The pathogenesis behind HMPS stems from a large duplication just upstream of the Grem1 gene, resulting in Grem1 overexpression, and the development of polyps of mixed morphologies from a young age.81 At elevated levels, Grem1 has been linked to tumour progression and risk of metastatic dissemination in several types of cancers.79,82 Therapeutic targeting of Grem1 may prove to be a pivotal therapeutic avenue that can alter the fate of cancer driven by the BMP pathway, though future studies are needed to elucidate this.83 This evidence concerns the gene GREM1 and hereditary mixed polyposis syndrome.