Table 1.

Molecular Genetic Testing Used in Maple Syrup Urine Disease

Gene 1, 2Proportion of MSUD Attributed to Pathogenic Variants in GeneProportion of Pathogenic Variants 3 Identified by Method
Sequence analysis 4Gene-targeted deletion/duplication analysis 5
BCKDHA 45%~92%~8% 6, 7
BCKDHB 35%~93%~7%
DBT 20%~86%~14% 8
Unknown 9, 10NA
1.

Genes are listed in alphabetic order.

2.

See Table A. Genes and Databases for chromosome locus and protein.

3.

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

4.

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

5.

Gene-targeted deletion/duplication analysis detects intragenic deletions or duplications. Methods that may be used 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. Gene-targeted deletion/duplication testing will detect deletions ranging from a single exon to the whole gene; however, breakpoints of large deletions and/or deletion of adjacent genes may not be detected by these methods.

6.
7.
8.
9.

Inactivating variants of BCKDK in humans are associated with BCAA deficiency, autism, epilepsy, and intellectual disability that may respond to dietary treatment [Novarino et al 2012].

10.

Defects of PPM1K may account for a subset of human MSUD but to date no cases have been reported.

From: Maple Syrup Urine Disease

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