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Paediatric Laboratory Medicine

22q11.2 Deletion Syndrome

Clinical Significance

22q11DS is one of the most common genetic causes of learning disabilities and mild mental retardation, with an incidence of 1 per 4,000 live births. Individuals with 22q11.2 deletion syndrome (22q11DS), also known as DiGeorge syndrome or Velo-Cardio-Facial syndrome, have a number of physical and cognitive clinical features in common, such as congenital heart defects, learning difficulties and characteristic facial features although not everyone with 22q11DS has all of the features or is affected to the same degree of severity.

Genetics

22q11.2 deletion syndrome is caused by deletion of a small part of chromosome 22 at a location designated 22q11.2. The disorder is an autosomal dominant condition and so an individual is affected with 22q11DS when a deletion is present on one of their two copies of chromosome 22. An individual with a 22q11.2 deletion has a 50% chance of transmitting the chromosome 22 with the deletion to a child. Most patients (~90%) with 22q11DS are new occurrences (deletion is not inherited) while ~10% of individuals with 22q11.2 deletion syndrome have inherited the deletion from a parent.

Approximately 90% of individuals with 22q11DS have a “common” 3 Mb deletion that remove of over 40 genes detectable with chromosome FISH analysis. The remaining patients have smaller deletions that are nested within the 3 Mb common deletion region and a few patients with deletions outside this region. To date no correlation has been found between the size or extent of the deletion and the severity of the clinical phenotype. Molecular testing for 22q11DS involves the determination of the copy number of the genes in the 22q11 region to define the relative start and end point of the deletion (see Figure 1 below).

Test Name

22q11.2 Deletion Syndrome

Alternate Name/ Synonym

  • DiGeorge Syndrome (DGS)
  • Velocardiofacial Syndrome (VCFS)
  • Shprintzen Syndrome

Gene Name

  • 29 genes within the 22q11-13 region

Test Code

22qDS

Division

Molecular Genetics

Method

Deletion/duplication analysis via MLPA

External Proficiency Testing

CAP

Turn Around Time

2 weeks (Prenatal samples), 2-3 weeks (Pregnancy/Urgent samples), 4-6 weeks (Routine)

Disease/Condition

22q11.2 Deletion Syndrome

Specimen Type

Blood; extracted DNA is not accepted for this test.

For details about specimen requirements, please refer to: Specimen Types & Requirements (PDF).

Minimum Specimen Requirements

5-10 mL EDTA or ACD
0.5 mL EDTA (neonate)

Storage/Transportation

Room Temperature

Special Requirements

Special Instructions for Genome Diagnostics Samples

If sample shipment >48 hours, ship on ice.

Approval is not required

CPT Codes

81479

Shipping and Contact Information

The Hospital for Sick Children
Rapid Response Laboratory
170 Elizabeth Street, Room 3642
Toronto, ON
M5G 2G3
Canada
Phone: 416-813-7200
Phone: 1-855-381-3212

Interpretation

Interpretation is provided in report

Information Sheet: 22Q11.2 Deletion Syndrome