PDE4A and Alzheimer disease: Phosphodiesterases are indicated as inducers of PS and AD inflammatory disorders (Smith et al., 2004; Schafer, 2012; Schafer et al., 2014), with PDE4 being specifically identified as induced in keratinocytes and infiltrated leukocytes of PS, and AD lesions (Oger et al., 2005; Schafer et al., 2014).