[Characteristics and clinical analysis of MLH1 c.463dupC gene mutation in a Lynch syndrome family]

In this study, a case of Lynch syndrome (LS) family line with a novel mutation site in the MLH1 c.463dupC gene was reported and the clinical and pathogenic genetic features of this family were analyzed. A 40-year-old female patient with colon cancer diagnosed at the First Affiliated Hospital of Kunming Medical University on October 2, 2020 was retrospectively included. The clinical data of the family were collected and the family lineage was drawn. The family tumor history met the Amsterdam Criteria Ⅱ and the diagnostic criteria of LS in Chinese, which was a typical LS family lineage. A germline code-shift missense mutation c.463dupC in the MLH1 gene located in exon 6, a possible pathogenic variant, was detected by second-generation sequencing (NGS) in the patient. Subsequently, Sanger sequencing was performed on a total of 20 direct lineage members of the family of the MLH1 gene, 7 cases were found to harbor the mutation and included in the LS high-risk control. Follow-up to October 2023 showed that the patient had endometrial and cervical polyps, one case had colorectal cancer, and two cases had intestinal polyps, all were treated with early intervention and therapy; two cases did not show any clinical symptoms. This study is the first to report a new mutation site for the potentially pathogenic MLH1 c.463dupC, providing a rationale for the pathogenicity of the mutation and standardized health management for familial carriers.