Attenuated adenomatous polyposis with MSH6 variation: Two case reports

Rationale: Adenomatous polyposis (AP) is a genetic disorder characterized by the occurrence of numerous adenomatous polyps in the colon and rectum and can be classified into classical AP and attenuated AP (AAP). AAP is diagnosed when the number of observed adenomas is between 10 and 99. The detection of AAP is significantly increasing mainly due to the improvement of the imaging technique and application of the screening program for colorectal cancer detection. Currently, the germline variations of the APC and MUTYH genes are reported as the main cause of classical AP. However, the underlying genetic basis of AAP is not well understood. In this study, we report 2 cases of AAP with MSH6 variations. Patient concerns: Both patients visited the hospital after multiple polyps were detected during colonoscopies conducted as part of their health checkups. Diagnoses: The 2 patients were diagnosed with AAP through colonoscopic examination at our hospital. Interventions: The 2 received genetic consultation; and, for follow-up purposes, both patients agreed to be tested for an underlying genetic condition through next generation sequencing. And germline MSH6 variations were detected in both AAP patients. Outcomes: There was no recurrence for both patients for 3 years follow-up. Lessons: Minor portion of AAP can cause by genetic mutation in MSH6, and further research is needed.