Devergie disease, lichen acuminatus, and lichen psoriasis are some of the synonyms used to refer to pityriasis rubra pilaris (PRP). It is a group of rare, chronic disorders that is chiefly characterized by an itchy, severely flaky, orange-red scaly rash with thickening of the skin on the hands and feet and some involvement of the nails.
The PRP rash may involve just the knees and elbows or it may cover a wider surface area of the body. While some children may be affected, the condition usually has a bimodal distribution with peak incidences in the first decade and in the fifth decades of life.
The specific pathogenetic mechanisms that give rise to PRP are still unknown. There are studies that suggest it may be genetically acquired, while there are countless others that claim it is actually sporadic. Factors associated with the acquisition of the disease via the latter route involve metabolic abnormalities with the processing of vitamin A in the body. There have been some indications that PRP may also arise due to infections and rashes associated with burns. Another suspected trigger is stress and the condition, regardless of the cause implicated, is not suspected until therapies used for closely related conditions have failed.
Classifications and related conditions
Devergie disease can be classified into five main types on the basis of clinical features, age of disease onset, and the prognosis. A sixth subtype is also considered and is an HIV-associated PRP. Type I PRP is the classical, most common presentation in adults, which manifests as follicular hyperkeratosis and progressive erythroderma (also known as exfoliative dermatitis) with an orange hue on the soles and palms and yellow-brown discoloration of the nails. Type II is an atypical adult onset PRP associated with eczematous skin changes and hair loss. Type III is classical juvenile PRP and usually occurs before the fifth birthday, while type IV is a more localized form of juvenile PRP with lesions primarily on the elbows, knees, and other bony prominences on the body. Type V is an atypical juvenile onset PRP with proposed familial linkages.
PRP is commonly mistaken for psoriasis, which presents more frequently in the population and is characterized by a dry, well-circumscribed, silver-gray rash that may manifest as papules (small pimples) or plaques (raised patches of skin). The psoriatic rash may be found on the scalp and buttocks and, like PRP, on the elbows and knees as well. Another closely related condition to PRP is lichen planus. Lichen planus is characterized by a recurrent itchy rash of inflammatory, small angular spots on the skin and is accompanied by lesions inside the mouth. As is the case with PRP, the exact cause of lichen planus is unknown. Pityriasis rosea is yet another condition related to PRP and is a mild and self-limited disease, presenting as an inflammatory scaly rash found predominantly on the trunk. It is thought to occur due to an unidentified infectious agent.
Management and Treatment
There are many treatment options available, albeit without much success, since it is difficult to treat diseases like PRP that have an unknown etiology. Treatments used for the condition include oral vitamin A supplements, which are limited due to their toxic effects on the body when used in large doses. However, synthetic vitamin A therapy has been employed to circumvent this problem. Other treatment options include the use of steroids and other immunosuppressive and cytotoxic pharmaceuticals.