Refractory pityriasis rubra pilaris treated with etanercept, adalimumab, or ustekinumab: A retrospective investigation

Pityriasis rubra pilaris (PRP) is a rare, difficult to treat papulosquamous disorder that responds variably to retinoids and immunosuppression. Successful use of biologics for treating PRP has been described in the literature by case reports and a limited number of case series. To provide additional data, we retrospectively analyzed cases of PRP treated with biologics at our institution. We identified seven patients with a clear diagnosis of PRP treated with adalimumab, etanercept, and/or ustekinumab at our institution from January 1, 2014 to April 1, 2017. Six of seven patients had type I, adult acquired PRP, and one had type V atypical juvenile PRP. In response to tumor necrosis factor (TNF)‐α inhibition, two patients had marked responses (>75% improvement in involved body surface area), while three patients failed to show any improvement on a TNF‐α inhibitor. In two cases of PRP refractory to TNF‐α inhibition, ustekinumab resulted in a partial response (<75% improvement) in one patient and no response in the other. Compared to other published data, our cohort was substantially more resistant to treatment with biologics, a finding which may provide valuable perspective for dermatologists managing refractory PRP in the future.