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AT-A-GLANCE

AT-A-GLANCE

  • 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.

EPIDEMIOLOGY

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

CLINICAL FEATURES

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

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