SMAD4 and juvenile polyposis syndrome: JPS is caused by pathogenic variants in the BMPR1A gene (chromosome 10q23.2), encoding the bone morphogenetic protein receptor type IA, and in the SMAD4 gene (chromosome 18q21.2), encoding a member of the Smad family of signal transduction proteins, both involved in TGF-β/BMP signaling pathway [170,171].