rs772785079

Variant summary

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

The NM_000057.4(BLM):c.1968dup(p.Lys657GlufsTer5) variant causes a frameshift change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000372 in 1,613,940 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★). Variant results in nonsense mediated mRNA decay.

Frequency

Genomes: 𝑓 0.000013 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000027 ( 0 hom. )

Consequence

BLM
NM_000057.4 frameshift

Scores

Not classified

Clinical Significance

Pathogenic criteria provided, multiple submitters, no conflicts P:5

Conservation

PhyloP100: 7.89

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 15-90763050-T-TG is Pathogenic according to our data. Variant chr15-90763050-T-TG is described in ClinVar as [Pathogenic]. Clinvar id is 495425.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
BLM	NM_000057.4 linkuse as main transcript	c.1968dup	p.Lys657GlufsTer5	frameshift_variant	8/22	ENST00000355112.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
BLM	ENST00000355112.8 linkuse as main transcript	c.1968dup	p.Lys657GlufsTer5	frameshift_variant	8/22	1	NM_000057.4	P2

Frequencies

GnomAD3 genomes

AF:

0.0000131

AC:

AN:

152170

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000294

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000119

AC:

AN:

251206

Hom.:

AF XY:

0.0000221

AC XY:

AN XY:

135778

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.00

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.00

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.0000264

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000274

AC:

AN:

1461770

Hom.:

Cov.:

AF XY:

0.00000275

AC XY:

AN XY:

727202

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.00

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.00

Gnomad4 SAS exome

AF:

0.00

Gnomad4 FIN exome

AF:

0.00

Gnomad4 NFE exome

AF:

0.00000360

Gnomad4 OTH exome

AF:

0.00

GnomAD4 genome

AF:

0.0000131

AC:

AN:

152170

Hom.:

Cov.:

AF XY:

0.0000269

AC XY:

AN XY:

74336

show subpopulations

Gnomad4 AFR

AF:

0.00

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.0000294

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.0000434

Hom.:

Bravo

AF:

0.0000113

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:5

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Bloom syndrome

Pathogenic:4

Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Mar 16, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Dec 01, 2019	Variant summary: BLM c.1968dupG (p.Lys657GlufsX5) 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 allele was found at a frequency of 1.2e-05 in 251206 control chromosomes. c.1968dupG has been reported in the literature in at-least one homozygous individual born to consanguineous parents, affected with Bloom Syndrome and included in the Bloom syndrome registry (German_2007). It has subsequently been cited as a pathogenic variant in reports of carrier screening for BLM syndrome (Perreault-Micale_2015) and other literature (de Voer_2015, Salah_2014). These data indicate that the variant is likely to be associated with disease. To our knowledge, no experimental evidence demonstrating an impact on protein function has been reported. The variant has been observed at-least twice among individuals undergoing carrier screening at our laboratory. No other clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar after 2014. Based on the evidence outlined above, the variant was re-classified as pathogenic. -
Likely pathogenic, no assertion criteria provided	clinical testing	Counsyl	Mar 16, 2015	- -
Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Dec 27, 2023	This sequence change creates a premature translational stop signal (p.Lys657Glufs*5) 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 (rs772785079, gnomAD 0.002%). This premature translational stop signal has been observed in individual(s) with Bloom syndrome (PMID: 17407155). ClinVar contains an entry for this variant (Variation ID: 495425). RNA analysis performed to evaluate the impact of this premature translational stop signal on mRNA splicing indicates it does not significantly alter splicing (Invitae). For these reasons, this variant has been classified as Pathogenic. -

Hereditary cancer-predisposing syndrome

Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Ambry Genetics

Feb 27, 2023

The c.1968dupG pathogenic mutation, located in coding exon 7 of the BLM gene, results from a duplication of G at nucleotide position 1968, causing a translational frameshift with a predicted alternate stop codon (p.K657Efs*5). This alteration has been reported in a cohort of 134 persons with Bloom syndrome (BS) from the Bloom's Syndrome Registry (German J et al. Hum. Mutat., 2007 Aug;28:743-53). 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)

0.020

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