FLG and Alzheimer disease: Further well-examined SBF-related factors in AD are filaggrin loss-of-function-mutations because of the important structural function of filaggrin in HS and its role in producing components of the natural moisturising factor (NMF) (especially at superficial SC depth), with consequential impact on the physiologic hydration, (acidic) pH and SP activity regulation, and the antimicrobial properties of the SC [4,16].