The first is autosomal dominant familial adenomatous polyposis (FAP, OMIM #175100), which is caused by heterozygous germline variants in the tumour-suppressor gene and Wnt signalling pathway regulator APC [3, 4].The second is autosomal recessive MUTYH-associated polyposis (MAP, OMIM #608456), which is caused by biallelic germline variants in the base-excision-repair gene MUTYH [5]. Here, APC is linked to neoplasm.