Novel MLH1 nonsense variant in a patient with suspected Lynch syndrome

TL;DR

A new MLH1 gene variant was found in a patient with suspected Lynch syndrome, a hereditary condition that increases cancer risk.

Contribution

The study reports a novel germline MLH1 nonsense variant associated with Lynch syndrome.

Findings

The patient met clinical criteria for Lynch syndrome with high microsatellite instability in tumors.

A novel heterozygous pathogenic MLH1 variant was identified through genetic testing.

Abstract

Loss-of-function germline variants of MLH1 cause Lynch syndrome. Here, we present the case of a 43-year-old male patient diagnosed with cecal and transverse colon adenocarcinomas. The characteristics of the case met the revised Bethesda guidelines, and the tumors demonstrated a high frequency of microsatellite instability. Genetic testing for mismatch repair genes (indicative of Lynch syndrome) revealed a novel heterozygous germline pathogenic variant, NM_000249.4:c.856A>T/NP_000240.1:p.(Lys286Ter), in MLH1.

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