Genetic Variant HMBS:c.33+129_33+135delTTTTTTT (chr11-119085172-CTTTTTTT-C) – ACMG Classification: Benign (-8 pts)

Variant summary

Our verdict is Benign. The variant received -8 ACMG points: 0P and 8B. BS1BS2

The NM_000190.4(HMBS):c.33+129_33+135delTTTTTTT variant causes a intron change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.00973 in 794,732 control chromosomes in the GnomAD database, including 5 homozygotes. No clinical diagnostic laboratories have submitted clinical-significance assessments for this variant to ClinVar.

Frequency

Genomes: 𝑓 0.00085 ( 0 hom., cov: 0)

Exomes 𝑓: 0.011 ( 5 hom. )

Consequence

HMBS
NM_000190.4 intron

Scores

Not classified

Clinical Significance

Not reported in ClinVar

Conservation

PhyloP100: 1.83

Publications

0 publications found

Variant links:

Genes affected

HMBS (HGNC:4982): (hydroxymethylbilane synthase) This gene encodes a member of the hydroxymethylbilane synthase superfamily. The encoded protein is the third enzyme of the heme biosynthetic pathway and catalyzes the head to tail condensation of four porphobilinogen molecules into the linear hydroxymethylbilane. Mutations in this gene are associated with the autosomal dominant disease acute intermittent porphyria. Alternatively spliced transcript variants encoding different isoforms have been described. [provided by RefSeq, Jul 2008]

HMBS Gene-Disease associations (from GenCC):

acute intermittent porphyria
Inheritance: SD, AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: ClinGen, Genomics England PanelApp, Labcorp Genetics (formerly Invitae), Orphanet

HMBS links:

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ACMG classification

Classification was made for transcript

Our verdict: Benign. The variant received -8 ACMG points.

BS1

Variant frequency is greater than expected in population eas. GnomAd4 allele frequency = 0.000853 (57/66804) while in subpopulation EAS AF = 0.00997 (14/1404). AF 95% confidence interval is 0.00603. There are 0 homozygotes in GnomAd4. There are 30 alleles in the male GnomAd4 subpopulation. Median coverage is 0. This position passed quality control check.

BS2

High AC in GnomAd4 at 57 SD,AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HMBS	NM_000190.4 link	c.33+129_33+135delTTTTTTT		intron_variant	Intron 1 of 13	ENST00000652429.1	NP_000181.2	P08397-1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HMBS	ENST00000652429.1 link	c.33+107_33+113delTTTTTTT		intron_variant	Intron 1 of 13		NM_000190.4	ENSP00000498786.1		P08397-1

Frequencies

GnomAD3 genomes

AF:

0.000854

AC:

AN:

66768

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.000381

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.000626

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00999

Gnomad SAS

AF:

0.00229

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.000828

Gnomad OTH

AF:

0.00

GnomAD4 exome

AF:

0.0105

AC:

7676

AN:

727928

Hom.:

AF XY:

0.0106

AC XY:

3825

AN XY:

359898

show subpopulations

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

African (AFR)

AF:

0.0120

AC:

220

AN:

18258

American (AMR)

AF:

0.00786

AC:

AN:

11710

Ashkenazi Jewish (ASJ)

AF:

0.00767

AC:

AN:

10300

East Asian (EAS)

AF:

0.0246

AC:

191

AN:

7756

South Asian (SAS)

AF:

0.0159

AC:

781

AN:

49246

European-Finnish (FIN)

AF:

0.00752

AC:

AN:

11300

Middle Eastern (MID)

AF:

0.00889

AC:

AN:

1912

European-Non Finnish (NFE)

AF:

0.0100

AC:

5910

AN:

590030

Other (OTH)

AF:

0.0110

AC:

301

AN:

27416

⚠️ The allele balance in gnomAD4 Exomes is highly skewed from 0.5 (p-value = 0), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.329

Heterozygous variant carriers

481

962

1442

1923

2404

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Exome Hom

Variant carriers

262

524

786

1048

1310

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.000853

AC:

AN:

66804

Hom.:

Cov.:

AF XY:

0.00102

AC XY:

AN XY:

29542

show subpopulations

African (AFR)

AF:

0.000380

AC:

AN:

18402

American (AMR)

AF:

0.000626

AC:

AN:

4796

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

2142

East Asian (EAS)

AF:

0.00997

AC:

AN:

1404

South Asian (SAS)

AF:

0.00229

AC:

AN:

1308

European-Finnish (FIN)

AF:

0.00

AC:

AN:

1126

Middle Eastern (MID)

AF:

0.00

AC:

AN:

European-Non Finnish (NFE)

AF:

0.000828

AC:

AN:

36234

Other (OTH)

AF:

0.00

AC:

AN:

858

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.498

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Genome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

Alfa

AF:

0.00

Hom.:

ClinVar

Not reported in ClinVar

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

PhyloP100

1.8

Mutation Taster

=100/0

polymorphism

(source)

Splicing

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

Publications

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11-119085172-CTTTTTTTTTTTTTTTTTTTTTT-CTTTTTTTTTTTTTTT

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over