Peutz-Jeghers syndrome is a hereditary affection with dominant autosomal transmission. The risk of cancerisation is largely higher than that in the general population. Dysplasia is rare. Transformation of the polyposis hamartoma into a site of dysplasia then into adenocarcinoma has been rarely reported. The authors report the case of a 14 year-old patient, having a severe dysplasia on ileal polyposis hamartoma related to the syndrome of Peutz-Jeghers.