ERAP2 and Crohn disease: Polymorphic variation in the form of single nucleotide variants (SNVs) in the ERAP2 gene has been associated with increased susceptibility to chronic inflammatory disorders, such as Crohn’s disease, birdshot chorioretinopathy, and ankylosing spondylitis, as well as with protection against severe infections such as, pneumonia, as well as the bubonic plague (i.e., The Black Death) in history [2–5].