DiGeorge syndrome is a deletion type chromosomal abnormality affecting chromosome 22 (thanks to www.medscape.com for this image).
As a result serious developmental abnormalities develop in the fetus in a number of organ systems. The main features are an underdeveloped or absent thymus gland and parathyroid hormone glands affecting the immune system and calcium level in the blood. There are facial deformities including cleft palate or cleft lip and heart defects or aorta deformities. Strabismus (thanks to www.indianpediatrics.net for this image) and ptosis, which is the drooping of the upper eye lids, is also common.
Signs and symptoms
Facial anomalies include a small mouth, a prominent nose with a large tip and small nostrils and puffiness around the eyes. There are small misshaped ears. The children often have a cleft lip or cleft palate, an underdeveloped or absent thymus gland, an parathyroid disorders (underactive) with resulting low blood calcium levels, and congenital heart defects. These can be a tetralogy of Fallot, ventricular septal defects, vascular rings or an interrupted aortic arch.
Related to DiGeorge syndrome is the velo-cardio-facial syndrome that was later found to be due to the same genetic defect.
Other abnormalities may include hearing loss, a malformed or absent kidney, small head (microcephalus). Often there is mild to moderate mental retardation with an IQ in the 70 to 90 range. In adult life bipolar and schizophrenic disorders are more common in these individuals. Because of the underdeveloped or absent thymus gland there are missing T lymphocytes, which are essential for the immune system to overcome viral illnesses. As a result there are frequent infections.
Fluorescent in situ hybridization (FISH) studies show the (22q11.21) defect on chromosome 22.
A small percentage of children with severe immune deficiencies and severe heart abnormalities will die within the first year of life. The majority of children grow up and with medical help stabilize in adulthood. They will need special education and likely also long-term care because of limitations in mental functioning.
2. Behrman: Nelson Textbook of Pediatrics, 17th ed.- 2004 – Saunders, An Imprint of Elsevier