rs143177272

Positions:

Variant summary

Our verdict is Pathogenic. Variant got 10 ACMG points: 10P and 0B. PM1PM2PM5PP3_Strong

The NM_005609.4(PYGM):c.2446C>T(p.Arg816Cys) variant causes a missense change involving the alteration of a non-conserved nucleotide. The variant allele was found at a frequency of 0.0000991 in 1,614,036 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 12/21 in silico tools predict a damaging outcome for this variant. Variant has been reported in ClinVar as Uncertain significance (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R816H) has been classified as Pathogenic.

Frequency

Genomes: 𝑓 0.00011 ( 0 hom., cov: 33)

Exomes 𝑓: 0.000099 ( 0 hom. )

Consequence

PYGM
NM_005609.4 missense

Scores

Clinical Significance

Conflicting classifications of pathogenicity criteria provided, conflicting classifications P:1U:4

Conservation

PhyloP100: 3.40

Variant links:

Genes affected

PYGM (HGNC:9726): (glycogen phosphorylase, muscle associated) This gene encodes a muscle enzyme involved in glycogenolysis. Highly similar enzymes encoded by different genes are found in liver and brain. Mutations in this gene are associated with McArdle disease (myophosphorylase deficiency), a glycogen storage disease of muscle. Alternative splicing results in multiple transcript variants.[provided by RefSeq, Sep 2009]

PYGM links:

Genome browser will be placed here

ACMG classification

Classification made for transcript

Verdict is Pathogenic. Variant got 10 ACMG points.

PM1

In a helix (size 10) in uniprot entity PYGM_HUMAN there are 4 pathogenic changes around while only 0 benign (100%) in NM_005609.4

PM2

Very rare variant in population databases, with high coverage;

PM5

Other missense variant is known to change same aminoacid residue: Variant chr11-64746741-C-T is described in Lovd as [Pathogenic].

PP3

MetaRNN computational evidence supports a deleterious effect, 0.971

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	Protein	UniProt
PYGM	NM_005609.4 linkuse as main transcript	c.2446C>T	p.Arg816Cys	missense_variant	20/20	ENST00000164139.4	NP_005600.1
PYGM	NM_001164716.1 linkuse as main transcript	c.2182C>T	p.Arg728Cys	missense_variant	18/18		NP_001158188.1

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Protein	Appris	UniProt
PYGM	ENST00000164139.4 linkuse as main transcript	c.2446C>T	p.Arg816Cys	missense_variant	20/20	1	NM_005609.4	ENSP00000164139	P1	P11217-1
PYGM	ENST00000377432.7 linkuse as main transcript	c.2182C>T	p.Arg728Cys	missense_variant	18/18	2		ENSP00000366650		P11217-2
PYGM	ENST00000483742.1 linkuse as main transcript	n.1799C>T		non_coding_transcript_exon_variant	3/3	2

Frequencies

GnomAD3 genomes

AF:

0.000105

AC:

AN:

152144

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.0000483

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:

0.000206

Gnomad OTH

AF:

0.00

GnomAD3 exomes

AF:

0.0000477

AC:

AN:

251484

Hom.:

AF XY:

0.0000515

AC XY:

AN XY:

135918

show subpopulations

Gnomad AFR exome

AF:

0.00

Gnomad AMR exome

AF:

0.0000289

Gnomad ASJ exome

AF:

0.00

Gnomad EAS exome

AF:

0.0000544

Gnomad SAS exome

AF:

0.00

Gnomad FIN exome

AF:

0.0000924

Gnomad NFE exome

AF:

0.0000703

Gnomad OTH exome

AF:

0.00

GnomAD4 exome

AF:

0.0000985

AC:

144

AN:

1461892

Hom.:

Cov.:

AF XY:

0.000102

AC XY:

AN XY:

727248

show subpopulations

Gnomad4 AFR exome

AF:

0.00

Gnomad4 AMR exome

AF:

0.0000224

Gnomad4 ASJ exome

AF:

0.00

Gnomad4 EAS exome

AF:

0.000101

Gnomad4 SAS exome

AF:

0.0000232

Gnomad4 FIN exome

AF:

0.0000374

Gnomad4 NFE exome

AF:

0.000121

Gnomad4 OTH exome

AF:

0.0000166

GnomAD4 genome

AF:

0.000105

AC:

AN:

152144

Hom.:

Cov.:

AF XY:

0.0000942

AC XY:

AN XY:

74322

show subpopulations

Gnomad4 AFR

AF:

0.0000483

Gnomad4 AMR

AF:

0.00

Gnomad4 ASJ

AF:

0.00

Gnomad4 EAS

AF:

0.00

Gnomad4 SAS

AF:

0.00

Gnomad4 FIN

AF:

0.00

Gnomad4 NFE

AF:

0.000206

Gnomad4 OTH

AF:

0.00

Alfa

AF:

0.000173

Hom.:

Bravo

AF:

0.000117

TwinsUK

AF:

0.00

AC:

ALSPAC

AF:

0.000259

AC:

ESP6500AA

AF:

0.00

AC:

ESP6500EA

AF:

0.000116

AC:

ExAC

AF:

