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“Why is my child sick so often?" As primary care pediatricians, we hear that question a lot, especially from parents with a first child in day care. Of course, chances are good that the child simply has an immature immune system, and the problem of multiple infections will resolve with time.
True primary immune deficiencies are rare. Of the 85 or so that have been well described, the most common is lgA deficiency, which occurs in from 1/500 to 1/1,000 in the population. Other immune disorders, such as severe combined immune deficiency ("Boy in the Bubble" disease), are rarer still.
Parents worry if their child comes down with more infections than they perceive is normal. There is more concern for a child who has one or two episodes of severe or unusual invasive infections or Candida unresponsive to topical therapy in the first few years of life than a toddler with several common infections such as upper respiratory infections (URI's), ear infections or sinusitis.
On average, a normal child < 3 y/o and not in day care will experience in one year:
1. 6-10 colds (URI), about half of them with fever.
2. Up to three ear infections.
3. One or two throat infections.
4. Up to four bouts of diarrhea.
In the 3- to 5-year age group, there are less ear infections and URI's with fever, and a slight increase in sore throats.
In day care, these rates of infection can be 1% to 3 times higher . This may amount to about 8-12
URI's and three to four bouts of diarrhea. Children with several siblings and those exposed to cigarette smoke also may have higher than average rates of common infections.
In children with a normal immune system, it takes time for the immune system to fully develop. It's also important for parents to understand that a search for immune deficiencies is unlikely unless other red flags are present.
Remember, true primary immune deficiency causes children to have infections that come back frequently or are unusually hard to cure.
The Red Flags That Indicate A Need For Further Evaluation Are:
1. A family history of primary immune deficiency
2. 8 or more new ear infections within 1 year
3. 2 or more serious sinus infections within 1 year
4. 2 or more pneumonias within 1 year
5. Failure of an infant to gain weight or grow normally
6. Persistent thrush in mouth or elsewhere on skin, after age 1
7. 2 or more serious or reoccurring infections, such as meningitis, osteomyelitis, cellulitis or sepsis
8. An unusual infection. For example, Burkholderia suggests chronic granulomatous disease. Infection

with several different types of common pathogens in several sites, Chronic draining otitis via ear tubes suggests IgG2 deficiency.
9. Multiple invasive infections. Suspect immune globulin deficiency.
10. Specific infections. Meningococcemia suggests a complement deficiency.
11. Failure to respond to a drug that is usually effective.
12. Need for intravenous antibiotics to clear infections
Further evaluation is necessary in a child with a family history for one of the genetically defined immunodeficiencies, such as Bruton's agammaglobulinemia or x-linked lymphoproliferative disease.
If you find a red flag or if the parents are still worried, the following is a basic immune workup that can be done:
1. Complete blood count with differential. This should include IgG, IgA, IgM, and IgE.
2. Tetanus and pneumococcal antibody titers. (Request non-Prevnar strains if the child is immunized)
3. Complement (CH 50) Screen.
4. Skin Test for T-Cell Function. Use Tuberculin Skin Tests as the negative control and two other antigens as positive controls, such as mumps, tetanus, or Candida. Children with normal T-cell function should respond to at least one of the positive controls with greater than 4 mm of redness and swelling.
5. •HIV antibody test.
An abnormality on any of these tests is an indication for referral to a specialist. If these tests are normal, which will be the case more than 95% of the time, there is no reason to refer.
The Immune Deficiency Foundation's Web site, www.primaryimmune.orq , is a great resource for parents. It gives well-illustrated, simple explanations of the immune system and its various disorders.
Adapted from article from Dr. Christopher J. Harrison, a professor pediatric infectious diseases at the
University of Louisville and Kosair Children's Hospital, Louisville, Ky.