NM_000190.4:c.77G>C

Variant names:

• chr11-119088298-G-C
• rs118204103
• NM_000190.4:c.77G>C

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PM2 PP3_Strong PP5_Moderate

The NM_000190.4(HMBS):​c.77G>C​(p.Arg26Pro) variant causes a missense change involving the alteration of a conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★).

• Frequency: Genomes: not found (cov: 32)
• Consequence: HMBS NM_000190.4 missense
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:1
• Conservation: PhyloP100: 7.97

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]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.989
• PP5: Variant 11-119088298-G-C is Pathogenic according to our data. Variant chr11-119088298-G-C is described in ClinVar as [Likely_pathogenic]. Clinvar id is 945373.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
HMBS	NM_000190.4	c.77G>C	p.Arg26Pro	missense_variant	Exon 2 of 14	ENST00000652429.1	NP_000181.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
HMBS	ENST00000652429.1	c.77G>C	p.Arg26Pro	missense_variant	Exon 2 of 14		NM_000190.4	ENSP00000498786.1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:1

Revision: criteria provided, single submitter

Submissions by phenotype

not provided Pathogenic:1

Mar 10, 2023

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

In summary, the currently available evidence indicates that the variant is pathogenic, but additional data are needed to prove that conclusively. Therefore, this variant has been classified as Likely Pathogenic. This sequence change replaces arginine, which is basic and polar, with proline, which is neutral and non-polar, at codon 26 of the HMBS protein (p.Arg26Pro). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with clinical features of acute intermittent porphyria (Invitae). ClinVar contains an entry for this variant (Variation ID: 945373). Advanced modeling of protein sequence and biophysical properties (such as structural, functional, and spatial information, amino acid conservation, physicochemical variation, residue mobility, and thermodynamic stability) performed at Invitae indicates that this missense variant is expected to disrupt HMBS protein function. This variant disrupts the p.Arg26 amino acid residue in HMBS. Other variant(s) that disrupt this residue have been determined to be pathogenic (PMID: 8401516, 26095755, 26582343). This suggests that this residue is clinically significant, and that variants that disrupt this residue are likely to be disease-causing. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.59	D
BayesDel_noAF	Pathogenic	0.61
CADD	Pathogenic	34
DANN	Uncertain	1.0
DEOGEN2	Pathogenic	1.0	.;D;.;.;D;.;.;.;.;.;.;.
Eigen	Pathogenic	1.1
Eigen_PC	Pathogenic	1.0
FATHMM_MKL	Pathogenic	0.99	D
M_CAP	Pathogenic	0.73	D
MetaRNN	Pathogenic	0.99	D;D;D;D;D;D;D;D;D;D;D;D
MetaSVM	Pathogenic	0.92	D
MutationAssessor	Pathogenic	4.5	.;H;.;.;.;.;H;.;.;.;.;.
PrimateAI	Uncertain	0.72	T
PROVEAN	Pathogenic	-6.2	.;D;D;D;D;.;D;.;D;D;D;.
REVEL	Pathogenic	0.96
Sift	Uncertain	0.0010	.;D;D;D;D;.;D;.;D;D;D;.
Sift4G	Pathogenic	0.0	.;D;D;D;D;.;D;.;D;D;D;.
Polyphen		1.0	.;D;.;.;.;.;.;.;.;.;.;.
Vest4		0.97, 0.97, 0.96, 0.95, 0.97
MutPred		0.93		Gain of glycosylation at R26 (P = 0.0164);Gain of glycosylation at R26 (P = 0.0164);.;.;Gain of glycosylation at R26 (P = 0.0164);.;Gain of glycosylation at R26 (P = 0.0164);.;.;.;.;.;
MVP		0.98
MPC		1.4
ClinPred		1.0	D
GERP RS		5.5
Varity_R		0.99

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.17		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: rs118204103; hg19: chr11-118959008;