Table 1.

Genomic Testing Used in 22q11.2 Deletion Syndrome

Deletion 1MethodSensitivity
ProbandAt-risk family members
2.54-Mb heterozygous deletion at 22q11.2
  • ISCN: seq[GRCh37] del(22)(q11.2) chr22:18,912,231-21,465,672del 2
  • ClinGen ID: ISCA-37446
CMA 3100%100%
Targeted deletion analysis 4~95%-100% 5100% 6
1.

See Molecular Genetics for details of the deletion and genes of interest included in the region.

2.

Standardized ISCN annotation and interpretation for genomic variants from the Clinical Genome Resource (ClinGen) project (formerly the International Standards for Cytogenomic Arrays (ISCA) Consortium). Genomic coordinates represent the minimum deletion size associated with the 22q11.2 recurrent deletion as designated by ClinGen. Deletion coordinates may vary slightly based on array design used by the testing laboratory. Note that the size of the deletion as calculated from these genomic positions may differ from the expected deletion size because of the presence of segmental duplications near breakpoints. The phenotype of significantly larger or smaller deletions within this region may be clinically distinct from the 22q11.2 recurrent deletion (see Genetically Related Disorders).

3.

Chromosomal microarray analysis (CMA) using oligonucleotide arrays or SNP arrays. CMA designs in current clinical use target the 22q11.2 region.

4.

Targeted deletion analysis methods can include FISH, quantitative PCR (qPCR), and multiplex ligation-dependent probe amplification (MLPA) as well as other targeted quantitative methods.

5.

The commercially available fluorescence in situ hybridization (FISH) probes, N25 and TUPLE, along with TBX1, are located between low copy number repeat sequences (LCRs) A-B; therefore, the atypical deletions that do not include LCRs A-B are not identifiable using the commercially available FISH probes (Figure 1).

6.

Targeted FISH, MLPA, or other quantitative method analysis may be used to test at-risk relatives of a proband who is known to have the 22q11.2 recurrent deletion.

From: 22q11.2 Deletion Syndrome

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