Gardner's syndrome is an autosomal dominant disease caused by a mutation in the APC gene with 20-30% of cases presenting de novo. This entity is a variant of familial adenomatous polyposis, with a prevalence of 3/100,000 habitants. It may present as early as 2 months of age with a variety of both colonic and extracolonic symptoms. We report a case of a 21-year-old man, without any known family history, presenting with microcytic hypochromic anemia and constitutional symptoms for two months. Ultimately, after the etiological study, Gardner syndrome diagnosis was established as an index primary familiar case. Gardner syndrome is a clinical challenge which requires a prompt suspicion in order to reach its diagnosis. Given the malignant evolution of adenomas in 100% of untreated patients, early identification of extraintestinal manifestations (identifiable prior to colonic symptoms) is of the essence. A consequent endoscopic study to confirm gastrointestinal involvement is essential for a more favorable prognosis.