The Genetics and Biology of 22q11.2 Deletion Syndrome
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22q11.2 deletion syndrome is caused by a missing piece of genetic code on chromosome 22. This usually happens randomly before conception, though about 7% of cases are inherited. The missing DNA often includes the TBX1 gene, which impacts the development of the heart, face, and neck.
Key Takeaways
- • 22q11.2 is a map coordinate indicating a missing piece of DNA on the long arm of chromosome 22.
- • The deletion is typically caused by a random biological error during DNA copying, resulting in about 30 to 40 missing genes.
- • The TBX1 gene is a critical missing gene that provides instructions for building the heart, face, and neck.
- • About 93% of 22q11.2 deletion cases are random, new events (de novo) and are not inherited from a parent.
- • When the condition is inherited, a parent with the deletion has a 50% chance of passing it to each child.
To understand 22q11.2 deletion syndrome, it helps to think of your or your child’s DNA as a massive, multi-volume set of instruction manuals for building and operating a human body. Every person has two copies of each manual (one from each parent). In 22q11.2DS, a small but vital section of the instructions on one copy is missing.
Decoding the Name “22q11.2”
Medical names can sound like a secret code, but “22q11.2” is simply a “map coordinate” for where the missing information is located [1]:
- 22: This refers to Chromosome 22. Humans have 23 pairs of chromosomes.
- q: This stands for the “long arm” of the chromosome (chromosomes have a short arm and a long arm) [2].
- 11.2: This is the specific “address” or band on that long arm where the deletion is found [1].
How the Deletion Happens
The deletion isn’t caused by anything a person did or didn’t do. Instead, it is a biological “typo” that occurs during the complex process of copying DNA.
The region at 22q11.2 is surrounded by “Low Copy Repeats” (LCRs) [3]. Think of these as identical-looking paragraphs that appear in different parts of the instruction manual. Because these sections look so similar, the body’s cell-copying machinery sometimes gets “confused” and misaligns them [4]. During a process called recombination (where DNA is shuffled), this misalignment causes a section of DNA to be skipped [3][5].
The result is a microdeletion—a piece of the chromosome is gone. In most cases (about 85%), this is a 3 Mb deletion, which means about 3 million “letters” of genetic code are missing [6]. This section typically contains about 30 to 40 different genes [1][2].
The Role of the TBX1 Gene
While many genes are missing, researchers have identified one in particular, called TBX1, as a “master controller” for early development [7].
- A Master Architect: TBX1 tells the body how to build the heart, the parathyroid glands, and the structures of the face and neck [7].
- Haploinsufficiency: Because one copy of TBX1 is missing, the body only has half the “instructions” it needs for these tasks. This “half-strength” instruction is often why individuals with the syndrome may have heart defects or cleft palates [7][8].
Inheritance: De Novo vs. Inherited
- De Novo (New): About 93% of cases are “de novo” [9]. This means the deletion was a random event that occurred only in the egg or sperm cell that created the individual [10]. The parents do not have the deletion themselves.
- Inherited: In about 7% of cases, the deletion is passed down from a parent [9].
- Autosomal Dominant: This means a person only needs one copy of the deletion to have the syndrome [11]. If a parent has the deletion, there is a 50% chance of passing it on to each child [9].
Frequently Asked Questions
What does the name 22q11.2 mean?
Is 22q11.2 deletion syndrome inherited from parents?
What causes the chromosome 22 deletion?
What does the TBX1 gene do?
If I have 22q11.2 deletion syndrome, will my children inherit it?
Questions for Your Doctor
- • Can you explain how the loss of the TBX1 gene specifically relates to the physical features or health issues we are seeing right now?
- • Since most cases are 'de novo', do you recommend that parents still undergo genetic testing to completely rule out an inherited deletion?
- • Does the specific size of the deletion (e.g., 3 Mb vs 1.5 Mb) give us any clues about the severity of the symptoms we should expect?
