rs1555599644

chr17-80107631-A-AT

Variant summary

Our verdict is Pathogenic. Variant got 18 ACMG points: 18P and 0B. PVS1 PM2 PP5_Very_Strong

The NM_000152.5(GAA):c.768dup(p.Ile257TyrfsTer73) variant causes a frameshift change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. Variant has been reported in ClinVar as Likely pathogenic (★★★). Variant results in nonsense mediated mRNA decay.

• Frequency: Genomes: not found (cov: 34)
• Consequence: GAA NM_000152.5 frameshift
• Clinical Significance: Likely pathogenic reviewed by expert panel P:3
• Conservation: PhyloP100: -0.272

Genes affected

GAA (HGNC:4065): (alpha glucosidase) This gene encodes lysosomal alpha-glucosidase, which is essential for the degradation of glycogen to glucose in lysosomes. The encoded preproprotein is proteolytically processed to generate multiple intermediate forms and the mature form of the enzyme. Defects in this gene are the cause of glycogen storage disease II, also known as Pompe's disease, which is an autosomal recessive disorder with a broad clinical spectrum. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Jan 2016]

ACMG classification

Verdict is Pathogenic. Variant got 18 ACMG points.

• PVS1: Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
• PM2: Very rare variant in population databases, with high coverage
• PP5: Variant 17-80107631-A-AT is Pathogenic according to our data. Variant chr17-80107631-A-AT is described in ClinVar as [Likely_pathogenic]. Clinvar id is 556534.Status of the report is reviewed_by_expert_panel, 3 stars.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	MANE	UniProt
GAA	NM_000152.5	c.768dup	p.Ile257TyrfsTer73	frameshift_variant	4/20	ENST00000302262.8

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	#exon/exons	TSL	MANE	Appris	UniProt
GAA	ENST00000302262.8	c.768dup	p.Ile257TyrfsTer73	frameshift_variant	4/20	1	NM_000152.5	P1

Frequencies

GnomAD3 genomes Cov.: 34

GnomAD4 exome Cov.: 33

GnomAD4 genome Cov.: 34

ClinVar

Significance: Likely pathogenic

Submissions summary: Pathogenic:3

Revision: reviewed by expert panel

Submissions by phenotype

Glycogen storage disease, type II Pathogenic:3

Pathogenic, criteria provided, single submitter	clinical testing	Invitae	Feb 25, 2023	ClinVar contains an entry for this variant (Variation ID: 556534). This sequence change creates a premature translational stop signal (p.Ile257Tyrfs*73) in the GAA gene. It is expected to result in an absent or disrupted protein product. Loss-of-function variants in GAA are known to be pathogenic (PMID: 18425781, 22252923). This variant is not present in population databases (gnomAD no frequency). This premature translational stop signal has been observed in individual(s) with Pompe disease (PMID: 18425781). For these reasons, this variant has been classified as Pathogenic. -
Likely pathogenic, reviewed by expert panel	curation	ClinGen Lysosomal Storage Disorder Variant Curation Expert Panel	Mar 10, 2023	The NM_000152.5:c.768dup (p.Ile257TyrfsTer73) variant in GAA is a frameshift variant predicted to cause a premature stop codon, leading to nonsense mediated decay in a gene in which loss-of-function is an established disease mechanism (PVS1). This variant is not in gnomAD v2.1.1. (PM2_Supporting). The variant has been reported in a patient with Pompe disease but further details regarding the second variant and residual GAA activity are unavailable (PMID: 18425781). There is a ClinVar entry for this variant (Variation ID: 556534). The classification of this variant has been upgraded from Variant of Uncertain Significance to Likely Pathogenic based on the recommendations of the ClinGen Sequence Variant Interpretation Working Group, that a variant meeting PVS1 and PM2_Supporting is classified as Likely Pathogenic (https://clinicalgenome.org/site/assets/files/5182/pm2_-_svi_recommendation_-_approved_sept2020.pdf ). In summary, this variant meets the criteria to be classified as Likely Pathogenic for Pompe disease. GAA-specific ACMG/AMP criteria met, based on the specifications of the ClinGen Lysosomal Diseases VCEP (Specifications Version 2.0): PVS1, PM2_Supporting. (Classification approved by the ClinGen Lysosomal Diseases VCEP, March 10, 2023). -
Likely pathogenic, criteria provided, single submitter	clinical testing	Counsyl	Feb 06, 2018	- -

Computational scores

Source: dbNSFP v4.3

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.070		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: rs1555599644; hg19: chr17-78081430;