DiGeorge syndrome (DGS), also called DiGeorge anomaly or thymic aplasia, is an immune system disorder that occurs when the thymus gland is absent or not fully developed. Patients are born with this disorder.
The thymus gland is responsible for producing white blood cells called T-cells, which help the body fight against disease and infection. When the thymus gland is absent or underdeveloped, not enough T cells are produced. Therefore, patients with DGS syndrome are vulnerable to infections.
This disorder is also associated with other developmental defects, including abnormalities of the heart and large blood vessels around the heart and face. In addition, DGS patients often have underactive parathyroid glands (hypoparathyroidism) and the tube that leads from the mouth to the stomach (esophagus) is typically underdeveloped.
Depending on how underdeveloped the parathyroid gland is, some patients may experience low calcium levels in the blood, which may lead to seizures. This is because the parathyroid gland is responsible for regulating the body's calcium levels.
The condition is caused by a genetic defect. DGS patients are missing a specific chromosome. The chromosomes contain the genetic makeup of an individual. In a minority of cases, the defect is inherited (passed down from parents to their children). In most cases, patients are born without the gene by chance.
Researchers estimate that about one out of 3,000-4,000 individuals are born with DGS worldwide. Men and women are equally affected by DGS.
The disorder is usually diagnosed soon after birth because of the distinct physical defects and heart abnormalities associated with it.
There is currently no cure for DiGeorge syndrome (DGS). Thymus gland and bone marrow transplants have been conducted with varying effectiveness. Patients typically receive supplements with calcium and vitamin D to manage their underactive parathyroid glands.
The prognosis varies among patients. Some patients who have partial DGS may experience spontaneous T-cell improvement and parathyroid function. However, most patients with complete DGS die within the first six months of life. Most deaths are the result of heart defects. Infections caused by severe immune deficiency are the second most common cause of death.
DiGeorge syndrome (DGS) occurs when patients are missing part of chromosome 22. Chromosomes contain an individual's genetic makeup. This particular chromosome contains about 30 genes that are necessary for proper fetal development. When this chromosome is missing, patients are born with the developmental defects characteristic of DGS.
This defect can be inherited, or it may occur by chance. When DGS is inherited, it is passed down as an autosomal dominant trait by the parents. This means that individuals develop the disorder if they inherit one mutated gene from either parent. Parents who have the disease have a 50% chance of passing the disease on to each of their children.
An estimated 90% of DGS cases occur by chance (de novo). It remains unknown exactly why this chromosome is susceptible to deletion from the genetic code. Some studies suggest that there is a correlation between fetal alcohol syndrome and DGS. However, further research is necessary to determine whether or not these two conditions are related.
SIGNS AND SYMPTOMS
DiGeorge syndrome (DGS) is categorized as: 1) complete (absence of thymus gland); 2) partial (severely underdeveloped thymus gland); or 3) transient (mildly underdeveloped thymus gland). Congenital (present at birth) heart disease is common among patients. A minority of patients experience no heart problems.
Common physical defects associated with DGS include increased space between the eyes, upward slant of the eyes, large ears that are lower than normal with a notched ear fold, unusually small jaws, cleft in the lip, high arched palate, nasally speech, conotruncal heart defects, hearing loss, mental retardation, absent or malformed kidney, low levels of calcium in the blood, small head, and psychiatric disorders in adults (like schizophrenia or bipolar disorder).
Infections: Individuals with an absent or underdeveloped thymus gland have a weakened immune system because this gland produces important white blood cells called T-cells. Therefore, patients with DiGeorge syndrome (DGS) are susceptible to infections that may be fatal. Patients may experience chronic runny nose, recurrent pneumonia, oral thrush (yeast infection of the mouth), and diarrhea. Patients are generally weak and may also be susceptible to sudden death.
Seizures: DGS patients typically have underactive parathyroid glands. These glands regulate the calcium levels in the blood. Therefore, DGS patients usually have calcium deficiencies, which may lead to seizures.
General: DiGeorge syndrome (DGS) is usually diagnosed soon after birth because of the distinct physical defects and heart abnormalities that are associated with the disorder. If DGS is suspected, a blood test will indicate abnormalities in the levels of white blood cells. The standard diagnostic tool for DGS is genetic testing called a fluorescent in situ hybridization (FISH) studies. Once DGS is diagnosed, an echocardiogram can be performed to detect abnormalities of the heart. Pregnant women who are concerned that their babies may have a genetic immune disorder may undergo amniocentesis or chorionic villus sampling.
Blood test: A blood test will detect low or nonexistent levels of T-cells and increased levels of B-cells in the blood. In healthy individuals, T-cells make up 68-75% of all the white blood cells, while B-cells make up 10-20% of all the white blood cells.
