PDE4A and atopic eczema: Crisaborole (AN2728), a nonsteroidal phosphodiesterase 4 (PDE4) inhibitor, represents the first medication approved by the FDA for the treatment of different skin diseases, including atopic dermatitis (AD) and off-label treatment for recalcitrant palmoplantar psoriasis, inflammatory linear verrucous epidermal nevus, seborrheic dermatitis and vitiligo (Makins et al., 2020; Robbins et al., 2018).