LCN2 and infection: The pathogenesis of PAH is closely associated with gene expression, hormones, oxidative stress, infections, and other factors.[7,8] Immunity and inflammation factors affecting leukocytes or mast cells, such as KIT proto-oncogene (KIT), integrin subunit alpha M (ITGAM), C-X-C motif chemokine receptors (CXCRs), and C-C motif chemokine receptors (CCRs), are reported to play a role as well.[23–26,34–36] Lipocalin 2 (LCN2) is another novel molecular marker whose level was recently reported to be increased in the sera of children with PAH.[30,31]