PURPOSE: We report the case of two siblings, clinically and endoscopically followed for 12 years, who displayed an attenuated adenomatous polyposis coli phenotype. METHODS: On workup for rectal bleeding with colonoscopy, we found multiple adenomas mainly right- sided in a 21-year-old female and the same colonic phenotype was observed in her 27-year-old brother. We made a clinical diagnosis of attenuated adenomatous polyposis coli and performed APC gene testing. Because they had refused the proposed ileorectal anastomosis surgical option, we planned a periodic, endoscopic follow- up. RESULTS: Gene testing did not confirm the clinical suspicion of attenuated adenomatous polyposis coli. Actually, we did not find any pathogenic mutation in APC gene and we recently identified a biallelic Y125C MYH defect. During the endoscopic follow- up, a progressive reduction of adenomas was seen. CONCLUSIONS: New insight colorectal cancer genetics have allowed definition of a new class of polyposis that applies to some patients with attenuated adenomatous polyposis coli phenotype as in the siblings we have described. To prevent colorectal cancer without recurring to surgery, colonoscopic polypectomy may be a suitable tool in controlling MYH polyposis.
