rs80338784

chr17-63959278-C-T

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PM1 PM2 PM5 PP3_Strong PP5_Very_Strong

The NM_000334.4(SCN4A):c.2006G>A(p.Arg669His) variant causes a missense change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000205 in 1,461,012 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 13/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R669C) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 32)
  • Exomes 𝑓: 0.0000021 (0 hom.)
• Consequence: SCN4A NM_000334.4 missense
• Clinical Significance: Pathogenic criteria provided, multiple submitters, no conflicts P:3 O:2
• Conservation: PhyloP100: 7.87

Genes affected

SCN4A (HGNC:10591): (sodium voltage-gated channel alpha subunit 4) Voltage-gated sodium channels are transmembrane glycoprotein complexes composed of a large alpha subunit with 24 transmembrane domains and one or more regulatory beta subunits. They are responsible for the generation and propagation of action potentials in neurons and muscle. This gene encodes one member of the sodium channel alpha subunit gene family. It is expressed in skeletal muscle, and mutations in this gene have been linked to several myotonia and periodic paralysis disorders. [provided by RefSeq, Jul 2008]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PM1: In a hotspot region, there are 5 aminoacids with missense pathogenic changes in the window of +-8 aminoacids around while only 0 benign, 6 uncertain in NM_000334.4
• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr17-63959279-G-A is described in ClinVar as [Likely_pathogenic]. Clinvar id is 843445.Status of the report is criteria_provided_single_submitter, 1 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.992
• PP5: Variant 17-63959278-C-T is Pathogenic according to our data. Variant chr17-63959278-C-T is described in ClinVar as [Pathogenic]. Clinvar id is 5911.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars. Variant chr17-63959278-C-T is described in Lovd as [Pathogenic].

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
SCN4A	NM_000334.4	c.2006G>A	p.Arg669His	missense_variant	12/24	ENST00000435607.3

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
SCN4A	ENST00000435607.3	c.2006G>A	p.Arg669His	missense_variant	12/24	1	NM_000334.4	P1

Frequencies

GnomAD3 genomes Cov.: 32

GnomAD3 exomes AF: 0.00000805 AC: 2 AN: 248518 Hom.: 0 AF XY: 0.0000148 AC XY: 2 AN XY: 134772

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 SAS exome AF: 0.00

Gnomad FIN exome AF: 0.0000930

Gnomad NFE exome AF: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.00000205 AC: 3 AN: 1461012 Hom.: 0 Cov.: 32 AF XY: 0.00000275 AC XY: 2 AN XY: 726742

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.0000562

Gnomad4 NFE exome AF: 0.00

Gnomad4 OTH exome AF: 0.00

GnomAD4 genome Cov.: 32

Alfa AF: 0.000146 Hom.: 0

ExAC AF: 0.00000826 AC: 1

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:3 Other:2

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Hypokalemic periodic paralysis, type 2 Pathogenic:1 Other:1

Pathogenic, no assertion criteria provided	literature only	OMIM	Apr 01, 2002	- -
not provided, no classification provided	literature only	GeneReviews	-	- -

Hyperkalemic periodic paralysis Pathogenic:1 Other:1

Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Dec 17, 2021	For these reasons, this variant has been classified as Pathogenic. Experimental studies have shown that this missense change affects SCN4A function (PMID: 11102465, 11912116, 21881211, 25024265). Algorithms developed to predict the effect of missense changes on protein structure and function (SIFT, PolyPhen-2, Align-GVGD) all suggest that this variant is likely to be disruptive. ClinVar contains an entry for this variant (Variation ID: 5911). This missense change has been observed in individual(s) with hypokalemic periodic paralysis (PMID: 10599760, 18162704, 21841462). In at least one individual the variant was observed to be de novo. It has also been observed to segregate with disease in related individuals. This variant is present in population databases (rs80338784, gnomAD 0.009%). This sequence change replaces arginine, which is basic and polar, with histidine, which is basic and polar, at codon 669 of the SCN4A protein (p.Arg669His). -
not provided, no classification provided	literature only	GeneReviews	-	- -

not provided Pathogenic:1

Pathogenic, criteria provided, single submitter

clinical testing

Athena Diagnostics

Mar 21, 2023

The frequency of this variant in the general population is consistent with pathogenicity (http://gnomad.broadinstitute.org). This variant appears to occur de novo in multiple individuals with clinical features of hypokalemic periodic paralysis. Assessment of experimental evidence suggests this variant results in abnormal protein function. (PMID: 11102465, 11912116, 21881211, 25024265) The variant is located in a region that is considered important for protein function and/or structure. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.99
BayesDel_addAF	Pathogenic	0.58	D
BayesDel_noAF	Pathogenic	0.60
Cadd	Pathogenic	31
Dann	Pathogenic	1.0
DEOGEN2	Pathogenic	0.98	D
Eigen	Pathogenic	1.0
Eigen_PC	Pathogenic	0.90
FATHMM_MKL	Pathogenic	0.97	D
LIST_S2	Uncertain	0.96	D
M_CAP	Pathogenic	0.64	D
MetaRNN	Pathogenic	0.99	D
MetaSVM	Pathogenic	1.0	D
MutationAssessor	Pathogenic	4.0	H
MutationTaster	Benign	1.0	A;A
PrimateAI	Pathogenic	0.86	D
PROVEAN	Pathogenic	-4.8	D
REVEL	Pathogenic	0.97
Sift	Pathogenic	0.0	D
Sift4G	Uncertain	0.029	D
Polyphen		0.99	D
Vest4		0.98
MutPred		0.96		Loss of MoRF binding (P = 0.0277);
MVP		0.98
MPC		0.99
ClinPred		1.0	D
GERP RS		4.9
Varity_R		0.91
gMVP		0.93

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: rs80338784; hg19: chr17-62036638;