mismatch repair deficiency
Also written as: dMMR — deficient mismatch repair
A cellular defect in DNA repair mechanisms that leads to increased mutation rates in tumors.
Full Definition
Mismatch repair deficiency (dMMR) occurs when cells lose the ability to correct errors that arise during DNA replication, leading to the accumulation of mutations throughout the genome. This deficiency can result from germline mutations in mismatch repair genes (causing Lynch syndrome) or from somatic inactivation of these genes in tumors. Tumors with mismatch repair deficiency typically exhibit high microsatellite instability and increased neoantigen burden, making them highly responsive to immune checkpoint inhibitors. Testing for MMR deficiency has become standard practice in colorectal and endometrial cancers to guide treatment decisions.
Usage
Usage note: Can be abbreviated as dMMR (deficient) or MMR deficiency. Distinguish from pMMR (proficient).
In Context
- "Immunohistochemistry confirmed mismatch repair deficiency in the tumor specimen." — Pathology report
- "Patients with dMMR tumors showed higher response rates to pembrolizumab." — Clinical trial manuscript