In the present study, when compared with female WT B6 mice under specific-pathogen-free conditions, all the female BATF–/– mice spontaneously developed ichthyosis-like dermatitis with distinct symptoms such as edema, hyperlinearity, erosions, crusts, scales, and lichenification on their tail skin before 16 weeks of age (Figure 1(a)). The gene discussed is BATF; the disease is ichthyosis.