18-74291795-C-T

Variant summary

Our verdict is Likely pathogenic. Variant got 8 ACMG points: 8P and 0B. PVS1_Strong PM2 PP5_Moderate

The NM_148923.4(CYB5A):c.81G>A(p.Trp27Ter) variant causes a stop gained change. 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: CYB5A NM_148923.4 stop_gained
• Clinical Significance: Likely pathogenic criteria provided, single submitter P:2
• Conservation: PhyloP100: 6.01

Genes affected

CYB5A (HGNC:2570): (cytochrome b5 type A) The protein encoded by this gene is a membrane-bound cytochrome that reduces ferric hemoglobin (methemoglobin) to ferrous hemoglobin, which is required for stearyl-CoA-desaturase activity. Defects in this gene are a cause of type IV hereditary methemoglobinemia. Three transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Jun 2010]

ACMG classification

Verdict is Likely_pathogenic. Variant got 8 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. Fraction of 0.8 CDS is truncated, and there are 2 pathogenic variants in the truncated region.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 18-74291795-C-T is Pathogenic according to our data. Variant chr18-74291795-C-T is described in ClinVar as [Likely_pathogenic]. Clinvar id is 524200.Status of the report is criteria_provided_single_submitter, 1 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
CYB5A	NM_148923.4	c.81G>A	p.Trp27Ter	stop_gained	1/5	ENST00000340533.9
CYB5A	NM_001190807.3	c.81G>A	p.Trp27Ter	stop_gained	1/4
CYB5A	NM_001914.4	c.81G>A	p.Trp27Ter	stop_gained	1/6
CYB5A	XM_011525835.3	c.81G>A	p.Trp27Ter	stop_gained	1/4

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
CYB5A	ENST00000340533.9	c.81G>A	p.Trp27Ter	stop_gained	1/5	1	NM_148923.4	P1
CYB5A	ENST00000494131.6	c.81G>A	p.Trp27Ter	stop_gained	1/6	1
CYB5A	ENST00000397914.4	c.81G>A	p.Trp27Ter	stop_gained	1/4	3
CYB5A	ENST00000583418.1	n.163G>A		non_coding_transcript_exon_variant	1/4	2

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD4 exome Cov.: 31

GnomAD4 genome Cov.: 32

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, single submitter

Submissions by phenotype

Methemoglobinemia type 4 Pathogenic:2

Likely pathogenic, criteria provided, single submitter	curation	SIB Swiss Institute of Bioinformatics	Oct 15, 2018	This variant is interpreted as Likely Pathogenic, for Methemoglobinemia and ambiguous genitalia, autosomal recessive. The following ACMG Tag(s) were applied: PM2 => Absent from controls (or at extremely low frequency if recessive) in Exome Sequencing Project, 1000 Genomes Project, or Exome Aggregation Consortium. PVS1-Strong => PVS1 downgraded in strength to Strong. -
Pathogenic, no assertion criteria provided	literature only	OMIM	May 17, 2018	- -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
BayesDel_addAF	Pathogenic	0.62	D
BayesDel_noAF	Pathogenic	0.54
Cadd	Pathogenic	44
Dann	Uncertain	1.0
Eigen	Pathogenic	0.79
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Pathogenic	0.99	D
MutationTaster	Benign	1.0	A;A
Vest4		0.81
GERP RS		4.5

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

Publications

LitVar

Other links and lift over

dbSNP: rs1555691399; hg19: chr18-71959030;