My five-year-old daughter has DiGeorge syndrome. Her T and B lymphocyte counts are normal, but she gets infections all the time -- ear infections, sinus infections, pneumonia. It seems like she is always on antibiotics -- sometimes the strong stuff with shots and IVs. What can I do to strengthen her immune system and avoid so many antibiotics?

Dr. Greene: It boggles my mind. The development of a single fertilized egg into the trillion-fold complexities of a crying newborn baby with absolutely unique fingerprints and toeprints amazes me. In a building project of this magnitude, accomplished in only 9 months, it's a wonder that major things don't go wrong every time.

The DiGeorge anomaly (formerly DiGeorge syndrome or sequence) is the name given when a particular set of things goes wrong during fetal development. Because this condition usually does not run in families, and because some symptoms look like those of fetal alcohol syndrome, alcohol exposure or other environmental insults during pregnancy used to be blamed for some cases. As you can imagine, this mistake made a tough situation even tougher for parents. Today, more than 95 percent of cases can be traced, not to an exposure, but to a specific genetic problem - a microdeletion of a tiny part of chromosome 22q11.2. Other cases have been traced to deletions on chromosome 10p13. Today, when in vitro fertilization is used, the DiGeorge anomaly can usually be diagnosed even before the embryo is implanted!

This tiny genetic change causesthe lower face and middle of the chest to develop abnormally. Children with DiGeorge anomaly sometimes have rather small mouths, rather widely spaced eyes and low-set ears, but the three classic defects of the DiGeorge anomaly are all focused in the area behind the breastbone. These defects include problems with the large blood vessels leaving the heart, problems with the parathyroid glands, and (most importantly) problems with the thymus.

Congenital heart problems (including interrupted aorta, right aortic arch, truncus arteriosus, and others) can be of immediate, even life-threatening, concern for newborns. Surgical correction or stabilization of these is the first priority. Disasters have occurred, though, when only the cardiac problem was diagnosed and the possibility of the DiGeorge anomaly was not considered. A normal blood transfusion can kill a child with the DiGeorge anomaly-- only irradiated, cytomegalovirus (CMV)-negative blood products should be given because of their weakened immune systems.

Seizures are the next concern. The parathyroid glands regulate the amount of calcium in the bloodstream. When they are absent or deficient, calcium can fall to dangerously low levels. This can cause severe seizures or even death, typically in the first or second month of life. If diagnosed, this problem can be prevented with appropriate calcium supplementation and/or the addition of a vitamin D substitute.

If babies survive the heart problems and seizures of the first several months, they begin to display an increased susceptibility to infections such as pneumonia, infectious diarrhea, and severe thrush. This immunodeficiency is the long and difficult battle of the DiGeorge anomaly. It stems from a missing or defective gland that most people haven't even heard of -- the thymus.

Named for its resemblance in shape to a thyme leaf, the thymus is located immediately beneath the breastbone. This organ is relatively huge during the first few years of life (even before the baby is even born). By puberty, it starts to shrink and disappear.