The field of human microbiome research has undergone a revolution in its approach toward understanding how microorganisms influence the physiology of their host 1. The influence of the oral microbiota is not confined to this location 2. Periodontitis is a "chronic inflammatory disease associated with dysbiotic plaque biofilms and characterized by a progressive destruction of the tooth supporting apparatus"3. Given these observations, the central research question of the present study is to determine the prevalence of periodontitis in patients with Lynch syndrome (LS) compared with reference prevalence estimates from the general population40.

Inclusion Criteria:

1. Age ≥18 years;
2. All sexes eligible
3. Established diagnosis of LS performed as part of clinical practice, with a germline pathogenic/likely pathogenic variant in one of the following genes: MLH1, MSH2, MSH6, PMS2, and EpCAM
4. LS subjects undergoing surveillance gastrointestinal endoscopy according to clinical practice and international guidelines.
5. Subjects underwent dental and periodontal examination

Exclusion Criteria:

1. Age < 18 years;
2. Absence of sufficient periodontal clinical or radiographic data to establish a periodontal diagnosis;
3. Subjects affected by systemic, autoimmune, chronic inflammatory, neurological, or severe psychiatric disorders, or by any other clinical condition that may interfere with study participation or data interpretation
4. Subjects with systemic conditions known to strongly affect periodontal status (e.g. uncontrolled diabetes, autoimmune inflammatory diseases, ongoing cancer therapy) were excluded to reduce major confounding factors that could independently alter periodontal outcomes.

All the subjects affected by LS, treated between the established study period, will be considered enrolled in the present study, as long as they meet the inclusion criteria. Patients will be anonymized by specific procedures explained in the following paragraphs. All records identifying the subject must be kept confidential and, to the extent permitted by the applicable laws and/or regulations, not be made publicly available.

Subjects with Lynch Syndrome (LS) will be identified and recruited through the Gastroenterology and Gastrointestinal Endoscopy Unit, where LS patients are routinely followed within dedicated surveillance programs.

A subset of these patients has also undergone dental and periodontal evaluation at the Dentistry Unit of IRCCS Ospedale San Raffaele as part of routine clinical care, independent from the present study.