Pityriasis rubra pilaris
What is pityriasis rubra pilaris?
Pityriasis rubra pilaris (PRP) is the name given to a group of rare skin disorders that present with reddish-orange coloured scaling patches with well defined borders. They may cover the entire body or just parts of the body such as the elbows and knees, palms and soles.
Often there are areas of uninvolved skin, particularly on the trunk and limbs, which are referred to as
islands of sparing.
The palms and soles are usually involved and become diffusely thickened and yellowish (palmoplantar keratoderma). PRP is often initially mistaken for another skin condition, usually psoriasis.
Why does it occur and who is at risk?
The cause of PRP is unknown. PRP is usually sporadic but in some forms it may be partially inherited. It may occur in any race, and males and females are equally affected.
There are several forms of PRP that are classified as follows:
|Classical adult onset||
|Atypical adult onset||
|Classical juvenile onset||
|Atypical juvenile onset||
What does it look like?
Classical adult-onset PRP most often starts on the head, neck and upper trunk as a red scaly rash. Often there is a solitary lesion but within a few weeks multiple patches appear and they join together to form groups of reddish-orange lesions. Over a few weeks these spread downwards and may cover most of the body (erythroderma). Rough, dry plugs can be felt within the patches and are due to plugged hair follicles, often most obvious on the backs of the fingers. Patients may also complain of itching in the early stages of the disease.
The palms and soles become thickened and yellow coloured. Cracks may develop which can be painful and make walking and using the hands difficult. The nails may become thickened and discoloured at the free nail edge and may show linear black streaks (splinter haemorrhages). The hair may thin considerably.
What treatments are available?
The value of treatment is difficult to assess, as the clinical course is so variable for each of the different types of PRP. In general, the inherited forms of PRP tend to persist throughout life whilst the sporadically acquired forms tend to resolve spontaneously eventually.
Book: Textbook of Dermatology. Ed Rook A, Wilkinson DS, Ebling FJB, Champion RH, Burton JL. Fourth edition. Blackwell Scientific Publications.
On DermNet NZ:
- PRP Alliance
- PRP Support group
- Pityriasis Rubra Pilaris – Medscape Reference
- Pityriasis Rubra Pilaris – British Association of Dermatologists