Table 1.

Genomic Testing Used in Williams Syndrome

Deletion 1MethodSensitivity
ProbandAt-risk family members
1.5- to 1.8-Mb heterozygous deletion at 7q11.23
ISCN: seq[GRCh38] del(7)(q11.23) chr7:73,330,452-74,728,172 2
ISCA-37392		CMA 3100%100%
FISH100%100% 4
1.

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

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 7q11.23 recurrent deletion as designated by ClinGen. Deletion coordinates may vary slightly based on array design used by the testing laboratory. Note: The size of the deletion as calculated from these genomic positions may differ from the expected deletion size due to the presence of segmental duplications near breakpoints. The phenotype of significantly larger or smaller deletions within this region may be clinically distinct from the recurrent 7q11.23 deletion (see Genetically Related Disorders).

3.

Chromosomal microarray analysis (CMA) using oligonucleotide arrays or SNP arrays. CMA designs in current clinical use target the 7q11.23 region.

4.

FISH is not appropriate as a diagnostic method for the relative of an affected individual in whom Williams syndrome was not detected by FISH or by CMA designed to target this region.

From: Williams Syndrome

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