rs1555418290

Variant names:

• chr15-90749506-A-G
• rs1555418290
• NM_000057.4:c.238A>G

Variant summary

Our verdict is Likely benign. The variant received -2 ACMG points: 0P and 2B. BP4_Moderate

The NM_000057.4(BLM):​c.238A>G​(p.Thr80Ala) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00000889 in 1,461,830 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 16/22 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. T80I) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000089 (0 hom.)
• Consequence: BLM NM_000057.4 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2
• Conservation: PhyloP100: -1.30
• Publications: 0 publications found

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 Gene-Disease associations (from GenCC):

• Bloom syndrome

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Myriad Women’s Health, Labcorp Genetics (formerly Invitae), G2P, Laboratory for Molecular Medicine, Orphanet, Genomics England PanelApp, ClinGen
• osteosarcoma

  Inheritance: AR Classification: MODERATE Submitted by: Genomics England PanelApp
• breast cancer

  Inheritance: AD Classification: NO_KNOWN Submitted by: Ambry Genetics
• hereditary nonpolyposis colon cancer

  Inheritance: AD Classification: NO_KNOWN Submitted by: Ambry Genetics

ACMG classification

Our verdict: Likely_benign. The variant received -2 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.074373275).

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
BLM	NM_000057.4	c.238A>G	p.Thr80Ala	missense_variant	Exon 3 of 22	ENST00000355112.8	NP_000048.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
BLM	ENST00000355112.8	c.238A>G	p.Thr80Ala	missense_variant	Exon 3 of 22	1	NM_000057.4	ENSP00000347232.3

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000889 AC: 13 AN: 1461830 Hom.: 0 Cov.: 31 AF XY: 0.00000963 AC XY: 7 AN XY: 727212

African (AFR) AF: 0.00 AC: 0 AN: 33480

American (AMR) AF: 0.0000224 AC: 1 AN: 44724

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26132

East Asian (EAS) AF: 0.00 AC: 0 AN: 39686

South Asian (SAS) AF: 0.00 AC: 0 AN: 86256

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53410

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5768

European-Non Finnish (NFE) AF: 0.0000108 AC: 12 AN: 1111980

Other (OTH) AF: 0.00 AC: 0 AN: 60394

GnomAD4 genome Cov.: 32

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Bloom syndrome Uncertain:1

Jun 05, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces threonine, which is neutral and polar, with alanine, which is neutral and non-polar, at codon 80 of the BLM protein (p.Thr80Ala). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with breast cancer (PMID: 23028338). ClinVar contains an entry for this variant (Variation ID: 454101). Algorithms developed to predict the effect of missense changes on protein structure and function output the following: SIFT: "Not Available"; PolyPhen-2: "Benign"; Align-GVGD: "Not Available". The alanine amino acid residue is found in multiple mammalian species, which suggests that this missense change does not adversely affect protein function. In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -

Hereditary cancer-predisposing syndrome Uncertain:1

Jun 06, 2025

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.T80A variant (also known as c.238A>G), located in coding exon 2 of the BLM gene, results from an A to G substitution at nucleotide position 238. The threonine at codon 80 is replaced by alanine, an amino acid with similar properties. This alteration was identified in an individual from a high risk breast cancer family (Thompson ER et al. PLoS Genet, 2012 Sep;8:e1002894). This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be tolerated by in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.060
BayesDel_addAF	Benign	-0.36	T
BayesDel_noAF	Benign	-0.75
CADD	Benign	0.14
DANN	Benign	0.38
DEOGEN2	Benign	0.062	T;.
Eigen	Benign	-1.4
Eigen_PC	Benign	-1.5
FATHMM_MKL	Benign	0.016	N
LIST_S2	Benign	0.50	T;T
M_CAP	Benign	0.0083	T
MetaRNN	Benign	0.074	T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	1.9	L;.
PhyloP100		-1.3
PrimateAI	Benign	0.26	T
PROVEAN	Benign	-0.42	N;N
REVEL	Benign	0.029
Sift	Benign	0.43	T;T
Sift4G	Benign	0.54	T;T
Polyphen		0.0	B;.
Vest4		0.056
MutPred		0.076		Loss of glycosylation at T80 (P = 0.0412);Loss of glycosylation at T80 (P = 0.0412);
MVP		0.58
MPC		0.087
ClinPred		0.030	T
GERP RS		-6.4
RBP_binding_hub_radar		0.0
RBP_regulation_power_radar		1.1
Varity_R		0.017
gMVP		0.056
Mutation Taster		=96/4	polymorphism

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

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

Other links and lift over

dbSNP: rs1555418290; hg19: chr15-91292736;