The “Studded” Rectum: Phenotypic Evidence of MYH-Associated Polyposis

BACKGROUND: MYH-associated polyposis is a recessively inherited syndrome of colorectal cancer predisposition attributed to biallelic germline mutations in the base excision repair gene MYH. Clinically it overlaps with attenuated familial adenomatous polyposis, sporadic oligopolyposis, serrated polyposis, familial colorectal cancer type X, and Lynch syndrome. There is no specific phenotypic feature of MYH-associated polyposis. We have noticed that a proportion of patients with MYH-associated polyposis presenting for yearly colonoscopy surveillance have rectums that are studded with small hyperplastic polyps. OBJECTIVE: We report this as a possible unique phenotypic feature of the syndrome. DESIGN: This was a descriptive study. SETTINGS: The study was conducted at a department of colorectal surgery in a tertiary referral center. PATIENTS: Patients affected with oligopolyposis or MYH-associated polyposis presenting for endoscopic surveillance and polyp control were included. INTERVENTIONS: Interventions included colonoscopy or proctoscopy with excision or biopsy of mucosal lesions. MAIN OUTCOME MEASURES: The presence of rectal studding was measured. RESULTS: There were 49 patients, 16 with biallelic germline mutations of MYH; 10 of these had rectal studding. A sampling of rectal polyps was biopsied and all were hyperplastic. Five patients with biallelic MYH mutations had no studding, and 1 had not been prospectively examined. The studding was independent of the nature of the MYH mutation(s). The 33 patients other patients included 21 with serrated polyposis, 2 with a germline APC mutation, 1 with a PTEN mutation, 2 with mixed polyposis, 3 with oligoadenomatous polyposis and no germline mutation, and 4 patients with oligoadenomatous polyposis who had not been genetically tested. Only 1 of these (oligoadenomatous polyposis, not tested) had studding. LIMITATIONS: The study was limited by its small number of biallelic MYH mutation carriers. CONCLUSIONS: Rectal studding may be a sign of MYH-associated polyposis and raises questions about the biology of abnormal base excision repair.