chr18-62157747-G-A

Variant names:

• chr18-62157747-G-A
• rs558341655
• NM_176787.5:c.283C>T

Variant summary

Our verdict is Pathogenic. The variant received 14 ACMG points: 14P and 0B. PM2 PM5 PP3_Moderate PP5_Very_Strong

The NM_176787.5(PIGN):​c.283C>T​(p.Arg95Trp) variant causes a missense change. The variant allele was found at a frequency of 0.0000192 in 1,460,066 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. Variant has been reported in ClinVar as Likely pathogenic (★★). Another variant affecting the same amino acid position, but resulting in a different missense (i.e. R95Q) has been classified as Likely pathogenic.

• Frequency:
  • Genomes: not found (cov: 33)
  • Exomes 𝑓: 0.000019 (0 hom.)
• Consequence: PIGN NM_176787.5 missense
• Clinical Significance: Pathogenic/Likely pathogenic criteria provided, multiple submitters, no conflicts P:7
• Conservation: PhyloP100: 4.96
• Publications: 3 publications found

Genes affected

PIGN (HGNC:8967): (phosphatidylinositol glycan anchor biosynthesis class N) This gene encodes a protein that is involved in glycosylphosphatidylinositol (GPI)-anchor biosynthesis. The GPI-anchor is a glycolipid found on many blood cells and serves to anchor proteins to the cell surface. This protein is expressed in the endoplasmic reticulum and transfers phosphoethanolamine (EtNP) to the first mannose of the GPI anchor. Two alternatively spliced variants, which encode an identical isoform, have been reported. [provided by RefSeq, Jul 2008]

PIGN Gene-Disease associations (from GenCC):

• multiple congenital anomalies-hypotonia-seizures syndrome 1

  Inheritance: AR Classification: DEFINITIVE, STRONG, MODERATE, SUPPORTIVE Submitted by: Labcorp Genetics (formerly Invitae), Ambry Genetics, G2P, Orphanet, ClinGen, PanelApp Australia
• Fryns syndrome

  Inheritance: AR Classification: SUPPORTIVE Submitted by: Orphanet

ACMG classification

Our verdict: Pathogenic. The variant received 14 ACMG points.

• PM2: Very rare variant in population databases, with high coverage
• PM5: Other missense variant is known to change same aminoacid residue: Variant chr18-62157746-C-T is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 648403.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.
• PP3: MetaRNN computational evidence supports a deleterious effect, 0.928
• PP5: Variant 18-62157747-G-A is Pathogenic according to our data. Variant chr18-62157747-G-A is described in ClinVar as Pathogenic/Likely_pathogenic. ClinVar VariationId is 378361.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

Variant Effect in Transcripts

ACMG analysis was done for transcript: NM_176787.5. You can select a different transcript below to see updated ACMG assignments.

RefSeq Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	PIGN	NM_176787.5	MANE Select	c.283C>T	p.Arg95Trp	missense	Exon 5 of 31	NP_789744.1
	PIGN	NM_001438896.1		c.283C>T	p.Arg95Trp	missense	Exon 5 of 32	NP_001425825.1
	PIGN	NM_012327.6		c.283C>T	p.Arg95Trp	missense	Exon 4 of 30	NP_036459.1

Ensembl Transcripts

Selected	Gene	Transcript	Tags	HGVSc	HGVSp	Effect	Exon Rank	Protein	UniProt
	PIGN	ENST00000640252.2	TSL:1 MANE Select	c.283C>T	p.Arg95Trp	missense	Exon 5 of 31	ENSP00000492233.1
	PIGN	ENST00000400334.7	TSL:1	c.283C>T	p.Arg95Trp	missense	Exon 4 of 30	ENSP00000383188.2
	PIGN	ENST00000638424.1	TSL:5	n.283C>T		non_coding_transcript_exon	Exon 3 of 29	ENSP00000491963.1

Frequencies

GnomAD3 genomes Cov.: 33

GnomAD2 exomes AF: 0.00 AC: 0 AN: 246712 AF XY: 0.00

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: 0.00

Gnomad OTH exome AF: 0.00

GnomAD4 exome AF: 0.0000192 AC: 28 AN: 1460066 Hom.: 0 Cov.: 30 AF XY: 0.0000151 AC XY: 11 AN XY: 726192

