22q11.2 Duplication – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY

Review
In: GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993.
[updated ].

Excerpt

NOTE: THIS PUBLICATION HAS BEEN RETIRED. THIS ARCHIVAL VERSION IS FOR HISTORICAL REFERENCE ONLY, AND THE INFORMATION MAY BE OUT OF DATE.

Clinical characteristics: 22q11.2 duplication is defined for this GeneReview as the presence of a common 3-Mb or 1.5-Mb proximal tandem duplication. The 22q11.2 duplication phenotype appears to be generally mild and highly variable; findings range from apparently normal to intellectual disability / learning disability, delayed psychomotor development, growth retardation, and/or hypotonia. The high frequency with which the 22q11.2 duplication is found in an apparently normal parent of a proband suggests that many individuals can harbor a duplication of 22q11.2 with no discernible phenotypic effect.

Diagnosis/testing: The phenotype is not sufficiently distinct to be specifically suspected on clinical grounds alone. 22q11.2 duplication is not detectable by routine G-banded karyotyping. Most individuals with 22q11.2 duplication are identified by a chromosomal microarray.

Management: Treatment of manifestations: Educational program tailored to individual needs.

Surveillance: Periodic developmental assessments to assure that educational needs are being met.

Genetic counseling: 22q11.2 duplication may be inherited in an autosomal dominant manner or occur as a de novo condition. Most individuals diagnosed with 22q11.2 duplication have inherited the duplication from a parent. A parent who has the duplication 22q11.2 may have a normal or near-normal phenotype (i.e., no physical findings of the 22q11.2 duplication) even though the genomic alteration appears to be identical in the child and the child has obvious clinical features. Offspring of individuals with the 22q11.2 duplication have a 50% chance of inheriting the duplication. Prenatal testing is technically feasible; however, it is not possible to predict the phenotype from a laboratory finding of 22q11.2 duplication.

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