Genes encoding for protease inhibitors such as the gene "serine peptidase inhibitor, Kazal type 5" (SPINK5) are important to prevent excessive protease activity resulting in skin barrier defects (Hansson et al. 2002; Denecker et al. 2008), and polymorphisms in this gene have been shown to be associated with human AD (Walley et al. 2001; Nishio et al. 2003; Weidinger et al. 2008). Here, SPINK5 is linked to Alzheimer disease.