RT Book, Section A1 Schäkel, Knut A2 Kang, Sewon A2 Amagai, Masayuki A2 Bruckner, Anna L. A2 Enk, Alexander H. A2 Margolis, David J. A2 McMichael, Amy J. A2 Orringer, Jeffrey S. SR Print(0) ID 1161323165 T1 Pityriasis Rubra Pilaris T2 Fitzpatrick's Dermatology, 9e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9780071837798 LK dermatology.mhmedical.com/content.aspx?aid=1161323165 RD 2024/03/29 AB AT-A-GLANCEA rare inflammatory papulosquamous dermatosis, often self-limiting within a few years.The disease is subclassified into 6 types, including both hereditary and acquired forms.The hereditary form of pityriasis rubra pilaris is linked to CARD14 gain-of-function mutations, the cause of the acquired forms is unknown.Typical features are follicular hyperkeratotic papules that coalesce into scaly, reddish-orange–colored plaques, which may progress to erythroderma with well-demarcated islands of normal skin.Distinguishing pityriasis rubra pilaris from psoriasis poses a major diagnostic challenge, particularly in the early phases of the disease.Histopathologic examination reveals hyperkeratosis, alternating parakeratosis and orthokeratosis in a checkerboard pattern, with focal acantholytic dyskeratosis.The most successful treatment options are systemic retinoids, methotrexate, and photochemotherapy (psoralen and ultraviolet A). In recent years, biologics blocking tumor necrosis factor-α and interleukins-12 and -12p40 were shown to be effective.