mismatch repair deficiency
Loss of cellular DNA repair function that increases mutation rates and predicts immunotherapy response.
Full Definition
Mismatch repair deficiency (MMRd) occurs when cells lose the ability to correct DNA replication errors, resulting in increased mutation burden and characteristic molecular signatures. This condition can arise from inherited mutations in MMR genes (Lynch syndrome) or somatic inactivation through promoter methylation. MMRd tumors exhibit increased neoantigen production, making them highly responsive to immune checkpoint inhibitors. Testing for MMRd status through immunohistochemistry or molecular methods is now standard practice in colorectal and endometrial cancer management.
Usage
Usage note: Hyphenate compound term; abbreviate as MMRd only after first use.
In Context
- "Immunohistochemistry revealed mismatch repair deficiency with loss of MLH1 and PMS2 expression." — Pathology report
- "Patients with mismatch repair deficiency showed exceptional response to pembrolizumab therapy." — Clinical research manuscript