22q11.2 duplication syndrome is a rare

genetic disorder A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorders ...

caused by a

duplication Duplication, duplicate, and duplicator may refer to: Biology and genetics * Gene duplication, a process which can result in free mutation * Chromosomal duplication, which can cause Bloom and Rett syndrome * Polyploidy, a phenomenon also known ...

of a segment at the end of

chromosome 22 Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 49 million DNA base pairs and representing b ...

Presentation

The most frequent reported symptoms in patients with 22q11.2 duplication syndrome are

intellectual disability Intellectual disability (ID), also known as general learning disability in the United Kingdom and formerly mental retardation, Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010). is a generalized neurodevelopmental disorder characterized by signif ...

/learning disability (97% of patients), delayed psychomotor development (67% of patients), growth retardation (63% of patients) and muscular

hypotonia Hypotonia is a state of low muscle tone (the amount of tension or resistance to stretch in a muscle), often involving reduced muscle strength. Hypotonia is not a specific medical disorder, but a potential manifestation of many different diseases ...

(43% of patients). However, these are common and relatively non-specific indications for

cytogenetic Cytogenetics is essentially a branch of genetics, but is also a part of cell biology/cytology (a subdivision of human anatomy), that is concerned with how the chromosomes relate to cell behaviour, particularly to their behaviour during mitosis an ...

analysis, and the extent to which the duplication of 22q11.2 causes these features is currently unknown. The duplication is frequently inherited from a normal parent, so it is clear that intellectual development can be normal.

Genetics

Duplications of 22q11 vary in size and thereby in gene content. They include the typical common 3-Mb microduplication, 1.5-Mb nested duplication, consistent with

non-allelic homologous recombination Non-allelic homologous recombination (NAHR) is a form of homologous recombination that occurs between two lengths of DNA that have high sequence similarity, but are not alleles. It usually occurs between sequences of DNA that have been previously ...

(NAHR) using distinct low-copy repeats. These microduplications likely represent the predicted reciprocal rearrangements to the microdeletions characterized in the 22q11.2 region. Smaller microduplications may occur within this highly dynamic with frequent rearrangements using alternative low-copy repeats as recombination substrates within and distal to the

DiGeorge syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facial features, frequent i ...

region.

Origin of duplication

The majority of 22q11 duplications are inherited often from a parent with a normal or near-normal

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological pr ...

. This is in sharp distinction to

22q11 deletion syndrome DiGeorge syndrome, also known as 22q11.2 deletion syndrome, is a syndrome caused by a microdeletion on the long arm of chromosome 22 (human), chromosome 22. While the symptoms can vary, they often include congenital heart problems, specific facia ...

where about 90% of cases are caused by mutations that occur '' de novo''.

Diagnosis

Treatment

References

External links

Genetics Home Reference
* {{Chromosomal abnormalities Autosomal duplications Genetic anomalies