Hamilton MJ, Zhao M, Giannetti MP, et al. - This study was undertaken to investigate if or not intestinal mast cells (MCs) are elevated or have a unique phenotype in individuals with hereditary alpha-tryptasemia (HαT), who have extra copies of the MC tryptase gene TPSAB1 and typically elevated baseline serum tryptase levels >8 ng/mL is not known. Researchers analyzed the duodenal biopsies of 17 patients with HαT and compared them to 15 patients with mast cell activation syndrome who had baseline serum tryptases < 8 ng/mL (MCAS-NT) and 12 GI-controls. They ascertained that the HαT individuals had elevated MCs in the duodenum compared with MCAS-NT and GI-controls. The outcomes reveal that HαT is correlated with elevated small intestinal MCs that may contribute to the prevalent GI manifestations observed among individuals with this genetic trait.