Primary Immunodeficiency : Diagnosing

by National Institute of Health

(Page 3 of 13)

Some children with PI are infected with germs that a healthy immune system would hold in check. These are known as "opportunistic" infections because the germs take advantage of the opportunity afforded by a weakened immune system. Such an unusual infection may be the tip-off to an immunodeficiency.

For example, Pneumocystis carinii is a microscopic parasite that infects many healthy people without making them sick. But when the immune system is compromised, Pneumocystis can produce a severe form of pneumonia.

Toxoplasma is another widespread parasite that usually produces no disease. In persons with a weakened immune system, it causes toxoplasmosis, which can be a life-threatening infection of the brain that can cause confusion, headaches, fever, paralysis, seizures, and coma.

Besides all the infections, some immunodeficiency diseases produce other immune system problems, including autoimmune disorders. Autoimmune disorders develop when the immune system gets out of control and mistakenly attacks the body's own organs and tissues.

In some autoimmune disorders, the faulty immune system targets a single type of cell or tissue. For example, an immune attack on blood cells can lead to anemia (a debilitating loss of red blood cells). An attack on islet cells of the pancreas can lead to diabetes (a disorder caused by insufficient amounts of insulin, a pancreatic hormone that helps the body convert digested food into energy).

In other situations, the immune system strikes multiple cells and tissues, producing diseases such as rheumatoid arthritis or systemic lupus erythematosus (SLE). Rheumatoid arthritis targets primarily the joints, but it can also damage nerves, lungs, and skin. Lupus strikes skin, muscles, joints, kidneys, and other organs, causing rashes, joint pain, fatigue, and fever, among other things.

Finally, an immunodeficiency can be just one part of a complex syndrome, with a telltale combination of signs and symptoms. For example, children with DiGeorge Anomaly not only have an underdeveloped thymus gland (and a corresponding lack of T cells), they typically have congenital heart disease, malfunctioning, or underdeveloped parathyroid glands, and characteristic facial features. Young boys with Wiskott-Aldrich Syndrome, in addition to being prone to infections, develop bleeding problems and a skin rash.

Diagnosing PI

Sometimes the signs and symptoms of a PI are so severe, or so characteristic, that the diagnosis is obvious. In most cases, it is not clear if a long string of illnesses are just "ordinary" infections, or if they are the result of an immunodeficiency.

Many conditions can produce an immunodeficiency, at least temporarily, and most children who seem to have "too many" infections are not, in fact, suffering from an immunodeficiency. Experts estimate that half of the children who see a doctor for frequent infections are normal. Another 30 percent may have allergies, and 10 percent have some other type of serious disorder. Just 10 percent turn out to have a primary or secondary immunodeficiency.

The Basics

When a pattern of frequent infections suggests an immunodeficiency, the doctor begins by exploring the patient's "history" and the family's history, and then conducts a physical examination.

The patient's history. What infections has the patient had in the past, or has now? Have they been unusually frequent, or severe, or long-lasting? Have they failed to respond to standard treatments? When a child who is immunologically normal develops a string of infections, they are usually mild and short-lived, and between infections the child recovers completely.

What, besides a PI, might explain the high rate of infections? Normal immune responses can be suppressed by many factors, including malnutrition, injuries such as burns, and certain types of drugs (corticosteroids, for instance). Immune responses can also be muted by some diseases, such as leukemia, and some infections, including: infectious mononucleosis (mono), measles, chicken pox, and AIDS. In fact, almost every serious illness impairs the immune responses.

Physical examination: Is the child well-nourished and growing well? A severely immunodeficient child is likely to look sickly and pale. Very often the child is underweight and lags behind in growth and development.

The child may be shy or quiet. An active, robust, healthy-looking child is less likely to have a serious immune deficiency.

The doctor will listen for changes in the lungs and look for rashes, sores, thrush in the mouth, an enlarged spleen or liver, and swollen joints. Some immunodeficient children may lack palpable tonsils or lymph nodes in the neck.

Family history. Have any family members or relatives ever been diagnosed with PI or shown an unusual susceptibility to infections? Have there been any infant deaths from infections? Were only boys affected?

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.