Three years after MADH4 (also known as SMAD4) was identified as a gene critical to juvenile polyposis, BMPR1A, encoding a receptor in the same pathway, has been identified as another susceptibility gene. The TGFβ/BMP superfamily of molecules has not only been shown to be defective in neoplasia but also in the non-cancer developmental syndromes primary pulmonary hypertension and hereditary hemorrhagic telangiectasia.