Table 1.

Summary of Molecular Genetic Testing Used in Maple Syrup Urine Disease

MSUD TypeGene 1Proportion of MSUD Attributed to Mutation of This GeneTest MethodVariants Detected 2
MSUD type 1ABCKDHA45%Sequence analysis 3Sequence variants including:
c.1312T>A 4
Targeted analysis for pathogenic variants 5c.1312T>A 4
Deletion/duplication analysis 6Exon and whole-gene deletions 7, 8
MSUD type 1BBCKDHB35%Sequence analysis 3Sequence variants including:
Targeted analysis for pathogenic variants 5c.548G>C
Deletion/duplication analysis 6Exon and whole-gene deletions 9
MSUD type 2DBT20%Sequence analysis 3Sequence variants
Deletion/duplication analysis 6Exon and whole-gene deletions 10

See Molecular Genetics for information on allelic variants.


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.


A BCKDHA founder variant in certain Mennonite populations (see Prevalence)


Variants detected may vary among testing laboratories.


Testing that identifies deletions/duplications not readily detectable by sequence analysis of the coding and flanking intronic regions of genomic DNA; included in the variety of methods that may be used are: quantitative PCR, long-range PCR, multiplex ligation-dependent probe amplification (MLPA), and chromosomal microarray (CMA) that includes this gene/chromosome segment.


No deletions or duplications involving BCKDHB have been reported to cause MSUD type 1B. (Note: By definition, deletion/duplication analysis identifies rearrangements that are not identifiable by sequence analysis of genomic DNA.)


From: Maple Syrup Urine Disease

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