CLDN1 and Alzheimer disease: Strikingly, the commonly significant downregulation of CLDN-1 expression level was found in the epidermis of patients with AD (Figure 2A), in bronchial epithelium of patients with AA (Figure 2B), and in esophageal epithelium of patients with EoE (Figure 2C), suggesting that claudin-1 expression level is commonly downregulated in epithelial cells of patients with allergic diseases of the skin, airways, and GI tract.