Pityriasis Rubra Pilaris
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- 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].
- 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
- 1/400,000 patients
- 1/3,500 to 5,000 patients presenting to dermatology clinics
Etiology and Pathophysiology
- 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.
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
No known preventive measures
Commonly Associated Conditions
- Seronegative arthritis
- Myasthenia gravis
- Celiac sprue
- Infections, including HIV
- Other autoimmune diseases