First, although we focused on the effect of haptoglobin on the gp91phox as it plays an important role in the pathophysiology of priapism, haptoglobin may have other effects on oxidative stress, such as reducing ROS sources; for example, all the isoforms of NADPH oxidase, unaccompanied eNOS, and xanthine oxidase. Here, FMO5 is linked to Priapism.