What is DiGeorge Syndrome?

DiGeorge syndrome is characterized by a few specific cardiac malformations, a sub-set of facial attributes, and certain endocrine and immune anomalies.

The cause of DiGeorge syndrome has been identified as a submicroscopic deletion of chromosome 22 in the DiGeorge chromosomal region. It is classified along with velo-cardio-facial syndrome (Shprintzen syndrome) and conotruncal anomaly face syndrome as a 22q11 microdeletion and is sometimes referred to by the simple name 22q11 syndrome.

People with DiGeorge syndrome may have the following congenital heart lesions: tetralogy of Fallot, interrupted aortic arch type B, truncus arteriosus, aberrant left subclavian artery, right infundibular stenosis, or ventricular septal defect. 74% of patients with 22q11 syndrome have conotruncal malformations. 69% of patients are found to have palatal abnormalities including velopharyngeal incompetence (VPI), submucosal cleft palate, and cleft palate.

Some of the facial characteristics of DiGeorge syndrome are bifid uvula, high-arched palate, small mouth and wide set eyes, down-slanting eyes, hooded eyes, long face, malar flatness, cupped low set ears, bulbous nasal tip, and a dimpled or bifurcated nasal tip. Not all people with a 22q11 microdeletion display all, or indeed, any, of these characteristics.

Immune deficiency of varying severity, hypocalcemia (which may lead to seizures) and hypoparathyroidism are some of the most prominent features of DiGeorge, (although not of Shprintzen syndrome which is characterized more by cleft palate and speech difficulties). The thymus gland and parathyroid glands are malformed and dysfunctional or missing altogether in a classic DiGeorge syndrome case.

Learning disorders and developmental delay effect 70% - 90% of individuals with DiGeorge syndrome.

The 22q11 microdeletion can be inherited and is found to be so in about 6% of cases. Parents with the 22q11 microdeletion have a 50% chance of passing the deletion to their offspring. 94% of DiGeorge cases are de novo deletions.

Alcohol consumption during the early stages of fetal development may be one of many environmental explanations for the microdeletion.

Prenatal testing for DiGeorge syndrome is widely available and is recommended for fetuses that have been detected as having cleft palate or heart malformation through ultrasound, and have at least one parent testing positive for the 22q11 microdeletion. Diagnosis at any stage of gestation is helpful in managing DiGeorge syndrome and planning for the care of the neonate.

Infants with the 22q11 microdeletion should be monitored for hypocalcemia, renal function and low lymphocyte count. Babies with low lymphocyte counts should be seen by an immunologist and should not be given live vaccine immunizations.

References

Human Genetics 90:663-5

American Journal of Human Genetics 50:924-33

Journal of Medical Genetics 30:813-7

Genetic Testing 1:99-108