PDE4A and inflammatory skin disease: Furthermore, PDE4 isoforms are overexpressed in epidermal skin biopsies of patients with atopic dermatitis, and apremilast significantly reduces inflammation and remodeling of atopic epidermis in vitro and in animal models of atopic dermatitis, suggesting an anti-inflammatory role of PDE4 inhibitors in inflammatory skin diseases by targeting keratinocytes (Schafer et al. 2019).