Table 1.

Molecular Genetic Testing Used in Smith-Magenis Syndrome

Gene 1MethodProportion of Probands with a Pathogenic Variant 2 Detectable by Method
RAI1 CMA (recommended first) 3~90%-95%
Sequence analysis 45%-10% 5
Gene-targeted deletion/duplication analysis 6Unknown
1.
2.

See Molecular Genetics for information on allelic variants detected in this gene.

3.

A chromosomal microarray (CMA) that includes probe coverage of RAI1 can detect deletions of 17p11.2 (interstitial deletion, complex rearrangements, or derivative chromosomes).

4.

Sequence analysis detects variants that are benign, likely benign, of uncertain significance, likely pathogenic, or pathogenic. Variants may include small intragenic deletions/insertions and missense, nonsense, and splice site variants; typically, exon or whole-gene deletions/duplications are not detected. For issues to consider in interpretation of sequence analysis results, click here.

5.

Sequence analysis (particularly of exon 3, in which all pathogenic variants have been found to date) detects RAI1 pathogenic variants in individuals with SMS when cytogenetic and FISH studies are negative for the 17p11.2 deletion [Vilboux et al 2011, Vieira et al 2012, Dubourg et al 2014, Falco et al 2017].

6.

Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods used may include a range of techniques such as quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and a gene-targeted microarray designed to detect single-exon deletions or duplications. Breakpoints of large deletions and/or deletion of adjacent genes may not be determined.

From: Smith-Magenis Syndrome

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