PDE4A and psoriatic arthritis: Apremilast, a small molecule which specifically inhibits the 3′,5′ cyclic adenosine monophosphate (cAMP) specific phosphodiesterase type 4 (PDE4) and modulates the immune system, has been added to the armamentarium for the efficacious treatment of moderate-to-severe plaque Ps, psoriatic arthritis (PsA) and oral ulcers of Behcet’s disease in adults after FDA approval in 2014 [7].