The development of atopic dermatitis is linked to loss-of-function mutations in the skin barrier genes SPINK5, a serine protease inhibitor, FLG (filaggrin), which crosslinks keratin fibers in keratinocytes (11) and Tmem79 (mattrin), a transmembrane protein involved in stratum corneum barrier function (12). The gene discussed is FLG; the disease is atopic eczema.