antibody or immunoglobulin, which helps the body fight off infections from bacteria or viruses. This can cause an increased susceptibility to infection.

Explore some types of PI

For more information, please refer to the IDF Patient & Family Handbook for Primary Immunodeficiency Diseases  (6th ed) by Ballow M, Epland K, Heimall J, Leiding J, Perez E, Riedl M, Younger ME, eds.

Person using a computer.

What’s your plan?

If you or a loved one has been diagnosed with PI, a doctor can help you craft a treatment plan that’s right for you. Explore treatment options here.

Types of Treatment

MyIgSource community member Kristi B. walking.

Kristi B., 49

Virginia Beach, VA

Recently diagnosed?

A new diagnosis can be overwhelming, and you might have a lot of questions about what happens next. Here are some tips to help you manage your PI.

Living with PI

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June 2020


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