FLG and Alzheimer disease: This link was strikingly confirmed in 2006 by two landmark studies showing that common, loss-of-function variants in the gene encoding Filaggrin (FLG), the major component of KGs, are the direct cause of the common dry skin condition, ichthyosis vulgaris (IV), and represent the most significant known genetic predisposing factor for atopic dermatitis (AD) [8,9].