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What is primary immunodeficiency (PI)?

The more you know about PI, the better prepared you’ll be every step of the way.

PI is an umbrella term used to describe a group of more than 350 disorders that can cause your immune system to not work like it should.

PI is:

  • Usually inherited or caused by problems in genes of cells in the immune system
  • Characterized by infections that are severe, recurrent, and challenging to treat
  • More common than cystic fibrosis, affecting 1 in 1,200 people in the US

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)

“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

PI causes people to have infections that come back frequently or are often hard to treat.

What are the warning signs of PI?

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.

  • 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 in mouth or fungal infection on skin
  • Need for intravenous antibiotics to clear infections
  • Two or more deep-seated infections including septicemia
  • A family history of PI

“My parents had never heard of this disease. They felt they needed more information before making a decision about treatment.”

Kristi B., 49
Virginia Beach, VA

Most PIs are passed to patients via one or both parents.

PI is caused by errors in the genes of the cells that make up the immune system. These diseases were once thought to be rare, but now as a group, they are considered more common than previously thought. Today, the World Health Organization estimates that about 270,000 people or 1 in 1,200 in the United States have been diagnosed with PI. Nearly 100 times more Americans are living with PI than are currently diagnosed. Today, PI is more common than cystic fibrosis.

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

Susceptibility to infections is one of the most common symptoms of PI. However, these symptoms 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.

Once thought to be a childhood disease, we now know that PI can be diagnosed at any age. When testing for PI, doctors will ask about your family history and do a physical exam. They also will order blood tests to check if your blood cells, antibodies, and immune system are working properly. These tests are important for your doctor to confirm a diagnosis of PI and the type of PI you have.

Here are some questions to consider asking your doctor about living with PI:

  • Who will be part of my healthcare team?
  • Who will be my main point of contact?
  • What can I do to help prevent getting infections?
  • Are there any restrictions on my activity level or diet?
  • Is there a specific medical diet or are there nutritional guidelines you would recommend?
  • Can I get all of the recommended vaccinations?
  • Is there a known genetic component for this type of PI?
  • If so, how will I know if other family members need to be tested?
  • What are the long-term health consequences of PI?
  • Is there a PI support group I can join?
  • Do I need to see any other specialists?
  • Who should I call if I get sick?
  • How can I get help with insurance-related inquiries?

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

Bobbie H., 51
Gainesville, TX

Understanding PI

There are more than 350 types of PI. These disorders all have differences, but the big thing they have in common is that they all cause the immune system to not work right, making it harder to fight off infections. These infections can happen anywhere in the body, they can be hard to get rid of, and they often reappear.

A Few Types of PI

Common variable immunodeficiency (CVID)
People with CVID have decreased levels of antibodies (immunoglobulins) in the blood and are therefore more likely to get infections.

X-linked agammaglobulinemia (XLA)
People with XLA—an inherited form of PI—have very few B cells, which are specialized white blood cells that help protect the body against infection.

Immune globulin G (IgG) Subclass Deficiency
IgG is divided into 4 subclasses: IgG1, IgG2, IgG3, and IgG4. People are said to have an IgG subclass deficiency when they lack or have very low levels of 1 or more IgG subclasses, but their total IgG levels are normal.

Hyper-IgM (HIGM) Syndrome
People with HIGM syndrome have an excess of IgM and reduced levels of other immunoglobulins, including IgG and immune globulin A (IgA).

Selective IgA Deficiency
One of the most common types of PI in Caucasians, selective IgA deficiency, often goes undiagnosed in some people because they are never sick enough to be seen by a doctor. Others, however, may develop a variety of challenges that need medical attention.

Severe combined immunodeficiency (SCID)
SCID, a serious form of PI, is a rare syndrome with multiple genetic causes.

Wiskott-Aldrich Syndrome
Wiskott-Aldrich syndrome is a PI disease that affects both the T and B lymphocytes.

DiGeorge Syndrome
DiGeorge syndrome is a PI disease caused by abnormal formation of certain tissues during fetal development. The defect may affect the thymus gland and impair production of T lymphocytes.

Ataxia-telangiectasia (A-T)
A-T is a PI disease that affects a number of organs.

For more information, please refer to the IDF Patient & Family Handbook for Primary Immunodeficiency Diseases (5th ed) by Blaese RM, Bonilla FA, Stiehm ER, Younger ME, eds.

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