A gene-phenotype association, which relates the genotypic differences seen in these patients to the phenotype they display, has been defined, as colorectal polyps are seen in those with either a BMPR1a or SMAD4 DCV, but gastric and upper GI polyps are not commonly seen in those with a BMPR1a DCV [4, 13, 15]. The gene discussed is SMAD4; the disease is polyp of large intestine.