What is a 22q11.2 deletion?
Except for mature red blood cells, every cell in the body has chromosomes. Each chromosome is made of protein and deoxyribonucleic acid (DNA). DNA contains the specific instructions that make living creatures unique. Human DNA is organized as 23 pairs of chromosomes. One pair, the sex chromosomes, consists of either two X chromosomes (XX), resulting in a girl, or one X and one Y chromosome (XY), resulting in a boy. The other 22 pairs of chromosomes are numbered 1 through 22.
22q11.2 deletion syndrome (also known as DiGeorge syndrome and velo-cardio-facial syndrome) is a disorder caused by the deletion of a small piece of chromosome 22. 22q11.2 identifies the specific chromosomal location where there is a microdeletion.
How do you test for 22q11.2 deletion?
A molecular test called fluorescence in situ hybridization (abbreviated as FISH) is used to detect and locate a specific DNA sequence on a chromosome. It can be used to determine whether there is a 22q11.2 deletion. If the FISH test is negative but there are symptoms of the disease, further chromosomal studies may be needed.
What are the symptoms of 22q11.2 deletion?
Symptoms, including those listed here, may vary from person to person and can be mild or severe:
- Heart defects
- Autoimmune diseases
- Cleft palate
- Developmental issues and learning disabilities
- Facial characteristics
- Feeding problems
- Hearing loss
- Hypoparathyroidism (low parathyroid hormone)
- Prone to infections
- Kidney abnormalities
If my child has 22q11.2 deletion syndrome, what is the risk for my other children or others in our family?
22q11.2 deletion syndrome affects an estimated 1 in 4,000 to 1 per 7,000 births. Most children with a 22q11.2 deletion are the first person in their family to have that problem as a result of a random event during pregnancy. Affected people may pass the syndrome to their children so it’s helpful to test the parents.
When someone with a 22q11.2 deletion has children of their own, there is a 50-50 chance of passing along a copy of chromosome 22 with that deletion with each pregnancy. This also means, of course, that there is an equal chance that the next child will not inherit the deletion.
If health care professionals determine that neither parent has 22q11.2 deletion syndrome, then the risk for others in the family including their other children (siblings of the child with the 22q11.2 deletion) is no greater than anyone else in the world, which is estimated at 1 in 4,000 to 1 in 7,000 births.