African (AFR) AF: 0.0000299 AC: 1 AN: 33466

American (AMR) AF: 0.00 AC: 0 AN: 44598

Ashkenazi Jewish (ASJ) AF: 0.00 AC: 0 AN: 26098

East Asian (EAS) AF: 0.00 AC: 0 AN: 39658

South Asian (SAS) AF: 0.0000116 AC: 1 AN: 85890

European-Finnish (FIN) AF: 0.00 AC: 0 AN: 53362

Middle Eastern (MID) AF: 0.00 AC: 0 AN: 5766

European-Non Finnish (NFE) AF: 0.0000234 AC: 26 AN: 1110908

Other (OTH) AF: 0.00 AC: 0 AN: 60320

GnomAD4 genome Cov.: 33

Alfa AF: 0.0000387 Hom.: 0

Bravo AF: 0.0000113

Asia WGS AF: 0.000289 AC: 1 AN: 3478

ClinVar

Significance: Pathogenic/Likely pathogenic

Submissions summary: Pathogenic:7

Revision: criteria provided, multiple submitters, no conflicts

Submissions by phenotype

Multiple congenital anomalies-hypotonia-seizures syndrome 1 Pathogenic:4

Jul 31, 2023

3billion

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The variant is not observed in the gnomAD v2.1.1 dataset. Predicted Consequence/Location: Protein truncation variants are a common disease-causing mechanism. In silico tool predictions suggest damaging effect of the variant on gene or gene product (REVEL: 0.79; 3Cnet: 0.96). Same nucleotide change resulting in same amino acid change has been previously reported to be associated with PIGN related disorder (PMID: 26633542). A different missense change at the same codon (p.Arg95Gln) has been reported as pathogenic/likely pathogenic with strong evidence (ClinVar ID: VCV000648403 /PMID: 29096607 /3billion dataset). Therefore, this variant is classified as Likely pathogenic according to the recommendation of ACMG/AMP guideline.

Jan 23, 2020

Baylor Genetics

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was determined to be likely pathogenic according to ACMG Guidelines, 2015 [PMID:25741868].

May 04, 2022

Mendelics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

May 04, 2024

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Likely pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This sequence change replaces arginine, which is basic and polar, with tryptophan, which is neutral and slightly polar, at codon 95 of the PIGN protein (p.Arg95Trp). This variant is not present in population databases (gnomAD no frequency). This missense change has been observed in individual(s) with an abnormality of the nervous system and/or PIGN-related conditions (PMID: 26633542, 35179230, 35468813). In at least one individual the data is consistent with being in trans (on the opposite chromosome) from a pathogenic variant. ClinVar contains an entry for this variant (Variation ID: 378361). 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 PIGN protein function with a positive predictive value of 80%. 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.

not provided Pathogenic:2

Sep 23, 2025

GeneDx

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); In silico analysis supports that this missense variant has a deleterious effect on protein structure/function; This variant is associated with the following publications: (PMID: 26633542, 35468813, 36322149, 33528536, 38456468, 35179230)

Oct 04, 2017

Center for Pediatric Genomic Medicine, Children's Mercy Hospital and Clinics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Inborn genetic diseases Pathogenic:1

Mar 25, 2025

Ambry Genetics

Significance: Pathogenic

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The c.283C>T (p.R95W) alteration is located in exon 5 (coding exon 2) of the PIGN gene. This alteration results from a C to T substitution at nucleotide position 283, causing the arginine (R) at amino acid position 95 to be replaced by a tryptophan (W). This variant was not reported in population-based cohorts in the Genome Aggregation Database (gnomAD). This variant has been identified in the homozygous state and/or in conjunction with other PIGN variant(s) in individual(s) with features consistent with PIGN-related glycosylphosphatidylinositol deficiency; in at least one instance, the variants were identified in trans (Bayat, 2022; Tian, 2022; Loong, 2023). Other variant(s) at the same codon, c.284G>A (p.R259Q), have been identified in individual(s) with features consistent with PIGN-related glycosylphosphatidylinositol deficiency (Thiffault, 2017; Jalkh, 2019, Duval, 2021). This amino acid position is highly conserved in available vertebrate species. This alteration is predicted to be deleterious by in silico analysis. Based on the available evidence, this alteration is classified as pathogenic.

Computational scores

Source: dbNSFP v4.9

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Pathogenic	0.98
BayesDel_addAF	Pathogenic	0.39	D
BayesDel_noAF	Pathogenic	0.32
CADD	Pathogenic	30
DANN	Pathogenic	1.0
DEOGEN2	Benign	0.39	T
Eigen	Pathogenic	0.74
Eigen_PC	Uncertain	0.65
FATHMM_MKL	Uncertain	0.94	D
LIST_S2	Pathogenic	1.0	D
M_CAP	Uncertain	0.11	D
MetaRNN	Pathogenic	0.93	D
MetaSVM	Uncertain	0.38	D
MutationAssessor	Pathogenic	3.7	H
PhyloP100		5.0
PrimateAI	Pathogenic	0.80	T
PROVEAN	Pathogenic	-7.5	D
REVEL	Pathogenic	0.79
Sift	Pathogenic	0.0	D
Sift4G	Pathogenic	0.0	D
Polyphen		1.0	D
Vest4		0.95
MVP		0.89
MPC		0.20
ClinPred		1.0	D
GERP RS		4.5
Varity_R		0.82
gMVP		0.96
Mutation Taster		=1/99	disease causing (ClinVar)

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.010		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Other links and lift over

dbSNP: rs558341655; hg19: chr18-59824980; COSMIC: COSV62952342; COSMIC: COSV62952342;