PITYRIASIS RUBRA PILARIS (PRP)

Etiology The etiology is unknown A familial form of the disease exists, with an autosomal dominant inheritance pattern; however, most cases are sporadic One hypothesis is that pityriasis RPR may be related to an abnormal immune response to an antigenic trigger Case reports have described PRP occurring after streptococcal infections

The incidence has been reported to be 1 case in 3500-5000 patients presenting to dermatologic clinics PRP occurs equally among men and women • The familial form typically begins in early childhood • The acquired form has peaks in the first and fifth decades of life, but it can begin at any age

Clinically The familial form of PRP has a gradual onset, whereas the acquired form has an acute onset The disease typically spreads in a craniocaudal (from head to body) direction

PRP is characterized by orange-red or salmon-colored scaly plaques with sharp borders, which may expand to involve the entire body A characteristic feature is presence of islands of unaffected skin within the plaques

The plaques are formed of follicular hyperkeratotic papules

Palmoplantar keratoderma occurs in most patients and tends to have an orange hue Painful fissures may develop in patients with palmoplantar keratoderma

Nail changes include distal yellow-brown discoloration, subungual hyperkeratosis, longitudinal ridging, nail plate thickening, and splinter hemorrhages • Mucous membranes: Patients may complain of pain and irritation in the mouth. Mucous membrane changes include a diffuse whitish appearance of the buccal mucosa, lacy whitish plaques, grayish-white papules and plaques, erythema, or possible erosions

Pruritus, although not a major symptom, may occur in the early stages of the disease

Griffiths classification Course Distrib. C/P Type Often resolves within an average of 3 y Gene-ralized As mentioned before I-Classic adult (>50 of cases) Long duration (> 20 y) Follicular hyper-keratosis and ichthyosiform lesions on the legs, sparse scalp hair II-Atypical adult (5% of cases)

Course Distrib. C/P Type Often resolves within an average of 1-2 y General-ized Similar to type I but appears in year 1 or 2 of life III-Classic juvenile (10 of cases)

Course Distrib. C/P Type Some cases clear in the late teens Locali-zed Prepubertal children; well-demarcated scaly, erythematous plaques on the elbows and knees, resembling localized psoriasis IV- Circu-mscribed juvenile (25% of cases)

Course Distrib. C/P Type Chronic course Gener-alized Begins in first few years, accounts for most familial cases; follicular hyperkeratosis, scleroderma-like appearance of the hands and feet V- Atypical juvenile (5% of cases)

Histopathology Folliculat Plugging: The follicles are filled with dense, horny (keratinous)plugs

There are foci of parakeratosis in the perifo- llicular shoulder and in the epi- dermis between the follicles At other sites, a basket-weave hyper-keratosis overlies a prominent granular layer and there is little parakeratosis

Although the epidermis is acanthotic, it is not, as in psoriasis, thinned above the dermal papillae, and there is no tendency for polymorphs to invade the epidermis There is a dermal infiltrate of lymphocytes and histiocytes

Treatment Currently, oral retinoids are the first line of therapy. Isotretinoin has been reported to be of value, although a comprehensive review suggests that acitretin (0.5 to 0.75 mg/kg per day) may be more effective in clearing lesions. Accordingly, most patients are treated first with acitretin today Therapy with methotrexate(10 to 25 mg weekly, intramuscularly or orally, in divided doses, once a week) has shown variable rates of success

Some cases respond well to photochemotherapy, some may flare, and others require combination treatment with retinoids or methotrexate Several cases of adult-type PRP showed significant clearance in 2 to 4 weeks with cyclosporine(5 mg/kg/day) Although most studies show lack of efficacy Some patients are helped by azathioprine (100 to 150 mg/day) , but this effect is also inconsistent