Pityriasis Rubra Pilaris

Description

• Pityriasis rubra pilaris (PRP) is a rare papulosquamous inflammatory skin condition characterized by red-orange scaly plaques, palmoplantar keratoderma, and follicular keratotic papules. In adults, lesions typically begin on the scalp, spreading to other areas of the body in a craniocaudal direction, and leaving characteristic islands of spared normal skin (“nappes claires”). PRP may progress to generalized erythroderma.
• Divided into subtypes by Griffith classification (1): See “Physical Exam” section for descriptions.
  • Type I: classic adult
  • Type II: atypical adult
  • Type III: classic juvenile
  • Type IV: circumscribed juvenile
  • Type V: atypical juvenile
  • Type VI: HIV-associated PRP
• In classic adult PRP, >80% of patients experience spontaneous resolution within 3 years. However, atypical adult and juvenile forms are chronic and intractable (2)[C].
• Pediatric considerations: Lesions typically begin on the lower half of the body as opposed to adult presentations and may resemble seborrheic dermatitis. The 3-year remission rate is 32% (2)[C].

Epidemiology

• Predominant age: bimodal distribution; most cases occur in the 1st and then the 5th to 7th decades of life, with the 6th to 7th being the most common decades for presentation (2)[C].
• No gender predominance

Incidence

• 1/400,000 patients
• 1/3,500 to 5,000 patients presenting to dermatology clinics

Etiology and Pathophysiology

• Unknown
• Hypothesis that type III may be related to an abnormal immune response to an antigenic trigger
• IL-23–TH17 axis has been implicated as a pathogenic inflammatory pathway.
• Tumor necrosis factor (TNF) mRNA is elevated in PRP lesions similar to the level found in psoriasis, explaining the recent rise and potential value of anti-TNF agents in therapy (3).
• Case reports also document this rash in postinfection states, including after streptococcal infections.
• Some studies show that abnormal vitamin A metabolism and/or vitamin A deficiency may play some role in PRP etiology. However, others have not found any association.

Genetics
Familial occurrence has been described.

• Familial type is most often autosomal dominant, but recessive forms have also been described.
• Familial type associated with CARD14 mutation

General Prevention

No known preventive measures

Commonly Associated Conditions

• Hypothyroidism
• Seronegative arthritis
• Myositis
• Myasthenia gravis
• Hypothyroidism
• Celiac sprue
• Infections, including HIV
• Other autoimmune diseases
• Malignancies