A 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.
Pityriasis rubra pilaris (PRP) is a rare, inflammatory skin disease of juvenile or adult onset with distinctive clinical features and a self-limiting or chronic evolution.
The exact prevalence of PRP is not known. It accounts for approximately 1 in 5000 new patients presenting with skin disease in Great Britain.1 In India this is approximately 1 in 50,000 patients (pityriasis rubra pilaris in Indians.) The disease occurs in all races with an equal male-to-female ratio.2
PRP comprises different entities and most cases are sporadic and have an unknown etiology. Approximately 6.5% of cases of PRP are familial3-5 and linked to CARD14 mutations.6 In 1980, Griffiths proposed classifying PRP into 5 types based on age of onset, clinical course, and prognosis. A sixth, HIV-associated, category was added in later years (Table 29-1).2
Table 29-1Classification Scheme of Pityriasis Rubra Pilarisa ||Download (.pdf) Table 29-1 Classification Scheme of Pityriasis Rubra Pilarisa
|TYPE ||DESCRIPTION ||% OF CASES ||CLINICAL CHARACTERISTICS ||DISTRIBUTION ||COURSE |
|I ||Classic adult ||>50 ||Erythroderma with islands of normal skin (“nappes claires”), follicular hyperkeratosis, waxy diffuse palmoplantar keratoderma ||Generalized, beginning on the head and neck, then spreading caudally ||Often resolves within an average period of 3 years |
|II ||Atypical adult ||5 ||Combination of follicular hyperkeratosis and ichthyosiform lesions on the legs, sparse scalp hair ||Generalized ||Long duration (>20 years) |
|III ||Classic juvenile ||10 ||Similar to type I but appears in years 1 or 2 of life ||Generalized ||Often resolves within an average period of 1–2 years |
|IV ||Circumscribed juvenile ||25 ||Prepubertal children; well-demarcated scaly, erythematous plaques on the elbows and knees, resembling localized psoriasis ||Localized ||Uncertain, some cases clear in the late teens |
|V ||Atypical juvenile, associated with CARD14 mutations ||5 ||Begins in first few years, accounts for most familial cases; follicular hyperkeratosis, scleroderma-like appearance of the hands and feet ||Generalized ||Chronic course, improvement with retinoids but relapses when stopped |
|VI ||HIV-associated ||NAb ||Similar to type ...|