Other rare colonic polyposis syndromes for which the genetic basis is known include Cowden syndrome (mutations in PTEN), juvenile polyposis (mutations in SMAD4 or BMPR1A), hereditary mixed polyposis syndrome (mutation in GREM1), and MUTYH-associated polyposis (biallelic mutations in MUTYH). The gene discussed is GREM1; the disease is hereditary mixed polyposis syndrome.