0.00000824

AC:

EpiCase

AF:

0.0000545

EpiControl

AF:

0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Pathogenic:1Uncertain:4

Revision: criteria provided, conflicting classifications

LINK: link

Submissions by phenotype

Glycogen storage disease, type V

Uncertain:2

Uncertain significance, criteria provided, single submitter	clinical testing	Labcorp Genetics (formerly Invitae), Labcorp	Jun 26, 2022	This sequence change replaces arginine, which is basic and polar, with cysteine, which is neutral and slightly polar, at codon 816 of the PYGM protein (p.Arg816Cys). This variant is present in population databases (rs143177272, gnomAD 0.009%). This variant has not been reported in the literature in individuals affected with PYGM-related conditions. ClinVar contains an entry for this variant (Variation ID: 281389). Algorithms developed to predict the effect of missense changes on protein structure and function are either unavailable or do not agree on the potential impact of this missense change (SIFT: "Not Available"; PolyPhen-2: "Probably Damaging"; Align-GVGD: "Not Available"). In summary, the available evidence is currently insufficient to determine the role of this variant in disease. Therefore, it has been classified as a Variant of Uncertain Significance. -
Uncertain significance, criteria provided, single submitter	clinical testing	Fulgent Genetics, Fulgent Genetics	Oct 31, 2018	- -

Tip-toe gait

Pathogenic:1

Likely pathogenic, criteria provided, single submitter

clinical testing

Practice for Gait Abnormalities, David Pomarino, Competency Network Toe Walking c/o Practice Pomarino

Oct 26, 2021

Toe Walking has various causes, ranging from idiopathic or habitual reasons to an underlying neuromuscular disease. The most observed form of toe walking is idiopathic toe walking (ITW) - a diagnosis of exclusion. ITW occurs in about 5% of children after their second birthday and is a common problem in pediatric orthopedics. In about 70% of these cases, there is spontaneous remission within six months of the onset of ITW. If the toe walk persists, one can assume the presence of a non-idiopathic form of toe walk (n-ITW). In n-ITW, the causes of the abnormal gait are neurological or myogenic. Differential diagnoses such as infantile cerebral palsy, muscular dystrophy, spinal amyotrophy and hereditary motor-sensory neuropathy as well as rare metabolic disorders of the musculature must be considered (Pomarino et al., 2018). In our clinical ITW consultation, we screen children with n-ITW for a genetic form of tiptoe gait using next generation sequencing for gene variants in 49 genes. These are genes in which gene variants can lead to neuromuscular diseases in which an association with toe-tapping gait has been reported or can be suspected due to patients’ clinical symptoms. To the best of our knowledge, this is the first study in which several patients with toe walking displayed heterozygosity for pathogenic or likely pathogenic PYGM mutations and mild symptoms of the metabolic muscle disease McArdle. The findings of our research are in line with recently published observations in heterozygous family members patients with McArdle disease. We should mention that some of the patients in our cohort harbored heterozygous variants in other genes of our gene panel. However, the numbers in this study were too small to workout any resulting combined genetic effects. It is concluded that genetic conditions can contribute to the development of toe walking. Apparently, even a slight genetic weakening of the muscles can lead to changes to the gait pattern. Future studies must show how the pathomechanism can be explained for the PYGM variants and whether there are new therapeutic approaches to be developed based on this research. -

Inborn genetic diseases

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Ambry Genetics

Mar 25, 2022

The c.2446C>T (p.R816C) alteration is located in exon 20 (coding exon 20) of the PYGM gene. This alteration results from a C to T substitution at nucleotide position 2446, causing the arginine (R) at amino acid position 816 to be replaced by a cysteine (C). Based on insufficient or conflicting evidence, the clinical significance of this alteration remains unclear. -

not provided

Uncertain:1

Uncertain significance, criteria provided, single submitter

clinical testing

Eurofins Ntd Llc (ga)

Jun 11, 2015

- -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

AlphaMissense

Pathogenic

0.74

BayesDel_addAF

Pathogenic

0.40

BayesDel_noAF

Pathogenic

0.52

CADD

Pathogenic

DANN

Pathogenic

1.0

DEOGEN2

Pathogenic

0.89

.;D

Eigen

Pathogenic

0.72

Eigen_PC

Uncertain

0.56

FATHMM_MKL

Uncertain

0.95

LIST_S2

Pathogenic

1.0

D;D

M_CAP

Pathogenic

0.38

MetaRNN

Pathogenic

0.97

D;D

MetaSVM

Pathogenic

1.0

MutationAssessor

Pathogenic

4.2

.;H

MutationTaster

Benign

1.0

D;D

PrimateAI

Pathogenic

0.83

PROVEAN

Pathogenic

-7.1

D;D

REVEL

Pathogenic

0.96

Sift

Pathogenic

0.0

D;D

Sift4G

Pathogenic

0.0

D;D

Polyphen

1.0

.;D

Vest4

0.91

MVP

0.99

MPC

0.99

ClinPred

1.0

GERP RS

3.5

Varity_R

0.89

gMVP

0.91

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

Below is the list of publications found by LitVar. It may be empty.

Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

LitVar

Other links and lift over