This study evaluated the differential impact of SMAD4 and BMPR1A gene mutations on cancer risk and oncological phenotype in patients with juvenile polyposis syndrome.
Genetic analysis of the CDC73 gene [for Hyperparathyroidism-jaw tumor (HPT-JT)], MEN1 for Multiple Endocrine Neoplasia Type1, CDKN1B for MEN4, SDHB and SDHD for Paraganglioma/Pheochromocytoma susceptibility, VHL for von Hippel-Lindau Syndrome, BMPR1A and SMAD4 for Juvenile Polyposis Syndrome (JPS) (sequencing and MLPA), karyotype and array CGH (44 K) were all normal.
Patients with gastric juvenile polyposis and SMAD4 mutations are at a high risk of developing gastric cancer; hence, early gastrectomy should be considered.
Here we show that conditional inactivation of Bmpr1a in mice disturbs homeostasis of intestinal epithelial regeneration with an expansion of the stem and progenitor cell populations, eventually leading to intestinal polyposis resembling human juvenile polyposis syndrome.
Juvenile polyposis (JP) and hereditary hemorrhagic telangiectasia (HHT) are clinically distinct diseases caused by mutations in SMAD4 and BMPR1A (for JP) and endoglin and ALK1 (for HHT).
Loss-of-function pathogenic variants in SMAD4 cause juvenile polyposis syndrome and we hypothesize that the gain-of-function pathogenic variants observed in Myhre syndrome may contribute to neoplasia in the patients reported herein.
If no causative ENG or ACVRL1 mutation is found, proband samples are referred for sequence analysis of MADH4 (associated with a combined syndrome of juvenile polyposis and HHT).
The genetic variations can alter the structure and function of the BMPR1A gene that causes several diseases such as juvenile polyposis syndrome or hereditary cancer-predisposing syndrome.
The SMAD4 and BMPR1A genes that are involved in 50-60% of JPS cases have not been investigated in the ~ 20 published cases of NF1-associated JLIHMPs with the exception of the abovementioned patient with concomitant JPS and NF1.
Due to the chromosome 10 deletion involving contiguous portions of BMPR1A and PTEN in our patient, he may be at risk for CS associated cancers and features, in addition to the polyps associated with JPS.
We reason that, even in the absence of juvenile polyposis syndrome, sequencing and copy number analysis of BMPR1A should be considered in patients with (atrioventricular) septal defects, especially when associated with facial dysmorphism and anomalous growth.
Pathogenic germline mutations in both the SMAD4 and BMPR1A genes involved in the transforming growth factor beta pathway account for 40% of cases of JPS.