RESUMO
BACKGROUND: One hundred percent of the cases of familial adenomatous polyposis (FAP) will develop carcinoma; therefore, the necessity of diagnosis at an early age with immediate therapy is essential. In the presence of identical twins, it is mandatory for both to undergo comprehensive colonic examination as early as possible. The study took place at a third-level general hospital with the objective of explaining in detail the importance of early diagnosis of FAP. CLINICAL CASES: We report on FAP in identical male twins who were operated on at different times with different outcomes and prognosis. The first twin was treated 20 years previously at an early age and underwent subtotal colectomy with ileoproctostomy. This patient is currently asymptomatic with no evidence of malignancy. The second twin was operated on at the age of 33 years and was already a carrier of a well differentiated rectal adenocarcinoma. CONCLUSIONS: Opportune therapy carried out on the first twin has resulted in a disease-free status, in contrast with the delay in treatment of the second twin who developed carcinoma.