Genotype-phenotype correlations in carriers of the PMS2 founder variant c.1831dup.

Mol Genet Genomic Med

Institute for Medical Genetics and Pathology, University Hospital Basel, Basel, Switzerland.

Published: January 2024

Background: Lynch syndrome represents one of the most common cancer predispositions worldwide and is caused by germline pathogenic variants (PV) in DNA mismatch repair (MMR) genes. We repeatedly identified a PV in the MMR gene PMS2, c.1831dup, accounting for 27% of all Swiss PMS2 PV index patients identified. Notably, 2/18 index patients had been diagnosed with colorectal cancer (CRC) before age 30.

Methods: In this study, we investigated if this PV could (i) represent a founder variant by haplotype analysis and (ii) be associated with a more severe clinical phenotype.

Results: Haplotype analysis identified a shared common region of about 0.7 Mb/1.3 cM in 13 (81%) out of 16 index patients. Genotype-phenotype correlations, combining data from the 18 Swiss and 18 literature-derived PMS2 c.1831dup PV index patients and comparing them to 43 Swiss index patients carrying other PMS2 PVs, indicate that the PMS2 c.1831dup variant may be associated with earlier (<50 y) age at CRC diagnosis (55% vs. 29%, respectively; p = 0.047). Notably, 30% (9/30) of cancers from c.1831dup carriers displayed atypical MMR protein expression patterns on immunohistochemistry.

Conclusion: Our results suggest that the PMS2 c.1831dup PV represents a, probably ancient, founder mutation and is possibly associated with an earlier CRC diagnosis compared to other PMS2 PVs.

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Source
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC10797823PMC
http://dx.doi.org/10.1002/mgg3.2360DOI Listing

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