DiGeorge
SyndromeDiGeorge syndrome is a deletion type chromosomal abnormality affecting
chromosome 22. 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 lip and heart or aorta deformities. Strabismus
and ptosis (drooping of 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 underactive parathyroid gland 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. Diagnostic tests Fluorescent
in situ hybridization (FISH) studies show the (22q11.21) defect on chromosome
22. Prognosis 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.
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