Primary Immunodeficiency (PI)

by National Institute of Health

Most of us are no strangers to infections. Just about everybody has had colds and coughs and infected cuts, the flu or chicken pox. Some people have had first-hand experience with infections that are even more serious - pneumonia and meningitis.

Usually, we expect to recover quickly from an infection. We count on our body's immune defenses (sometimes with the help of antibiotics) to get rid of any germs that cause infection, and to protect us against new germs in the future.

Some people, however, are born with an immune defense system that is faulty. They are missing some or, in the worst cases, almost all of the body's immune defense weapons. Such people are said to have a primary immunodeficiency (PI).

There are over 70 different types of PIs. Each type has somewhat different symptoms, depending on which parts of the immune defense system are deficient. Some deficiencies are deadly, while some are mild. But they all have one thing in common: they may open the door to multiple infections.

Individuals with PI - many of them infants and children - get one infection after another. Ear, sinus, and other infections may not improve with treatment as expected, but keep coming back or occurring with less common but severe infections, such as recurrent pneumonia. Besides being painful, frightening, and frustrating, these constant infections can cause permanent damage to the ears or to the lungs.

In the more severe forms of PI, germs which cause only mild infections in people with healthy immune systems may cause severe or life-threatening infections.

Although infections are the hallmark of PIs, they are not always the only health problem, or even the main one. Some PIs are associated with other immune system disorders, such as anemia, arthritis, or autoimmune diseases. Other PIs involve more than the immune system; some, for instance, are associated with symptoms involving the heart, digestive tract, or the nervous system. Some PIs retard growth and increase the risk of cancer.

Today, thanks to rapid advances in medicine, many PI diseases can be successfully treated or even cured. With proper treatment, most people with PIs are not only surviving once-deadly diseases, they are usually able to lead normal lives. Children usually can go to school, mix with playmates, and take part in sports. Most adults with PI are leading productive lives in their communities.

Successfully combatting PI, however, depends on prompt detection. Physicians, parents, and adult patients alike need to recognize when infections are more than "ordinary," so that treatment can be started in time to prevent permanent damage or life-threatening complications.

This booklet is designed to make PIs easier to recognize, and to cope with, by making them more familiar. It describes how these diseases arise, how they affect health, and how they can be treated. It also reports on promising areas of research, and suggests sources of help for patients and their families. It is not intended as a substitute for professional medical care. You should consult your pediatrician or family physician for specific information on the diagnosis, treatment, and clinical care of patients with PI.

What Is Primary Immunodeficiency?

API disease results whenever one or more essential parts of the immune system is missing or not working properly at birth because of a genetic defect. Since the immune system is tremendously complex, hundreds of things can go wrong during development and sometimes the backup systems cannot compensate for the defects.

A variety of developmental errors in the immune system create different types of PIs. They make people susceptible to different kinds of germs and create different sets of symptoms.

PI diseases were once thought to be rare, mostly because only the more severe forms were recognized. Today physicians realize that PIs are not uncommon. They are sometimes relatively mild, and they can occur in teenagers and adults as often as in infants and children.

Very serious inherited immunodeficiencies become apparent almost as soon as a baby is born. Many more are discovered during the baby's first year of life. Others - usually the milder forms - may not show up until people reach their twenties and thirties. There are even some inherited immune deficiencies that never produce symptoms.

The exact number of persons with PI is not known. It is estimated that each year about 400 children are born in the United States with a serious PI. The number of Americans now living with a primary immunodeficiency is estimated to be between 25,000 and 50,000.

As new laboratory tests become more widely available, more cases of PIs are being recognized. At the same time, new types of PI are being discovered and described.

Currently, the World Health Organization lists over 70 PIs and the numbers are increasing.

Among the rarest forms of immune deficiency is Severe Combined Immune Deficiency (SCID). SCID has been reported in small numbers, while some deficiencies, like DiGeorge Anomaly, are diagnosed more commonly.

At the other extreme, an immune disorder called Selective IgA Deficiency may occur in as many as one in every 300 persons. This figure is an estimate, based on studies of blood from blood donors, since most people with IgA deficiency are healthy and never realize they have this disorder.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.