Pityriasis Lichenoides

Key Points
Skin condition which may affect various areas of the body
Exact cause is unknown, but may be due to various factors
Classified into acute and chronic forms of the condition
Presentation of symptoms is predicated on the classification of the condition

Pityriasis lichenoides is a skin condition which may affect various areas of the body, and is classified into two distinct forms, Pityriasis lichenoides chronica (PLC) and Pityriasis lichenoides et varioliformis acuta (PLEVA).

PLC presents over the course of up to several months, and initially consists of a small papule which is pink in color. Papules change in color to brownish-red, and may be accompanied by an adherent scale. Papules flatten as the condition progresses and leave a brown discoloration, which fades with time. The condition usually forms on the torso, limbs, and buttocks, but may develop on the hands, feet, scalp and face. The condition may relapse in some cases

PLEVA presents as red patches of skin, which progress into papules which are covered with fine scales. Papules may be filled with blood and/or pus, or may develop a reddish-brown crusting. The condition typically affects the torso and limbs, but can cover widespread areas of skin in any part of the body, and is accompanied by itching and burning in the affected area.

Pityriasis lichenoides typically develops before 30 years of age, and is more common in men. While the cause of the condition is unknown, it may be related to certain infections, t-cell disorders, or a form of hypersensitivity Vasculitis.

Differential Diagnosis (Other conditions with similar appearance)
Chickenpox
Gianotti-Crosti Syndrome
Lichen Planus
Pityriasis rosea
Psoriasis, Guttate

Diagnosis
Key Points
Diagnosis based characteristic appearance of affected area
Other testing may be performed to rule out other conditions

Pityriasis lichenoides is typically diagnosed based on the characteristic appearance of the affected area. Other testing such as laboratory testing or skin biopsy may be performed to rule out similar appearing conditions.

Treatment
Condition is not always responsive to treatment
If rash is asymptomatic, treatment may not be required
Treatment typically consists of topical steroids to relieve itching and irritation and use of topical immunomodulators
Several other therapies may be utilized as a second line of treatment

Pityriasis lichenoides is not always responsive to treatment, and in cases where the attendant rash is asymptomatic, treatment may not be required. In cases where treatment is successful, the condition may recur once treatment is ceased. Treatment typically consists of administration of topical steroids to relieve Itch and irritation and topical immunomodulators such as tacrolimus or pimecrolimus. Additionally, sun exposure and use of oral Antibiotics may be helpful in resolving the condition. Several other therapies may be utilized as a second line of treatment, including phototherapy, systemic steroids, methotrexate, acitretin, dapsone, and ciclosporin. In severe cases, these medications may be given in conjunction with others.