Diagnosis of DiGeorge syndrome

Fluorescence in situ hybridization

Diagnosis of DiGeorge syndrome can be made by ultrasound examination around the eighteenth week of pregnancy when abnormalities in the development of the heart or the palate can be detected.  Another technique that is used to diagnose the syndrome before birth is called fluorescence in situ hybridization, or FISH. This technique uses DNA probes from the DiGeorge region on chromosome 22.FISH can be performed on cell samples obtained by amniocentesis as early as the fourteenth week of pregnancy. It confirms about 95 percent of cases of DiGeorge syndrome.

If the mother has not had prenatal testing, the diagnosis of DiGeorge syndrome is sometimes suggested by the child's facial features at birth. The child is also born with a defective immune system and an abnormally low level of calcium in the blood. These defects usually become apparent within 48 hours after birth. The infant's heart defects may lead to heart failure, or there may be seizures and other evidence of a low level of calcium in the blood. The doctor may make the diagnosis of DiGeorge syndrome during heart surgery when he or she notice the absence or abnormal location of the thymus gland. The diagnosis can be confirmed by blood tests for calcium, phosphorus, and parathyroid hormone levels and by the sheep call test for immune function.