Table 1.

Summary of Molecular Genetic Testing Used in X-Linked Centronuclear Myopathy

Gene 1Test MethodAllelic Variants Detected 2Variant Detection Frequency by Test Method 3
MalesHeterozygous Females
MTM1Sequence analysis 4 / scanning for pathogenic variants 5Sequence variants60%-98% 6, 753%-98% 8
Deletion/duplication analysis 9(Multi)exon or whole-gene deletion/duplication7%7%
1.
2.

See Molecular Genetics for information on allelic variants.

3.

The ability of the test method used to detect a variant that is present in the indicated gene

4.

Examples of pathogenic variants detected by sequence analysis 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 and scanning of the entire gene for pathogenic variants can have similar variant detection frequencies; however, variant detection frequencies for pathogenic variant scanning may differ considerably among laboratories depending on the specific protocol used.

6.

Lack of amplification by PCRs prior to sequence analysis can suggest a putative deletion of one or more exons or the entire X-linked gene in a male; confirmation may require additional testing by deletion/duplication analysis.

7.

Includes the variant detection frequency using deletion/duplication analysis

8.

Sequence analysis of genomic DNA cannot detect deletion of one or more exons or the entire X-linked gene in a heterozygous female.

9.

Testing that identifies deletions/duplications not readily detectable by sequence analysis of the coding and flanking intronic regions of genomic DNA; a variety of methods including quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), or targeted array GH (gene/segment-specific) may be used. A full array GH analysis that detects deletions/duplications across the genome may also include this gene/segment.

From: X-Linked Centronuclear Myopathy

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