Fetal 22q11.2 Microdeletion Syndrome

What is UNITY Aneuploidy^TM Screen for 22q11.2 microdeletion?

UNITY Aneuploidy^TM Screen for 22q11.2 microdeletion is designed to detect a small missing piece, or deletion, on chromosome 22. Any pregnancy can have this chromosome change, regardless of age, ethnicity or family history. The American College of Medical Genetics and Genomics (ACMG) recommends non-invasive prenatal testing (NIPT) for 22q11.2 deletion syndrome (also known as DiGeorge syndrome) for all pregnancies, as it's the most common microdeletion that can be identified prenatally.

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What is 22q11.2 microdeletion?

People with a 22q11.2 microdeletion have a missing part of chromosome 22 that contains several genes, which act as instructions for our body. Many, but not all, people with a 22q11.2 microdeletion will develop symptoms of 22q11.2 deletion syndrome and may have some physical differences such as cleft palate or heart defects. Some pregnancies with 22q11.2 deletion syndrome may have physical birth defects or other differences identified on ultrasound. There may be other health problems and behavioral issues like ADHD, OCD, or autism spectrum disorder.

Every person with 22q11.2 deletion syndrome will have different medical and developmental needs. Individuals often receive medical care from several different specialists. With early intervention, monitoring, and management, many people with 22q11.2 deletion syndrome reach adulthood but can experience ongoing health problems. Genetic testing cannot predict the type and severity of symptoms.

22q11.2 deletion syndrome is caused by a microdeletion, or small missing piece, on chromosome 22. The size of this microdeletion can vary between individuals with 22q11.2 deletion syndrome, but most deletions are too small to be identified on other genetic tests like a karyotype. Approximately 90% of people with 22q11.2 deletion syndrome are the first person in their family to have the condition, whereas about 10% inherited it from a parent, who may not realize they have the condition. Even if a child inherits the 22q11.2 microdeletion from a parent, they could be affected very differently. If someone has 22q11.2 deletion syndrome, there is a 50% chance for each of their children to also have this condition.

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Who should get prenatal screening for 22q11.2 microdeletion?

The American College of Medical Genetics and Genomics (ACMG) recommends non-invasive prenatal testing (NIPT) for 22q11.2 deletion syndrome for all pregnancies, as it's the most common microdeletion that can be identified prenatally. Prenatal screening for 22q11.2 deletion syndrome allows for early diagnosis and intervention, which can improve outcomes for affected individuals.

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What do my UNITY Aneuploidy™ Screen results for 22q11.2 microdeletion mean?

UNITY uses an advanced technology to determine whether your baby’s risk of having a 22q11.2 microdeletion is high or low. Most individuals will receive a “low-risk” NIPT result for 22q11.2 deletion syndrome which significantly reduces the chance your pregnancy is affected, but does not completely eliminate it. Some individuals may receive a “high-risk” NIPT result for 22q11.2 deletion syndrome, which indicates there is a much higher chance of your pregnancy having a 22q11.2 microdeletion. Although UNITY Aneuploidy™  Screen is a highly accurate screening test, diagnostic testing is recommended to determine whether your baby has a 22q11.2 microdeletion. 

Before Birth

Testing during pregnancy can be performed by obtaining a sample of placenta (chorionic villus sampling or CVS) or fluid around your baby (amniocentesis) which both contain DNA that is representative of your baby. A CVS is ideally performed between 10 to 13 weeks pregnancy while an amniocentesis is typically performed between 15 to 24 weeks pregnancy. Both procedures are generally safe, but have a small risk for pregnancy complications, including miscarriage.

After Birth

Infants with a 22q11.2 microdeletion may or may not have physical features of the condition. However, if confirmatory testing during pregnancy is not done, the baby’s pediatrician should be informed of this screening result. The baby can have diagnostic testing performed after birth. Physical exam by a medical geneticist can also be considered.

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References Aneuploidy

Trisomy 21, 18, 13 Incidence

• Snijders, R. J. M., Holzgreve, W., Cuckle, H., & Nicolaides, K. H. (1994). Maternal age-specific risks for trisomies at 9—14 weeks’ gestation. Prenatal Diagnosis, 7, 543–552. https://doi.org/10.1002/pd.1970140706

Sex Chromosome Differences

• Cui, X., Cui, Y., Shi, L., Luan, J., Zhou, X., & Han, J. (2018). A basic understanding of Turner syndrome: Incidence, complications, diagnosis, and treatment. Intractable & Rare Diseases Research, 4, 223–228. https://doi.org/10.5582/irdr.2017.01056
• Tartaglia, N. R., Howell, S., Sutherland, A., Wilson, R., & Wilson, L. (2010). A review of trisomy X (47,XXX). Orphanet Journal of Rare Diseases, 1. https://doi.org/10.1186/1750-1172-5-8 
• Nielsen J, Wohlert M. Chromosome abnormalities found among 34,910 newborn children: results from a 13-year incidence study in Arhus, Denmark. Hum Genet. 1991 May;87(1):81-3. doi: 10.1007/BF01213097. PMID: 2037286. 

22q11.2 microdeletion

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