A rare case of Lynch syndrome: the role of genetic testing in diagnosis

Introduction. Lynch syndrome is one of the most common hereditary cancer syndromes, characterized by early-onset development of multiple malignancies, particularly colorectal cancer. It is caused by germline mutations in DNA mismatch repair (MMR) genes. Aim. To present a rare case of Lynch syndrome to familiarize clinicians with current diagnostic approaches. Materials and methods. A clinical case from the authors’ practice is described. Results. The patient, born in 1984, presented with two primary tumors of the colon. Given the early age of onset and multiplicity of tumors, Lynch syndrome was clinically suspected. Molecular genetic testing for microsatellite instability (MSI) was performed, revealing a pathogenic heterozygous germline duplication in the MLH1 gene: NM_000249.4 c.1921dup(p.Leu641Profs*4). The diagnosis was confirmed as Lynch syndrome, and an individualized surveillance program was established. Conclusion. This case illustrates the diagnostic and therapeutic capabilities available for Lynch syndrome and proposes a structured algorithm for long-term follow-up of both diagnosed patients and their at-risk relatives.