For instance, KIT (CD117) is a gene encoding proto-oncogene c-kit, which is a transmembrane receptor for mast cell growth factor, and it may participate in vascular remodeling in PAH.[34–36] In addition, CPA3 encodes a member of the carboxypeptidase A family of zinc metalloproteases and preproprotein which is released by mast cells, and may be involved in the degradation of endogenous proteins in PAH.[37] Taken together, these results suggest that the mast cells may play a crucial role in male PAH. This evidence concerns the gene KIT and pulmonary arterial hypertension.