Questions for You
- • How does viewing this genetic deletion as a missing 'instruction manual page' change the way I think about the diagnosis?
- • Am I carrying any feelings of guilt about how this happened that I need to discuss with a counselor?
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References
- 1
The 22q11.2 deletion syndrome: Genetic mechanisms, clinical manifestations, and therapeutic strategies.
Yang S, Zhuang Y, Xin S, et al.
Clinica chimica acta; international journal of clinical chemistry 2026; (586()):120893 doi:10.1016/j.cca.2026.120893.
PMID: 41690495 - 2
Chromosome 22q11.2 Deletion Syndrome: A Comprehensive Review of Molecular Genetics in the Context of Multidisciplinary Clinical Approach.
Szczawińska-Popłonyk A, Schwartzmann E, Chmara Z, et al.
International journal of molecular sciences 2023; (24(9)) doi:10.3390/ijms24098317.
PMID: 37176024 - 3
Optical mapping in Black genomes: Distinct LCR22 structures and 22q11.2 deletion syndrome mechanisms.
Pastor S, Tran O, Lapointe R, et al.
Genetics in medicine : official journal of the American College of Medical Genetics 2026; (28(1)):101614 doi:10.1016/j.gim.2025.101614.
PMID: 41137608 - 4
An exploratory study of predisposing genetic factors for DiGeorge/velocardiofacial syndrome.
Vergés L, Vidal F, Geán E, et al.
Scientific reports 2017; (7()):40031 doi:10.1038/srep40031.
PMID: 28059126 - 5
Population differences of chromosome 22q11.2 duplication structure predispose differentially to microdeletion and inversion.
Porubsky D, Yoo D, Dishuck PC, et al.
bioRxiv : the preprint server for biology 2025; doi:10.1101/2025.07.04.662981.
PMID: 40631282 - 6
Downregulation of genes outside the deleted region in individuals with 22q11.2 deletion syndrome.
Dantas AG, Santoro ML, Nunes N, et al.
Human genetics 2019; (138(1)):93-103 doi:10.1007/s00439-018-01967-6.
PMID: 30627818 - 7
A novel TBX1 missense mutation in patients with syndromic congenital heart defects.
Jaouadi A, Tabebi M, Abdelhedi F, et al.
Biochemical and biophysical research communications 2018; (499(3)):563-569 doi:10.1016/j.bbrc.2018.03.190.
PMID: 29596833 - 8
Novel heterozygous mutation in TBX1 in an infant with hypocalcemic seizures.
Hasegawa K, Tanaka H, Higuchi Y, et al.
Clinical pediatric endocrinology : case reports and clinical investigations : official journal of the Japanese Society for Pediatric Endocrinology 2018; (27(3)):159-164 doi:10.1297/cpe.27.159.
PMID: 30083032 - 9
What is new with 22q? An update from the 22q and You Center at the Children's Hospital of Philadelphia.
Campbell IM, Sheppard SE, Crowley TB, et al.
American journal of medical genetics. Part A 2018; (176(10)):2058-2069 doi:10.1002/ajmg.a.40637.
PMID: 30380191 - 10
A Novel Non-Allelic Homologous Recombination Event in a Parent with an 11;22 Reciprocal Translocation Leading to 22q11.2 Deletion Syndrome.
Pastor S, Tran O, McGinn DE, et al.
Genes 2022; (13(9)) doi:10.3390/genes13091668.
PMID: 36140835 - 11
Adult Height, 22q11.2 Deletion Extent, and Short Stature in 22q11.2 Deletion Syndrome.
Heung T, Conroy B, Malecki S, et al.
Genes 2022; (13(11)) doi:10.3390/genes13112038.
PMID: 36360275
This page explains the genetics of 22q11.2 deletion syndrome for educational purposes only. A genetic counselor or medical geneticist is the best source for discussing your family's specific genetic testing results and inheritance risks.
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