Use of Biologics in Pityriasis Rubra Pilaris: A Case Report and Review of the Literature

Pityriasis rubra pilaris (PRP) is an inflammatory papulosquamous disorder of unknown etiology. It is characterized by hyperkeratotic scaling plaques with an orange-red hue, “islands of sparing,” and palmoplantar keratoderma; it may cause erythroderma. There have been no completed controlled clinical trials for the treatment of PRP, and there are no FDA approved treatments at this time; most treatment evidence is derived from case reports. This review of the literature explores the use of various biologics which have been attempted for treatment of widespread or treatment resistant PRP. Some case reports have demonstrated efficacy of anti-IL-17 and anti-IL12/23 agents for PRP treatment. IL-17, a pro-inflammatory cytokine, has been found in increased levels in the skin of patients with PRP, and reductions in the level of IL-17 have been correlated with improvement in the histopathologic findings. In this case report and review of the literature, the use of ixekizumab, a humanized IgG4 monoclonal antibody which selectively binds IL-17A and inhibits the IL-17A receptor is explored in the treatment of widespread PRP in a 63 year old woman with treatment resistant erythrodermic PRP. The patient experienced significant resolution of her palmoplantar keratoderma and erythroderma after treament with ixekizumab. Conclusions: Treatment of PRP, particularly treatment resistant PRP, is still in experimental stages. Anti-IL-17 biologics such as ixekizumab and secukinumab show significant promise in the treatment of refractory PRP, as shown by this patient and multiple other case reports. The finding of elevated levels of IL-17 in lesional skin further supports the use of these IL-17 blocking agents