Disorders
Chromosome 22 Disorders
Despite being the second smallest chromosome in our bodies, chromosome 22 is of great interest. It contains up to 2% of the total DNA in our cells; approximately 855 genes. It was the first of the chromosomes sequenced as part of the Human Genome Project in 1999.
There are many different chromosome disorders associated with chromosome 22. Conditions such as trisomy 22 and monosomy 22 are typically diagnosed prenatally. Trisomy 22 in its complete form is one of the most common causes of miscarriage, second only to trisomy 16. The 22q11.2 deletion syndrome is seen as frequently as 1 in 2000 people. The 22q11.2 region of chromosome 22 is a hotspot for disorders because of areas known as low copy repeats (LCRs) which give rise to deletions, duplications and translocations. Years of dedication by researchers in the field have helped better describe disorders associated with the 22q region such as Emanuel syndrome, Cat-Eye syndrome, Phelan-McDermid syndrome (22q13 deletions), and have helped identify other conditions related to genes on chromosome 22, such as TANGO2 Deficiency Disorder.
Beyond what is listed below, there may be other chromosome 22 disorders that are unique, with little or no information available. Parents can still benefit from connecting with our group. We offer support for all chromosome 22 disorders.
Despite differences in the conditions, our children may share many similarities. Please browse our website to find further information for the following disorders:
22q11.2 Deletion
22q11.2 Deletion Syndrome occurs in approximately 1-2000 to 4000 births. It is caused by a small deleted area on one chromosome 22, at the q11.2 area.
22q11.2 Duplication
Microduplication 22q11.2 is a chromosomal copy number variant (CNV) that is found in about 1 out of every 700-1000 individuals who undergo chromosomal microarray testing, and in 1 in every 1000-2000 controls (“healthy” people who volunteer for research).
22q11.2 Distal Del/Dup
The 22q11.2 distal deletion is seen less commonly than the “typical” 22q11.2 deletion. It typically involves a deleted area of chromosome 22 covering 2.5-3 Mb.
Emanuel Syndrome
Emanuel Syndrome is caused by the presence of an extra derivative chromosome, which is made up of the top part of chromosome 22 and the bottom part of chromosome 11
Cat Eye Syndrome
Cat Eye Syndrome is also known in the literature as Schmid-Fraccaro Syndrome, Partial Tetrasomy 22, or Inv Dup(22)(q11) (Inverted Duplication).
Phelan-McDermid Syndrome
Phelan-McDermid Syndrome (PMS) is a rare disorder typically caused by a deletion (or other structural change) at the very tip of the q arm of chromosome 22 at the 22q13 region, or due to a variation in the SHANK3 gene.
22q13 Duplication
The 22q13 duplication is a rare condition with very few reported cases.
Complete Trisomy 22
Complete trisomy 22 occurs when an extra (third) copy of chromosome 22 is present in every cell of the body, where there should normally only be two copies. Cases of complete (or full) trisomy 22 are very rare.
Mosaic Trisomy 22
Mosaic trisomy 22 is a rare chromosome disorder in which chromosome 22 is present three times, instead of the usual two times, in some cells of the body. The severity of the disorder can depend on the number of cells in which the extra chromosome 22 is present.
22q12 del/dup
Deletions and Duplications of the 22q12 region of chromosome 22 are rare. There are few reports and limited medical information on people who are affected.
Mosaic Monosomy 22
A mosaic form of monosomy means that one chromosome is missing in only some cells. Monosomy 22 / Mosaic Monosomy 22 are very rare events.
TANGO2 Deficiency Disorder
TANGO2 deficiency disorder (TDD) is relatively newly identified, first being described in 2016. TANGO2 is a gene that resides in the 22q11.2 area of chromosome 22.
Schizophrenia in 22q
Researchers suggest that there is an approximately 25% risk for people with 22q11.2 deletion syndrome to develop psychosis/schizophrenia by adulthood.
Der(22)t(8;22) Syndrome
Supernumerary der(22)t(8;22) syndrome is caused by the presence of a derivative chromosome which includes a partial trisomy of part of both chromosome 8 and chromosome 22.
Disorder References
Chromosome 22. National Library of Medicine. Accessed from https://medlineplus.gov/genetics/chromosome/22/
Atli, E. I., Atli, E., Yalcintepe, S., Demir, S., Mail, C., Eker, D., Ozen, Y., & Gurkan, H. (2021). Clinical Features of Aberrations Chromosome 22q: A Pilot Study. Global Medical Genetics, 9(1), 42–50.
Emanuel B. S. (2008). Molecular mechanisms and diagnosis of chromosome 22q11.2 rearrangements. Developmental Disabilities Research Reviews, 14(1), 11–18. https://doi.org/10.1002/ddrr.3
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