dbSNP rs367543013: BLM:p.Leu258GlufsTer7 (chr15-90750035-ACT-A) – ACMG Classification: Pathogenic (18 pts)

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1PM2PP5_Very_Strong

The NM_000057.4(BLM):c.772_773delCT(p.Leu258GlufsTer7) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000143 in 1,613,978 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: 𝑓 0.000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000089 ( 0 hom. )

Consequence

BLM
NM_000057.4 frameshift

Scores

Not classified

Clinical Significance

Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:12

Conservation

PhyloP100: 0.193

Variant links:

Genes affected

BLM (HGNC:1058): (BLM RecQ like helicase) The Bloom syndrome is an autosomal recessive disorder characterized by growth deficiency, microcephaly and immunodeficiency among others. It is caused by homozygous or compound heterozygous mutation in the gene encoding DNA helicase RecQ protein on chromosome 15q26. This Bloom-associated helicase unwinds a variety of DNA substrates including Holliday junction, and is involved in several pathways contributing to the maintenance of genome stability. Identification of pathogenic Bloom variants is required for heterozygote testing in at-risk families. [provided by RefSeq, May 2020]

BLM links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

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 15-90750035-ACT-A is Pathogenic according to our data. Variant chr15-90750035-ACT-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 42092.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BLM	NM_000057.4 link	c.772_773delCT	p.Leu258GlufsTer7	frameshift_variant	Exon 3 of 22	ENST00000355112.8	NP_000048.1	P54132

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8 link	c.772_773delCT	p.Leu258GlufsTer7	frameshift_variant	Exon 3 of 22	1	NM_000057.4	ENSP00000347232.3		P54132

Frequencies

GnomAD3 genomes

AF:

0.0000657

AC:

AN:

152130

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000121

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000131

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.000207

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000294

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000321

AC:

AN:

249258

Hom.:

AF XY:

0.0000296

AC XY:

AN XY:

135098

show subpopulations

Gnomad AFR exome

AF:

0.000191

Gnomad AMR exome

AF:

0.0000289

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000544

Gnomad SAS exome

AF:

0.0000327

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000178

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000889

AC:

AN:

1461848

Hom.:

AF XY:

0.00000825

AC XY:

AN XY:

727220

show subpopulations

Gnomad4 AFR exome

AF:

0.0000896

Gnomad4 AMR exome

AF:

0.0000224

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.0000756

Gnomad4 SAS exome

AF:

0.0000116

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000450

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000657

AC:

AN:

152130

Hom.:

Cov.:

AF XY:

0.0000538

AC XY:

AN XY:

74320

show subpopulations

Gnomad4 AFR

AF:

0.000121

Gnomad4 AMR

AF:

0.000131

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.000207

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000294

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000712

Hom.:

Bravo

AF:

0.0000453

EpiCase

AF:

0.0000545

EpiControl

AF:

0.00

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:12

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Bloom syndrome

Pathogenic:9

Dec 20, 2023

Fulgent Genetics, Fulgent Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Mar 12, 2021

New York Genome Center

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Mar 30, 2024

Baylor Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Juno Genomics, Hangzhou Juno Genomics, Inc

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

PVS1+PM2_Supporting+PM3_Strong+PP1+PP4 -

Mar 17, 2017

Natera, Inc.

Significance: Pathogenic

Review Status: no assertion criteria provided

Collection Method: clinical testing

- -

Apr 24, 2017

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: The BLM c.772_773delCT (p.Leu258Glufs) variant results in a premature termination codon, predicted to cause a truncated or absent BLM 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 (e.g. c.2207_2212delinsTAGATTC (p.Tyr736fs) and c.1642C>T (p.Gln548X)). One in silico tool predicts a damaging outcome for this variant. This variant was found in 5/119222 control chromosomes at a frequency of 0.0000419, which does not exceed the estimated maximal expected allele frequency of a pathogenic BLM variant (0.0035355). The variant has been reported in at least one homozygous affected individual in the literature. In addition, multiple clinical diagnostic laboratories/reputable databases classified this variant as likely pathogenic/pathogenic. Taken together, this variant is classified as "pathogenic." -

