Amongst others, filament aggregating protein (filaggrin), encoded by the FLG gene, is processed into the cornified envelope, an insoluble network consisting of the debris of keratinocytes—corneocytes—that are tightly crosslinked and imbedded in a matrix of lipid components ultimately forming the physical barrier of the skin: the stratum corneum. Disturbed epidermal differentiation and skin barrier function loss are key hallmarks of common chronic inflammatory skin diseases such as atopic dermatitis (AD) and psoriasis (Pso). This evidence concerns the gene FLG and Alzheimer disease.