PDE4A and asthma: New PDE4 inhibitors are the focus of intensive drug discovery, not least because recent genome-wide studies indicate that PDE4 may be involved in the pathogenesis of stroke (Nilsson-Ardnor et al., 2005, Staton et al., 2006), bone density (Reneland et al., 2005), and asthma (Hansen et al., 2000, Himes et al., 2009).