A novel insertion/deletion in APC gene Promotor 1B is associated with both stomach and colon polyposis  

Take home points:  

1. A multi-clinic study following one family with clinical manifestations of both GAPPS and FAP that indicates the genotype-phenotype relationship for APC 1B promoter variants may not be fully characterized.  

2. Pathogenic variants in the APC promoter 1B region are associated with gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS), which has typically been seen as a differential diagnosis from traditional familial adenomatous polyposis (FAP) associated with APC pathogenic variants occurring outside the 1B promoter.