Genetic Variant HMBS:p.Arg116Trp (chr11-119089991-C-T) – ACMG Classification: Pathogenic (22 pts)

Variant summary

Our verdict is Pathogenic. The variant received 22 ACMG points: 22P and 0B. PS3PM1PM2PM5PP3_StrongPP5_Very_Strong

The NM_000190.4(HMBS):c.346C>T(p.Arg116Trp) variant causes a missense, splice region change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000031 in 1,612,738 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predict no significant impact on normal splicing. Variant has been reported in ClinVar as Pathogenic (★★). ClinVar reports functional evidence for this variant: "SCV004047777: This variant has been reported to affect HMBS protein function (Bustad et al., 2013)." and additional evidence is available in ClinVar. Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R116Q) has been classified as Likely pathogenic.

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000027 ( 0 hom. )

Consequence

HMBS
NM_000190.4 missense, splice_region

Scores

Splicing: ADA: 0.04952

Clinical Significance

Pathogenic criteria provided, multiple submitters, no conflicts P:6

Conservation

PhyloP100: 3.28

Publications

34 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, Labcorp Genetics (formerly Invitae), Orphanet, Genomics England PanelApp

HMBS links:

Genome browser will be placed here

new If you want to explore the variant's impact on the transcript NM_000190.4, check out the Mutation Effect Viewer. This is especially useful for frameshift variants or if you want to visualize the effect of exon loss / intron retention.

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 22 ACMG points.

PS3

PS3 evidence extracted from ClinVar submissions: SCV004047777: This variant has been reported to affect HMBS protein function (Bustad et al., 2013).; SCV001383626: Experimental studies have shown that this missense change affects HMBS function (PMID: 9281416, 23815679).; SCV002569876: Published functional studies demonstrate R116W abolishes enzymatic activity in vitro which is likely due to severe conformational instability of the variant (Bustad et al., 2013)

PM1

In a hotspot region, there are 2 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 8 uncertain in NM_000190.4

PM2

Very rare variant in population databases, with high coverage;

PM5

Other missense variant is known to change same aminoacid residue: Variant chr11-119089992-G-A is described in ClinVar as Conflicting_classifications_of_pathogenicity. ClinVar VariationId is 645809.

PP3

MetaRNN computational evidence supports a deleterious effect, 0.992

PP5

Variant 11-119089991-C-T is Pathogenic according to our data. Variant chr11-119089991-C-T is described in ClinVar as Pathogenic. ClinVar VariationId is 1445.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_000190.4. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
HMBS	NM_000190.4	MANE Select	c.346C>T	p.Arg116Trp	missense splice_region	Exon 7 of 14	NP_000181.2
HMBS	NM_001425056.1		c.346C>T	p.Arg116Trp	missense splice_region	Exon 7 of 14	NP_001411985.1
HMBS	NM_001425057.1		c.328C>T	p.Arg110Trp	missense splice_region	Exon 7 of 14	NP_001411986.1	A0A3F2YNY7

Ensembl Transcripts

Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
HMBS	ENST00000652429.1	MANE Select	c.346C>T	p.Arg116Trp	missense splice_region	Exon 7 of 14	ENSP00000498786.1	P08397-1
HMBS	ENST00000392841.1	TSL:1	c.295C>T	p.Arg99Trp	missense splice_region	Exon 7 of 14	ENSP00000376584.1	P08397-2
HMBS	ENST00000545621.5	TSL:1	n.*241C>T		splice_region non_coding_transcript_exon	Exon 7 of 10	ENSP00000444849.1	F5H4X2

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152188

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000241

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:

0.00

Gnomad OTH

AF:

0.00

GnomAD2 exomes

AF:

0.00000398

AC:

AN:

251466

AF XY:

0.00

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 FIN exome

AF:

0.00

Gnomad NFE exome

AF:

0.00000879

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.00000274

AC:

AN:

1460550

Hom.:

Cov.:

AF XY:

0.00000138

AC XY:

AN XY:

726714

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33464

American (AMR)

AF:

0.00

AC:

AN:

44722

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

26132

East Asian (EAS)

AF:

0.00

AC:

AN:

39696

South Asian (SAS)

AF:

0.00

AC:

AN:

86220

European-Finnish (FIN)

AF:

0.00

AC:

AN:

53420

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5762

European-Non Finnish (NFE)

AF:

0.00000360

AC:

AN:

1110786

Other (OTH)

AF:

0.00

AC:

AN:

60348

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.475

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome 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

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152188

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74342

show subpopulations

African (AFR)

AF:

0.0000241

AC:

AN:

41442

American (AMR)

AF:

0.00

AC:

AN:

15284

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5196

South Asian (SAS)

AF:

0.00

AC:

AN:

4836

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10616

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.00

AC:

AN:

68028

Other (OTH)

AF:

0.00

AC:

AN:

2086

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.625

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Alfa

AF:

0.00

Hom.:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.0000593

ClinVar

ClinVar submissions

Significance:Pathogenic

Revision:criteria provided, multiple submitters, no conflicts

View on ClinVar

Pathogenic

VUS

Benign

Condition

Acute intermittent porphyria (3)

not provided (3)

Computational scores

Source: dbNSFP v4.9

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.96

BayesDel_addAF

Pathogenic

0.55

BayesDel_noAF

Pathogenic

0.55

CADD

Pathogenic

(source)

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

1.0

Eigen

Pathogenic

0.80

Eigen_PC

Uncertain

0.65

FATHMM_MKL

Uncertain

0.89

M_CAP

Pathogenic

0.76

MetaRNN

Pathogenic

0.99

MetaSVM

Pathogenic

0.91

MutationAssessor

Pathogenic

4.5

PhyloP100

3.3

PrimateAI

Uncertain

0.66

PROVEAN

Pathogenic

-7.3

REVEL

Pathogenic

0.95

Sift

Pathogenic

0.0

Sift4G

Pathogenic

0.0

RBP_binding_hub_radar

0.92

RBP_regulation_power_radar

2.6

Varity_R

0.96

Mutation Taster

=9/91

disease causing (ClinVar)

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Benign

0.050

dbscSNV1_RF

Benign

0.29

Splicevardb

2.0

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

MaxEntScan Visualizer can be used to analyze the impact of this mutation on the neighboring sequence.

Publications

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HMBS p.Arg116Trp

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Variant Effect in Transcripts

RefSeq Transcripts

Ensembl Transcripts

Frequencies

Age Distribution

ClinVar

Computational scores

Splicing

Publications

Other links and lift over