Pityriasis rubra pilaris - Skin
Pityriasis rubra pilaris (PRP) is characterized by an acute cutaneous eruption that is often accompanied by pruritus and/or pain. Classic cutaneous lesions include follicular papules on an erythematous base coalescing to form large orange-red plaques but with characteristic islands of sparing. PRP commonly begins on the scalp and rapidly spreads in a craniocaudal direction and has the potential to quickly progress to erythroderma over several weeks' time. Additional features include an orange-red palmoplantar keratoderma and sparing of the mucous membranes. PRP can be classified into 5 clinical types based on age of onset, cutaneous features, and clinical course. In classic adult PRP, more than 80% of patients will experience spontaneous remission within 3 years.
The etiology of PRP has not been clearly defined. The onset of disease has been associated with myositis, myasthenia gravis, hypothyroidism, HIV, infection, and malignancy. In addition, UV exposure and minor skin trauma prior to the onset of PRP have been reported. While there are reports of heritable forms, the large majority of PRP cases are acquired and without sex predilection. The incidence of the acquired form occurs in 2 peaks: during the first and second decades and the sixth decade.
For more information, see OMIM.
L44.0 – Pityriasis rubra pilaris
3755001 – Pityriasis rubra pilaris
- Psoriasis – See Diagnostic Pearls.
- Seborrheic dermatitis – Much more responsive to standard therapies. PRP is often resistant to conventional therapies for seborrheic dermatitis. In addition, the progression of body surface involvement will distinguish PRP from seborrheic dermatitis.
- Mycosis fungoides / Sezary syndrome – Generalized lymphadenopathy, circulating malignant lymphocytes as determined by flow cytometry, leonine facies, a CD4/CD8 ratio greater than 10 as determined by flow cytometry.
- Erythrokeratoderma variabilis – More than 90% of patients present within the first year of life.
- Drug eruption – Often present with urticarial, exanthematous, or vesicular / bullous lesions. In addition, systemic symptoms are more pronounced, including fever, lymphadenopathy, and facial edema. Eosinophilia on CBC and histology are often seen (but not an invariable finding). Medication history will help.
- Atopic dermatitis – Patients are often aware of their atopic history, and the condition commonly starts in childhood. Look for lichenified plaques on the flexural surfaces and neck.
- Erythrokeratodermia variabilis