Pityriasis rubra pilaris
Overview
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.
Symptoms
PRP most often starts as a patchy rash on the scalp, face or chest. The rash has an orange-red color ("salmon") and the palms and soles become thickened. Rough, dry plugs can be felt within the rash. Thick skin on the palms and soles can split and become painful. Walking may be sore. The itching is usually severe at first, and then later is not as bad as you would think considering how bad the rash looks.
Causes
The cause of pityriasis rubra pilaris is not known. It is not an infection and cannot be passed on to others. Pityriasis rubra pilaris mostly affects adults over 40, but some children are also affected. Sometimes minor burns rashes and infections seem to trigger it. There is no blood test for PRP. It is usually diagnosed when a dermatologist, suspecting the condition, does a biopsy and specifically asks it to be checked for PRP. Sometimes Pityriasis rubra pilaris is suspected only after the usual creams, pills and even ultraviolet light treatments used for skin conditions have no effect.
Treatment
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. Topical medications such as emollients may be used to relieve symptoms of dryness and cracking. In severe cases acitretin or isotretinoin may be useful. Methotrexate has been of limited value