Dec 19, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change creates a premature translational stop signal (p.Leu258Glufs*7) in the BLM gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in BLM are known to be pathogenic (PMID: 17407155). This variant is present in population databases (rs760209332, gnomAD 0.02%). This premature translational stop signal has been observed in individual(s) with Bloom syndrome and breast and ovarian cancer (PMID: 17407155, 24448499, 28724667). This variant is also known as c.768_769del, p.D256fs. ClinVar contains an entry for this variant (Variation ID: 42092). For these reasons, this variant has been classified as Pathogenic. -

Jun 04, 2014

Counsyl

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: literature only

- -

Sep 06, 2024

St. Jude Molecular Pathology, St. Jude Children's Research Hospital

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The BLM c.772_773del (p.Leu258GlufsTer7) change deletes two nucleotides to cause a frameshift and the creation of a premature stop codon. This change is predicted to cause protein truncation or absence of protein due to nonsense-mediated decay. This variant has been observed in an individual with Bloom syndrome (PMID: 17407155). This variant has a maximum subpopulation frequency of 0.02% in gnomAD v2.1.1 (https://gnomad.broadinstitute.org). In summary, this variant meets criteria to be classified as pathogenic. -

not provided

Pathogenic:2

Jul 06, 2023

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant alters the translational reading frame of the BLM mRNA and causes the premature termination of BLM protein synthesis. In the published literature, this variant has been reported in individuals with breast cancer (PMID: 36315097 (2022), 28724667 (2017)), rectal cancer (PMID: 29625052 (2018)), colorectal cancer (PMID: 29478780 (2018)), lung cancer (PMID: 35273153 (2022), 31721094 (2020)), and astrocytoma (PMID: 32783018 (2019), 31133068 (2019)). This variant has also been observed in individuals with Bloom Syndrome (PMID: 29783825 (2018), 17407155 (2007)). The frequency of this variant in the general population, 0.00016 (4/24446 chromosomes (Genome Aggregation Database, http://gnomad.broadinstitute.org)), is consistent with pathogenicity. Based on the available information, this variant is classified as pathogenic. -

Oct 07, 2022

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Frameshift variant predicted to result in protein truncation or nonsense mediated decay in a gene for which loss of function is a known mechanism of disease; Identified in the heterozygous state in individuals with breast, ovarian, or colorectal cancer (Kanchi et al., 2014; Sun et al., 2017; Huang et al., 2018); This variant is associated with the following publications: (PMID: 26247052, 17407155, 24448499, 28724667, 29625052, 29783825, 29478780, 31721094) -

Hereditary cancer-predisposing syndrome

Pathogenic:1

May 29, 2024

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.772_773delCT pathogenic mutation, located in coding exon 2 of the BLM gene, results from a deletion of two nucleotides at nucleotide positions 772 to 773, causing a translational frameshift with a predicted alternate stop codon (p.L258Efs*7). This mutation has been reported in the homozygous and compound heterozygous states in patients with Bloom syndrome (German J et al. Hum Mutat, 2007 Aug;28:743-53; Wu ML et al. Zhonghua Er Ke Za Zhi, 2018 May;56:373-376). This mutation has also been reported in a patient with ovarian cancer (Kanchi KL et al. Nat Commun, 2014;5:3156). In addition to the clinical data presented in the literature, this alteration is expected to result in loss of function by premature protein truncation or nonsense-mediated mRNA decay. As such, this alteration is interpreted as a disease-causing mutation. -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

Splicing

Name

Calibrated prediction

Score

Prediction

SpliceAI score (max)

0.0

Details are displayed if max score is > 0.2

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

Publications

LitVar

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over