PMS2 GENE

PMS2 Gene — Lynch syndrome caused by PMS2 has lower cancer penetrance than MLH1 or MSH2, but the pseudogene PMS2CL makes standard genetic testing unreliable, and WGS provides more accurate evaluation.

Whole genome sequencing evaluates PMS2 with improved accuracy over panel testing by reading through the complex PMS2/PMS2CL pseudogene region — distinguishing true pathogenic variants from pseudogene sequences.

PMS2

About this condition

PMS2 Gene — Lynch Syndrome

PMS2 (chromosome 7p22.1) encodes a DNA mismatch repair protein. Pathogenic PMS2 variants cause Lynch syndrome with lower penetrance than MLH1/MSH2 — approximately 15-20% lifetime CRC risk and 15% endometrial cancer risk (vs. 50-80% CRC for MLH1/MSH2). Despite lower penetrance, PMS2-Lynch still confers clinically significant cancer risk requiring enhanced surveillance.

PMS2 has a unique testing challenge — the pseudogene PMS2CL shares >98% sequence identity with PMS2 exons 1-5, causing variant misassignment in standard next-generation sequencing panels. Variants in the pseudogene may be incorrectly called as PMS2 pathogenic variants (false positives), or true PMS2 variants may be dismissed as pseudogene artifacts (false negatives). Long-range PCR, gene-specific amplification, or whole-genome approaches improve accuracy.

PMS2-Lynch management includes colonoscopy every 1-2 years from age 25-30 (later than MLH1/MSH2 due to lower penetrance), endometrial cancer surveillance for female carriers, and consideration of aspirin chemoprevention. Immunotherapy for PMS2-deficient cancers is highly effective — MSI-high/dMMR tumors respond dramatically to pembrolizumab regardless of which MMR gene is deficient.

PMS2 pseudogene PMS2CL confounds standard genetic testing. Variants are frequently misclassified. If you've had PMS2 'VUS' or 'pathogenic' results from panel testing, WGS confirmation is recommended.

Gene locus: PMS2 (7p22.1)

PMS2 is the hardest Lynch gene to test accurately due to its pseudogene. WGS provides superior evaluation by reading the full genomic context, reducing false positives and negatives from pseudogene interference.

Pseudogene interference causes PMS2 false positives and negatives — WGS resolves the ambiguity

Standard NGS panels frequently misassign variants between PMS2 and PMS2CL. A patient told they have a PMS2 pathogenic variant may actually have a benign pseudogene variant (false positive → unnecessary surveillance). Conversely, a true PMS2 variant may be filtered as pseudogene noise (false negative → missed Lynch diagnosis). WGS reads the full genomic context, improving variant assignment accuracy.

PMS2-Lynch cancers respond to immunotherapy — dMMR status unlocks pembrolizumab regardless of the specific MMR gene

PMS2-deficient tumors are MSI-high and respond to immune checkpoint inhibitors. Pembrolizumab is FDA-approved for all MSI-high/dMMR cancers regardless of tissue of origin. Confirming PMS2 germline status identifies the molecular mechanism underlying MSI-high status and triggers cascade family testing.

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