Updated December 30, 2014.

Pityriasis rubra pilaris (PRP), like psoriasis, is a skin disease caused by problems with keratinization -- the scientific term for the normal growth and maturation of skin cells. Psoriasis and PRP rashes look so similar that sometimes a skin biopsy is needed to tell them apart.

What Causes PRP?

The exact cause is unknown and since PRP is much rarer than psoriasis, there has been less research done on the disease.

Similarities and Differences Between PRP and Psoriasis

Both diseases:

• can cause thickening, reddening and scaliness of the palms and soles
• can cause red skin plaques on other areas of the body
• can affect fingernails and toenails
• may lead to the Koebner response where an injury to the skin can produce the rash itself.

Differences: PRP causes the presence of distinct follicular-based papules. In other words, there are small hard plugs in every skin follicle, versus the more scaly appearance of psoriasis.

Treatment of PRP

PRP may get better just by doing simple things like using moisturizers or keratolytics. It can also be treated with phototherapy, methotrexate and retinoid drugs like Soriatane. In many cases, RPR goes away completely over time.

_{Reference: Paller A, Mancini A. Hurwitz Clinical Pediatric Dermatology. Elsevier Saunders, 2006}