CASP14 and Alzheimer disease: Filaggrin and caspase‐14, a filaggrin‐cleaving enzyme, are reduced in AD.7, 8, 9 In addition, attenuated expression of claudin‐1, a tight junction protein, has been identified histologically.10, 11 Furthermore, decreased claudin‐1 promotes AD‐like skin inflammation in a mouse model.12