The epidermal differentiation process is affected by the disease-specific cytokine milieu (the Th2-cytokines in AD (e.g., IL-4) or the Th1/Th17 cytokines in Pso), or due to genetic predisposition mostly associated to AD (e.g., FLG loss-of-function mutations [1,2], FLG copy number variation [3], hornerin (HRNR)- Single-Nucleotide Polymorphism (SNP) [4,5], small proline-rich protein 3 (SPRR3) [6]. Here, HRNR is linked to Alzheimer disease.