A novel germline SMAD4 variant detected in a Japanese family with juvenile polyposis syndrome and hereditary hemorrhagic telangiectasia

Jpn J Clin Oncol. 2023 Mar 7;53(3):275-279. doi: 10.1093/jjco/hyac189.


Juvenile polyposis syndrome (JPS) is an autosomal dominant, inherited disorder caused by pathogenic germline variants of mainly SMAD4 or BMPR1A genes. Some patients with JPS, especially with SMAD4 variants, also develop hereditary, hemorrhagic telangiectasia (HHT). HHT is also an autosomal dominant inherited disorder. Herein, we identified a novel germline pathogenic variant of the SMAD4 in a Japanese family with JPS and HHT. A six-base pair deletion in the SMAD4 gene (NM_005359.6:c.1495_1500delTGCATA) was identified in the patients. Two amino acids are deleted from SMAD4 protein (p.Cys499_Ile500del), which are located in MSH2 domain essential for the binding with SMAD3. This is a novel variant that has not been registered in any database surveyed. Amino acid structural analysis predicted significant changes in the secondary and three-dimensional structures in the vicinity of the two amino acids' deletion. The variant is classified as 'Likely Pathogenic' according to the American College of Medical Genetics and Genomics guidelines.

Keywords: SMAD4 gene; hereditary hemorrhagic telangiectasia; juvenile polyposis syndrome.

MeSH terms

  • East Asian People
  • Germ Cells
  • Humans
  • Intestinal Polyposis* / complications
  • Intestinal Polyposis* / genetics
  • Neoplastic Syndromes, Hereditary* / complications
  • Neoplastic Syndromes, Hereditary* / genetics
  • Smad4 Protein / genetics
  • Telangiectasia, Hereditary Hemorrhagic* / complications
  • Telangiectasia, Hereditary Hemorrhagic* / genetics


  • Smad4 Protein
  • SMAD4 protein, human

Supplementary concepts

  • Juvenile polyposis syndrome