SMAD2 and Alzheimer disease: A study by Xinhui Ni's team revealed that KCs with specific deletion of RNA deconjugating enzyme DDX5 were more prone to skin inflammation including AD, and that the cytokine IL‐17D could regulate skin inflammation such as AD by suppressing DDX5 expression in KCs through activation of the CD93–p38 MAPK–AKT–SMAD2/3 signaling pathway.79