Thus, NOX enzymes, the major superoxide-producing enzymes in sickle RBCs, endothelial cells, and leukocytes, are a potentially noteworthy source of ROS in SCD and they are likely critical in triggering the SCD-related inflammatory state, especially the absolute implication of soluble circulating xanthine oxidase (XO) and endothelial-associated XO in ROS generation in the vasculature is still unclear. Here, XDH is linked to Schnyder corneal dystrophy.