16-177038-A-G

Variant names:

• chr16-177038-A-G
• rs34823698
• NM_000558.5:c.205A>G

Variant summary

Our verdict is Uncertain significance. The variant received 2 ACMG points: 2P and 0B. PM2

The NM_000558.5(HBA1):​c.205A>G​(p.Asn69Asp) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. 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. N69K) has been classified as Uncertain significance.

• Frequency:
  • Genomes: not found (cov: 31)
  • Exomes 𝑓: 0.0000015 (0 hom.)
  • Failed GnomAD Quality Control
• Consequence: HBA1 NM_000558.5 missense
• Clinical Significance: Uncertain significance criteria provided, multiple submitters, no conflicts U:2 O:1
• Conservation: PhyloP100: -0.0580
• Publications: 6 publications found

Genes affected

HBA1 (HGNC:4823): (hemoglobin subunit alpha 1) The human alpha globin gene cluster located on chromosome 16 spans about 30 kb and includes seven loci: 5'- zeta - pseudozeta - mu - pseudoalpha-1 - alpha-2 - alpha-1 - theta - 3'. The alpha-2 (HBA2) and alpha-1 (HBA1) coding sequences are identical. These genes differ slightly over the 5' untranslated regions and the introns, but they differ significantly over the 3' untranslated regions. Two alpha chains plus two beta chains constitute HbA, which in normal adult life comprises about 97% of the total hemoglobin; alpha chains combine with delta chains to constitute HbA-2, which with HbF (fetal hemoglobin) makes up the remaining 3% of adult hemoglobin. Alpha thalassemias result from deletions of each of the alpha genes as well as deletions of both HBA2 and HBA1; some nondeletion alpha thalassemias have also been reported. [provided by RefSeq, Jul 2008]

HBA1 Gene-Disease associations (from GenCC):

• alpha thalassemia spectrum

  Inheritance: AR, SD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics
• erythrocytosis, familial, 7

  Inheritance: AD Classification: STRONG Submitted by: Genomics England PanelApp
• hemoglobin M disease

  Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
• Hb Bart's hydrops fetalis

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• hemoglobin H disease

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet
• methemoglobinemia, alpha type

  Inheritance: AD Classification: LIMITED Submitted by: ClinGen
• Heinz body anemia

  Inheritance: AR Classification: LIMITED Submitted by: Labcorp Genetics (formerly Invitae)

ENSG00000294436 (HGNC:):

ACMG classification

Our verdict: Uncertain_significance. The variant received 2 ACMG points.

• PM2: Very rare variant in population databases, with high coverage

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000558.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	HBA1	NM_000558.5	MANE Select	c.205A>G	p.Asn69Asp	missense	Exon 2 of 3	NP_000549.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	HBA1	ENST00000320868.9	TSL:1 MANE Select	c.205A>G	p.Asn69Asp	missense	Exon 2 of 3	ENSP00000322421.5
	HBA1	ENST00000472694.1	TSL:1	n.341A>G		non_coding_transcript_exon	Exon 1 of 2
	HBA1	ENST00000487791.1	TSL:1	n.174A>G		non_coding_transcript_exon	Exon 2 of 2

Frequencies

GnomAD3 genomes Cov.: 31

GnomAD4 exome Data not reliable, filtered out with message: AS_VQSR AF: 0.00000152 AC: 2 AN: 1313466 Hom.: 0 Cov.: 22 AF XY: 0.00000307 AC XY: 2 AN XY: 652514

⚠️ The allele balance in gnomAD version 4 Exomes is significantly skewed from the expected value of 0.5.

African (AFR) AF: 0.00 AC: 0 AN: 30220

American (AMR) AF: 0.00 AC: 0 AN: 36334

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 24708

East Asian (EAS) AF: 0.0000280 AC: 1 AN: 35760

South Asian (SAS) AF: 0.00 AC: 0 AN: 79394

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 34744

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 3956

European-Non Finnish (NFE) AF: 9.87e-7 AC: 1 AN: 1012946

Other (OTH) AF: 0.00 AC: 0 AN: 55404

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0.000203476), which strongly suggests a high chance of mosaicism in these individuals.

GnomAD4 genome Cov.: 31

ClinVar

Significance: Uncertain significance

Submissions summary: Uncertain:2 Other:1

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

not specified Uncertain:1

Jun 05, 2025

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

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: HBA1 c.205A>G (p.Asn69Asp) results in a conservative amino acid change located in the Globin domain (IPR000971) of the encoded protein sequence. Algorithms developed to predict the effect of missense changes on protein structure and function all suggest that this variant is likely to be tolerated. The variant was absent in 136744 control chromosomes. The available data on variant occurrences in the general population are insufficient to allow any conclusion about variant significance. c.205A>G (also known as Hb Ube 2) has been reported in the literature as in multiple individuals without evidence of cosegregation with disease (e.g. Miyaji_1967, Bilginer_1984, Shin_2002, Lou_2014). These reports do not provide unequivocal conclusions about association of the variant with Alpha Thalassemia. At least one publication reports experimental evidence evaluating an impact on protein function, finding no effect of the variant on oxygen affinity, Bohr effect, or heme heme interaction (Imai_1970). The following publications have been ascertained in the context of this evaluation (PMID: 6035181, 6469696, 5416123, 11939522, 24985555). ClinVar contains an entry for this variant (Variation ID: 15831). Based on the evidence outlined above, the variant was classified as uncertain significance.

not provided Uncertain:1

Jun 03, 2021

Quest Diagnostics Nichols Institute San Juan Capistrano

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

HEMOGLOBIN UBE-2 Other:1

Jul 20, 2016

OMIM

Significance: other

Review Status: no assertion criteria provided

Collection Method: literature only

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.12
BayesDel_addAF	Uncertain	0.072	D
BayesDel_noAF	Benign	-0.13
CADD	Benign	1.4
DANN	Benign	0.66
DEOGEN2	Benign	0.079	T
Eigen	Benign	-1.7
Eigen_PC	Benign	-1.9
FATHMM_MKL	Benign	0.035	N
LIST_S2	Benign	0.75	T
M_CAP	Pathogenic	0.29	D
MetaRNN	Uncertain	0.67	D
MetaSVM	Benign	-0.44	T
PhyloP100		-0.058
PrimateAI	Benign	0.43	T
PROVEAN	Benign	0.17	N
REVEL	Uncertain	0.39
Sift	Uncertain	0.013	D
Sift4G	Benign	0.78	T
Vest4		0.55
MutPred		0.75		Gain of disorder (P = 0.093)
MVP		0.94
ClinPred		0.093	T
GERP RS		-8.6
PromoterAI		0.0018	Neutral
Varity_R		0.36
gMVP		0.78
Mutation Taster		=9/91	disease causing

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

Other links and lift over

dbSNP: rs34823698; hg19: chr16-227037;