For example, it is known that 30–50% of AD patients have a loss-of-function mutation in the filaggrin gene (FLG); a mutation of the SPINK 5 (serine peptidase inhibitor Kazal-type 5) gene, encoding for antiprotease LEKTI (lympho-epithelial Kazal-type-related inhibitor), and associated with the initial phase of AD. Here, FLG is linked to Alzheimer disease.