BMPR1A and juvenile polyposis syndrome: Case reports have shown that in BMPR1A families with polyposis phenotypes, polyps of both serrated and adenomatous lineages are present [28], Juvenile polyps dominate the gastrointestinal phenotype in SMAD4 mutation carriers, however, a deleterious frameshift mutation in SMAD4 has been described in a case of juvenile polyposis previously classified as SPS, where multiple serrated polyps were also present [19].