Echocardiogram: An echocardiogram is used to detect abnormalities in the patient's heart. During the procedure, which is performed at a hospital, three flat, sticky patches, called electrodes, are attached to the patient's chest. These electrodes are attached to an electrocardiograph monitor, which records the electrical activity of the heart. The healthcare provider will then rub a wand called a sound-wave transducer over the patient's chest. This produces images of the heart on the electrocardiograph monitor and the healthcare provider is able to detect abnormalities. This painless and non-invasive procedure generally takes about 40 minutes.
Fluorescent in situ hybridization (FISH) studies: A fluorescent in situ hybridization (FISH) study is used to determine whether the patient is missing chromosome 22. During the procedure, which is performed at a genetic testing laboratory, a sample of the patient's blood is taken. The blood sample is then fluorescently stained. This causes the chromosomes in the blood to glow under ultraviolet light. The scientist is then able to detect chromosomal abnormalities. Patients who are missing all or part of chromosome 22 are diagnosed with DGS.
Prenatal DNA analysis: Pregnant mothers may have their unborn children tested for the disorder. In order to retrieve a sample of the fetus' cells for testing, amniocentesis or chorionic villus sampling may be performed. During amniocentesis, a long, thin needle is inserted into the pregnant woman's abdominal wall to the uterus. A small amount of fluid is removed from the sac surrounding the fetus. During chorionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the placenta. There are risks associated with these procedures, including miscarriage. Patients should discuss the potential risks and benefits of these procedures with their healthcare providers.
General: There is currently no cure for DiGeorge syndrome (DGS). Supplements with calcium and vitamin D are used to manage an underactive parathyroid gland. A bone marrow transplant may help boost the immune system. Early thymus transplantations are controversial because their safety and effectiveness remain unclear.
Bone marrow transplant (BMT): Bone marrow transplants (BMTs) have been conducted with varying results. In studies, some patients experienced a boost in their immune systems after a BMT. However, it is unknown whether these patients had partial DGS. Patients who have partial DGS may experience spontaneous improvements in T-cell functioning.
Calcium supplements: Calcium supplements are typically given to patients who have an underactive parathyroid gland. Calcium gluconate (Kalcinate©) has been administered intravenously (injected into the vein) to prevent seizures associated with low levels of calcium. Alternatively, calcium carbonate (Os-Cal©, Titralac©, Oystercal,© or Caltrate©) has been taken by mouth.
Early thymus transplant: It remains unknown whether an early thymus transplant is safe and beneficial for patients with DGS. During this procedure, the thymus gland of a fetus is surgically transplanted into a young DGS patient. The transplanted thymus tissue is taken from a newborn who received heart surgery. During heart surgery, a small amount of thymus tissue must be removed in order for the surgeon to reach the heart. Instead of discarding the thymus tissue, it can be transplanted into a newborn with DGS. It is recommended that the transplant be conducted before complications of infections develop.
Patients who have partial DGS do not require thymus transplants because their T-cells may spontaneously improve.
Vitamin D supplements: Vitamin D supplements are typically given to patients who have an underactive parathyroid gland. Supplementation with vitamin D helps the body absorb more calcium, which subsequently helps prevent seizures in DGS patients. A liquid solution called ergocalciferol, vitamin D-2 (Drisdol©) has been taken by mouth along with calcium supplements.
Currently, there is insufficient available evidence on the safety and efficacy of integrative therapies for the treatment or prevention of DiGeorge syndrome.
Currently, there is no known method to prevent DiGeorge Syndrome (DGS).
Patients should take precautions to avoid contracting infections associated with the disease, such as thoroughly washing their hands with soap and water. Patients should talk to their healthcare providers about recommended immunizations. Patients should avoid close contact with individuals who have contagious illnesses because they have an increased risk of contracting infections.
Patients who have the disorder may wish to receive genetic counseling. A counselor will provide information and answer questions about the risk of passing the disorder on to the patient's children
This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).
- Hollander G, Gill J, Zuklys S, et al. Cellular and molecular events during early thymus development. Immunol Rev. 2006 Feb;209:28-46. .View abstract
- Immune Deficiency Foundation. www.primaryimmune.org. Accessed May 21, 2007.
- Machado AM, Simon TJ, Nguyen V, et al. Corpus callosum morphology and ventricular size in chromosome 22q11.2 deletion syndrome. Brain Res. 2007 Feb 2;1131(1):197-210. Epub 2006 Dec 13. .View abstract
- National Primary Immunodeficiency Resource Center. www.info4pi.org. Accessed May 21, 2007.
- Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com. Copyright © 2007. Accessed May 21, 2007.
- Wurdak H, Ittner LM, Sommer L. DiGeorge syndrome and pharyngeal apparatus development. Bioessays. 2006 Nov;28(11):1078-86. .View abstract
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