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Understanding Primary Immunodeficiency

There are greater than 350 types of Primary Immunodeficiency (PI).1 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 often recur.

Some of the more common types of PI include selective IgA deficiency, common variable immune deficiency (CVID), X-linked agammaglobulinemia (XLA), and severe combined immune deficiency (SCID).2

What Primary Immunodeficiency Is Not

Primary immunodeficiency should not be confused with autoimmune disorders or secondary immunodeficiency. With an autoimmune disorder (like rheumatoid arthritis or Type 1 diabetes), the immune system gets confused and attacks the body.3

With secondary immunodeficiency, something else causes the immune system to not work right, like another condition or a medical treatment (such as chemotherapy). The most well-known type of secondary immunodeficiency is acquired immune deficiency syndrome (AIDS), which is caused by the human immunodeficiency virus (HIV).2

Primary Immunodeficiency Can't Be
Caught or Spread

Primary immunodeficiency is not contagious.4 It is caused by errors in the genes of the cells that make up the immune system.2

How Many People Have Primary

Primary immunodeficiency diseases were once thought to be rare, but now as a group, they are considered more common.2 As PI awareness with physicians continues to grow and better diagnostic tools are available, more people are getting diagnosed.5

In a 2005 Immune Deficiency Foundation (IDF) patient survey, it was estimated that a quarter million people in the United States have been diagnosed with PI.6,7

Primary Immunodeficiency Symptoms
and Diagnosis

Susceptibility to infections is one of the most common symptoms of PI. However, the symptoms can vary, and they can be mistaken for common infections, since even healthy people without PI can get sick frequently.8

This is one of the reasons it can be difficult to diagnose PI. In fact, according to the 2007 IDF survey, a PI diagnosis can take about 12.4 years from the time symptoms begin.6

Once thought to be a childhood disease, we now know that PI can be diagnosed at any age.2 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.8

Treating Primary Immunodeficiency

If left untreated, PI can lead to reoccurring infections, and in severe cases, can even lead to damage in organs like the lungs or ears.2,8 There are several medical treatments available to help people with PI manage their condition. Talk to your doctor to find the treatment that's best for you. You can learn about a few different types of immunoglobulin treatments in our Shire Treatments section.


  1. Bousfiha A, Jeddane L, Al-Herz W, et al. The 2015 IUIS Phenotypic Classification for Primary Immunodeficiencies. J Clin Immunol. 2015;35(8):727-738.
  2. Blaese RM, Bonilla FA, Stiehm ER, Younger ME, eds. Patient & Family Handbook for Primary Immunodeficiency Diseases. 5th ed. Towson, MD: Immune Deficiency Foundation; 2013.
  3. Autoimmune disorders. Medline Plus Web site. // Accessed August 1, 2018.
  4. Immune Deficiency Foundation. About primary immunodeficiencies. // Accessed August 1, 2018.
  5. Joshi AY, Iyer VN, Hagan JB, St Sauver JL, Boyce TG. Incidence and temporal trends of primary immunodeficiency: a population-based cohort study. Mayo Clin Proc. 2009;84(1):16-22.
  6. Immune Deficiency Foundation. Primary Immunodeficiency Diseases in America: 2007. The Third National Survey of Patients. Prepared by Abt. SRBI, Inc. May 1, 2009.
  7. Boyle JM, Buckley RH. Population prevalence of diagnosed primary immunodeficiency diseases in the United States. J Clin Immunol. 2007;27(5):497-502.
  8. National Institutes of Health. National Institute of Child Health and Human Development. Primary Immunodeficiency: When the Body's Defenses Are Missing. Bethesda, MD: National Institutes of Health; 1999. NIH publication 99-4149.