11-5226975-CA-C

Position:

• chr11-5226975-CA-C

Variant summary

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

The ENST00000335295.4(HBB):​c.46del​(p.Trp16GlyfsTer4) variant causes a frameshift change. The variant allele was found at a frequency of 0.00000137 in 1,461,398 control chromosomes in the GnomAD database, with no homozygous occurrence. Variant has been reported in ClinVar as Pathogenic (★★).

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000014 (0 hom.)
• Consequence: HBB ENST00000335295.4 frameshift
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:8
• Conservation: PhyloP100: 5.41

Genes affected

HBB (HGNC:4827): (hemoglobin subunit beta) The alpha (HBA) and beta (HBB) loci determine the structure of the 2 types of polypeptide chains in adult hemoglobin, Hb A. The normal adult hemoglobin tetramer consists of two alpha chains and two beta chains. Mutant beta globin causes sickle cell anemia. Absence of beta chain causes beta-zero-thalassemia. Reduced amounts of detectable beta globin causes beta-plus-thalassemia. The order of the genes in the beta-globin cluster is 5'-epsilon -- gamma-G -- gamma-A -- delta -- beta--3'. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product does not undergo nonsense mediated mRNA decay. Variant located near the start codon (<100nt), not predicted to undergo nonsense mediated mRNA decay. There are 344 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 11-5226975-CA-C is Pathogenic according to our data. Variant chr11-5226975-CA-C is described in ClinVar as [Pathogenic]. Clinvar id is 38647.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr11-5226975-CA-C is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
HBB	NM_000518.5	c.46del	p.Trp16GlyfsTer4	frameshift_variant	1/3	ENST00000335295.4	NP_000509.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
HBB	ENST00000335295.4	c.46del	p.Trp16GlyfsTer4	frameshift_variant	1/3	1	NM_000518.5	ENSP00000333994	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome AF: 0.00000137 AC: 2 AN: 1461398 Hom.: 0 Cov.: 33 AF XY: 0.00000275 AC XY: 2 AN XY: 727030

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: 0.0000116

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.0000166

GnomAD4 genome Cov.: 32

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:8

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

beta Thalassemia Pathogenic:4

Pathogenic, no assertion criteria provided	clinical testing	Natera, Inc.	Mar 17, 2017	- -
Pathogenic, criteria provided, single submitter	clinical testing	Women's Health and Genetics/Laboratory Corporation of America, LabCorp	Aug 23, 2017	Variant summary: The HBB c.46delT (p.Trp16Glyfs) variant results in a premature termination codon, predicted to cause a truncated or absent HBB 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.51delC [p.Lys18fs). MutationTaster predicts a damaging outcome for this variant. The variant has been identified in numerous patients, including homozygotes, and is a relatively common disease-associated mutation in South Asian and Indonesian populations. This variant is absent in 121364 control chromosomes (ExAC). Taken together, this variant is classified as pathogenic. -
Pathogenic, no assertion criteria provided	curation	The ITHANET community portal, The Cyprus Institute of Neurology and Genetics	Nov 25, 2019	- -
Pathogenic, no assertion criteria provided	clinical testing	Counsyl	Aug 16, 2017	- -

not provided Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Quest Diagnostics Nichols Institute San Juan Capistrano	Sep 15, 2022	The HBB c.46del (p.Trp16Glyfs*4) variant (also known as Codon 15 (-T)) alters the translational reading frame of the HBB mRNA and causes the premature termination of HBB protein synthesis. This variant is associated with beta(0)-thalassemia (PMIDs: 2120891 (1990), 26402558 (2015), 27117567 (2016)). Based on the available information, this variant is classified as pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Oct 25, 2023	This sequence change creates a premature translational stop signal (p.Trp16Glyfs*4) in the HBB gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in HBB are known to be pathogenic (PMID: 23637309). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individuals with beta thalassemia (PMID: 7928376, 28680605). This variant is also known as CD 15 (-T). ClinVar contains an entry for this variant (Variation ID: 38647). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -
Pathogenic, criteria provided, single submitter	clinical testing	ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories	Jan 03, 2022	The HBB c.46delT; p.Trp16GlyfsTer4 variant (rs63749960), also known as Codon 15(-T), is reported in the literature in multiple individuals affected with beta0- thalassemia (see HbVar and references therein, Baysal 1994, Kelkar 2017). This variant is reported in ClinVar (Variation ID: 38647) and is absent from the Genome Aggregation Database, indicating it is not a common polymorphism. This variant causes a frameshift by deleting a single nucleotide, so it is predicted to result in a truncated protein or mRNA subject to nonsense-mediated decay. Based on available information, this variant is considered to be pathogenic. References: Link to HbVar for Codon 15 (-T): https://globin.bx.psu.edu/cgi-bin/hbvar/query_vars3?mode=output&display_format=page&i=798&.cgifields=histD Baysal E et al. Distribution of beta-thalassemia mutations in three Asian Indian populations with distant geographical locations. Hemoglobin. 1994 May;18(3):201-9. PMID: 7928376. Kelkar AJ et al. Thalassemia intermedia phenotype resulting from rare combination of c.46delT (Codon15 (-T)) mutation of beta globin gene and HPFH3. Clin Case Rep. 2017 May 26;5(7):1107-1110. PMID: 28680605. -

Beta-thalassemia HBB/LCRB Pathogenic:1

Pathogenic, no assertion criteria provided

clinical testing

MOLECULAR BIOLOGY AND HUMAN GENETICS DIVISION, THE UNIVERSITY OF BURDWAN

May 07, 2024

The variant HBB:c.46delT (NP_000509.1:p.Trp16fs ) is a beta zero type of mutation. This is a frameshift mutation by deleting a single nuecleotide base and resulting in truncated mRNA. When this variant present in homozygous or in compound heterozygous with other beta 0 / beta + mutation leads to severe type of thalassemia. Patients needing monthly transfusion, often presented with hepatosplenomegaly, Iron overload. The frequency of the variant among thalassemia patient in Eastern India is 1.39% as per our multicentric project - A Genetic Diagnostic Algorithm Based Study for Thalassemia in Northern and Eastern Indian Populations, Funded by Dept. of Biotechnology , Govt of India [Project No. BT/PR26461/MED/12/821/2018] -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.030		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

Other links and lift over

dbSNP: rs63749960; hg19: chr11-5248205;