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Digeorge Syndrome

In the mid 1960s, an endocrinologist named Angelo DiGeorge, MD, recognized that a particular group of clinical features frequently occurred together, including the following:

hypoparathyroidism (underactive parathyroid gland), which results in hypocalcemia (low blood calcium levels)

hypoplastic (underdeveloped) thymus or absent thymus, which results in problems in the immune system

conotruncal heart defects (i.e., tetralogy of Fallot, interrupted aortic arch, ventricular septal defects, vascular rings)

cleft lip and/or palate

The name of DiGeorge syndrome was applied to this group of features.

In the 1970s, Robert Shprintzen, PhD, a speech pathologist, described a group of patients with similar clinical features including cleft lip and/or palate, conotruncal heart defects, absent or hypoplastic thymus, and some of these patients also had hypocalcemia. Dr. Shprintzen named this group of features velo-cardio-facial syndrome, but the syndrome was also referred to as Shprintzen syndrome.

In the 1980s, the technology was developed to identify an underlying chromosome defect in these syndromes. It was determined that over 90 percent of all patients with features of DiGeorge, Shprintzen, and velo-cardio-facial syndromes had a chromosome deletion in the region of 22q11. In other words, this was the same syndrome, but because several different researchers in different areas of expertise had described it, the syndrome carried multiple names. Many physicians and researchers today use the term 22q11 deletion syndrome because it describes the underlying chromosome problem, or velo-cardio-facial syndrome (VCFS) because it describes the main body systems involved. However, for the purposes of this content, we will call it DiGeorge syndrome.

DiGeorge syndrome, also called 22q11.2 deletion syndrome, is a disorder caused by a defect in chromosome 22. It results in the poor development of several body systems.

Medical problems commonly associated with DiGeorge syndrome include heart defects, poor immune system function, a cleft palate, complications related to low levels of calcium in the blood, and delayed development with behavioral and emotional problems.

The number and severity of symptoms associated with DiGeorge syndrome vary greatly. However, almost everyone with DiGeorge syndrome needs treatment from specialists in a variety of fields.

Before the discovery of the chromosome 22 defect, the disorder was known by several names — DiGeorge syndrome, velocardiofacial syndrome, Shprintzen syndrome, CATCH22 and others. Although the term "22q11.2 deletion syndrome" is frequently used today — and is generally a more accurate description — previous names for the disorder are still used.

DiGeorge syndrome is characterized by neonatal hypocalcemia, which may present as tetany or seizures, due to hypoplasia of the parathyroid glands, and susceptibility to infection due to a deficit of T cells. The immune deficit is caused by hypoplasia or aplasia of the thymus gland. A variety of cardiac malformations are seen in particular affecting the outflow tract. These include tetralogy of Fallot, type B interrupted aortic arch, truncus arteriosus, right aortic arch and aberrant right subclavian artery. In infancy, micrognathia may be present. The ears are typically low set and deficient in the vertical diameter with abnormal folding of the pinna. Telecanthus with short palpebral fissures is seen. Both upward and downward slanting eyes have been described. The philtrum is short and the mouth relatively small. In the older child the features overlap Shprintzen syndrome (velocardiofacial syndrome) with a rather bulbous nose and square nasal tip and hypernasal speech associated with submucous or overt palatal clefting. Cases presenting later tend to have a milder spectrum of cardiac defect with ventricular septal defect being common.

For those individuals who survive infancy and early childhood,

A multidisciplinary team best cares for individuals with 22q11.2DS (chromosome 22q11.2 deletion syndrome; DiGeorge syndrome [DGS]); however, one physician (usually the primary physician) must take the lead and provide a medical home for the patient. The primary physician also must monitor growth and development. A system-by-system approach results in the best outcome.

Management of 22q11.2DS includes the following:

Calcium supplementation: For hypoparathyroidism-associated hypocalcemia; vitamin D supplementation may also be needed

Surgery: Cardiovascular surgery, cleft palate repair, and, for congenital anterior glottic webs, tracheotomy or surgical reconstruction

Immunodeficiency: Therapies include thymus transplantation and adoptive transfer of mature T cells (ATMTC) for individuals with complete DiGeorge syndrome and appropriate prophylaxis measures and monitoring autoimmune complications for incomplete or partial DiGeorge syndrome.

Helpful clinical guideline summaries include those from the Joint Council of Allergy, Asthma and Immunology (Practice parameter for the diagnosis and management of primary immunodeficiency[51] ) and the British Committee for Standards in Haematology ([1] Transfusion guidelines for neonates and older children; [2] amendments and corrections to the transfusion guidelines for neonates and older children[52] ).

Contraception

For patients with chromosome 22q11.2 deletion syndrome, gynecologic evaluation and contraceptive education should be instituted at age 12-18 years and after age 18 years.

the life expectancy for an individual with DiGeorge syndrome is that they can live a normal life span. In the majority of cases, they will need to have constant care and will need to be in treatment for varying medical problems. The burden on the families is huge but there are support groups for caretakers that offer support and help.

How is DiGeorge syndrome diagnosed?

The piece of missing chromosome that causes DiGeorge syndrome is so small that it cannot be seen under a microscope. Instead, a special test called the FISH test (fluorescence in situ hybridisation) will be needed to diagnose the condition.

This test shows whether the region of chromosome 22 is present. If only one copy of chromosome 22 'lights up' with fluorescent DNA dye, rather than both copies, the test is positive for 22q11 deletion.

The FISH test can be carried out to diagnose an unborn baby using a sample of cells from the placenta (chorionic villus sampling) or a sample of fluid surrounding the baby (amniocentesis). It can be carried out using a blood sample in children and adults.

However, this test doesn't pick up every case of DiGeorge syndrome. Some people will need to have more advanced DNA tests and occasionally the diagnosis may be solely made on the characteristic features and symptoms.A

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