Our verdict is Pathogenic. The variant received 10 ACMG points: 10P and 0B. PVS1PP5_Moderate
The NM_000251.3(MSH2):c.367-525_493del(p.Ala123fs) variant causes a frameshift, splice acceptor, splice region, intron change involving the alteration of a non-conserved nucleotide. The variant was absent in control chromosomes in GnomAD project. It is difficult to determine the true allele frequency of this variant because it is of type DEL_BIG, and the frequency of such variant types in population databases may be underestimated and unreliable. Variant has been reported in ClinVar as Pathogenic (★). Synonymous variant affecting the same amino acid position (i.e. A123A) has been classified as Likely benign. Variant results in nonsense mediated mRNA decay.
MSH2 (HGNC:7325): (mutS homolog 2) This locus is frequently mutated in hereditary nonpolyposis colon cancer (HNPCC). When cloned, it was discovered to be a human homolog of the E. coli mismatch repair gene mutS, consistent with the characteristic alterations in microsatellite sequences (RER+ phenotype) found in HNPCC. Two transcript variants encoding different isoforms have been found for this gene. [provided by RefSeq, Apr 2012]
MSH2 Gene-Disease associations (from GenCC):
Lynch syndrome
Inheritance: AD Classification: DEFINITIVE, SUPPORTIVE Submitted by: G2P, ClinGen, Orphanet
Lynch syndrome 1
Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), Genomics England PanelApp, Ambry Genetics
Muir-Torre syndrome
Inheritance: AD Classification: DEFINITIVE, STRONG, SUPPORTIVE Submitted by: Genomics England PanelApp, Orphanet, G2P
mismatch repair cancer syndrome 1
Inheritance: AR Classification: DEFINITIVE, SUPPORTIVE Submitted by: ClinGen, Orphanet
Our verdict: Pathogenic. The variant received 10 ACMG points.
PVS1
Loss of function variant, product undergoes nonsense mediated mRNA decay. LoF is a known mechanism of disease.
PP5
Variant 2-47409567-TTGGCCAGGACGGTCTCGATCTCCTGACCTCGTGATCCGCCTGCCTTGGCCTCCCAAAGTGTTGGGATTACAGGCGTGAGCCACAGCACTCAGCCAGTTATTTTTTTATAAGAAAACATTTTACTGGCCAGGCCTGGTGGCTCACACCTGTAATCCCAGCACTTTGGGAGGCCGAGGCAGGCGGATCACGAGGTCAGGAGTTCGAGACCAGCCTGGCCAACATGGTGAAACCCCATCTCTACTAAAAATACAAAAATTAGCCAGGCGTGGTGGTGTGCGCCTGTATTCCCAGCTACTGGGGAGGCTGAAGCAGGAGAATCGATTGAACCCTTGAGGCAGAGGTTGCAGTGAGTTGAGATCGCACCATTGCACTCTAGCCTGGGTGACAGAGCAAGACTTCATCTCAAAAAAAAGAGAAAACATTTTATTAATAAGGTTCATAGAGTTTGGATTTTTCCTTTTTGCTTATAAAATTTTAAAGTATGTTCAAGAGTTTGTTAAATTTTTAAAATTTTATTTTTACTTAGGCTTCTCCTGGCAATCTCTCTCAGTTTGAAGACATTCTCTTTGGTAACAATGATATGTCAGCTTCCATTGGTGTTGTGGGTGTTAAAATGTCCGCAGTTGATGGCCAGAGACAGGTTGGAGTTGGG-T is Pathogenic according to our data. Variant chr2-47409567-TTGGCCAGGACGGTCTCGATCTCCTGACCTCGTGATCCGCCTGCCTTGGCCTCCCAAAGTGTTGGGATTACAGGCGTGAGCCACAGCACTCAGCCAGTTATTTTTTTATAAGAAAACATTTTACTGGCCAGGCCTGGTGGCTCACACCTGTAATCCCAGCACTTTGGGAGGCCGAGGCAGGCGGATCACGAGGTCAGGAGTTCGAGACCAGCCTGGCCAACATGGTGAAACCCCATCTCTACTAAAAATACAAAAATTAGCCAGGCGTGGTGGTGTGCGCCTGTATTCCCAGCTACTGGGGAGGCTGAAGCAGGAGAATCGATTGAACCCTTGAGGCAGAGGTTGCAGTGAGTTGAGATCGCACCATTGCACTCTAGCCTGGGTGACAGAGCAAGACTTCATCTCAAAAAAAAGAGAAAACATTTTATTAATAAGGTTCATAGAGTTTGGATTTTTCCTTTTTGCTTATAAAATTTTAAAGTATGTTCAAGAGTTTGTTAAATTTTTAAAATTTTATTTTTACTTAGGCTTCTCCTGGCAATCTCTCTCAGTTTGAAGACATTCTCTTTGGTAACAATGATATGTCAGCTTCCATTGGTGTTGTGGGTGTTAAAATGTCCGCAGTTGATGGCCAGAGACAGGTTGGAGTTGGG-T is described in ClinVar as Pathogenic. ClinVar VariationId is 525792.Status of the report is criteria_provided_single_submitter, 1 stars.
This variant is a gross deletion of the genomic region encompassing part of exon 3 of the MSH2 gene, including the  intron 2-exon 3 boundary (c.367-525_493del). This likely creates a premature translational stop signal and is expected to result in an absent or disrupted protein product. This variant has not been reported in the literature in individuals with MSH2-related disease. Loss-of-function variants in MSH2 are known to be pathogenic (PMID: 15849733, 24362816). For these reasons, this variant has been classified as Pathogenic. -