6-80106772-CCTGGCGCGGGG-CCTGGCGCGGGGCTGGCGCGGGG

Position:

• chr6-80106772-CCTGGCGCGGGG-CCTGGCGCGGGGCTGGCGCGGGG

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_183050.4(BCKDHB):​c.93_103dupGGCGCGGGGCT​(p.Phe35fs) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000766 in 1,436,956 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Likely pathogenic (★★). Variant results in nonsense mediated mRNA decay.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000077 (0 hom.)
• Consequence: BCKDHB NM_183050.4 frameshift
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:9
• Conservation: PhyloP100: 1.02

Genes affected

BCKDHB (HGNC:987): (branched chain keto acid dehydrogenase E1 subunit beta) This gene encodes the E1 beta subunit of branched-chain keto acid dehydrogenase, which is a multienzyme complex associated with the inner membrane of mitochondria. This enzyme complex functions in the catabolism of branched-chain amino acids. Mutations in this gene have been associated with maple syrup urine disease (MSUD), type 1B, a disease characterized by a maple syrup odor to the urine in addition to mental and physical retardation and feeding problems. Alternative splicing at this locus results in multiple transcript variants. [provided by RefSeq, Jan 2016]

BCKDHB (HGNC:):

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 6-80106772-C-CCTGGCGCGGGG is Pathogenic according to our data. Variant chr6-80106772-C-CCTGGCGCGGGG is described in ClinVar as [Likely_pathogenic]. Clinvar id is 189101.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
BCKDHB	NM_183050.4	c.93_103dupGGCGCGGGGCT	p.Phe35fs	frameshift_variant	1/10	ENST00000320393.9	NP_898871.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
BCKDHB	ENST00000320393.9	c.93_103dupGGCGCGGGGCT	p.Phe35fs	frameshift_variant	1/10	1	NM_183050.4	ENSP00000318351.5
BCKDHB	ENST00000356489.9	c.93_103dupGGCGCGGGGCT	p.Phe35fs	frameshift_variant	1/11	1		ENSP00000348880.5
BCKDHB	ENST00000369760.8	c.93_103dupGGCGCGGGGCT	p.Phe35fs	frameshift_variant	1/6	3		ENSP00000358775.4

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000766 AC: 11 AN: 1436956 Hom.: 0 Cov.: 32 AF XY: 0.00000842 AC XY: 6 AN XY: 712878

Gnomad4 AFR exome AF: 0.0000304

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.0000262

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00000817

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:9

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Maple syrup urine disease Pathogenic:5

Likely pathogenic, criteria provided, single submitter	clinical testing	Genome-Nilou Lab	Nov 07, 2021	- -
Pathogenic, criteria provided, single submitter	clinical testing	Revvity Omics, Revvity	May 01, 2021	- -
Likely pathogenic, criteria provided, single submitter	literature only	Counsyl	Dec 23, 2014	- -
Pathogenic, criteria provided, single submitter	clinical testing	Baylor Genetics	Jun 01, 2023	- -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jan 29, 2024	This sequence change creates a premature translational stop signal (p.Phe35Trpfs*41) in the BCKDHB gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in BCKDHB are known to be pathogenic (PMID: 16786533, 22593002). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with maple syrup urine disease (PMID: 16786533, 29307017). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. This variant is also known as c.92_102dup11. ClinVar contains an entry for this variant (Variation ID: 189101). For these reasons, this variant has been classified as Pathogenic. -

Maple syrup urine disease type 1B Pathogenic:3

Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Nov 09, 2020	- -
Pathogenic, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	May 31, 2024	- -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Jul 27, 2020	Variant summary: BCKDHB c.93_103dup11 (p.Phe35TrpfsX41) results in a premature termination codon, predicted to cause a truncation of the encoded protein or absence of the protein due to nonsense mediated decay, which are commonly known mechanisms for disease. Truncations downstream of this position have been classified as pathogenic by our laboratory. The variant was absent in 198414 control chromosomes (gnomAD). c.93_103dup11 has been reported in the literature in individuals affected with Maple Syrup Urine Disease (Rodr-guez-Pombo_2006, Cheng_2017, Li_2018). These data indicate that the variant may be associated with disease. At least one publication reports experimental evidence evaluating an impact on protein function. The most pronounced variant effect results in 10%-<30% of normal BCKD activity (Rodr-guez-Pombo_2006). One ClinVar submitter (evaluation after 2014) cites the variant as pathogenic. Based on the evidence outlined above, the variant was classified as pathogenic. -

Maple syrup urine disease type 1A Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Baylor Genetics

Dec 23, 2023

- -

Computational scores

Source: dbNSFP v4.3

Splicing

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs398124601; hg19: chr6-80816489;