A Case of Pityriasis Rubra Pilaris Treated Successfully with the Phosphodiesterase-4 Inhibitor Apremilast.

Pityriasis rubra pilaris (PRP) is an inflammatory skin condition characterized by well-circumscribed hyperkeratotic plaques and palmoplantar keratoderma (1). The aetiology of PRP is unclear and although various treatment options, such as topical steroids and oral retinoic acids, are available, treatment responses are inconsistent and management is often difficult (2). We report here a case of PRP that was treated successfully with apremilast, a phosphodiesterase-4 (PDE4) inhibitor. Furthermore, using immunohistochemistry we examined the expression of nuclear factor of kappa light chain enhancer in B cells (NF-κB) and caspase recruitment domain family, member 14 (CARD14), a molecule that induces activation of NF-κB and is reported to be involved in the pathogenesis of PRP in the skin.