However, we believe it is worthwhile to attempt treatment given the published evidence that IL-5/R targeting may benefit a subset of patients with CS-dependent CD3−CD4+ associated HES (5, 12, 35, 39, 40), our observation that angioedema may be attenuated by treatment, the excellent safety profile, and the absence of alternative well-tolerated treatment options. This evidence concerns the gene RRBP1 and Cowden syndrome 1.