A six-year-old girl has been suffering from rashes on the face, chest, and trunk that occur for a week or two, then clear only to recur the next month. The lesions are small macules, vesicles, and crusts that are painful and pruritic. A recent biopsy revealed pityriasis lichenoides et varioliformis acuta (PLEVA). What are the cause and course of this disease? How should it be treated?—Edward F. O’Hara, MD, Dunedin, Fla.

Pityriasis lichenoides is characterized by papulosquamous to papulonecrotic lesional morphology, a chronic and recurrent clinical course, and histopathology demonstrating lichenoid infiltrate with variable dermal hemorrhage and keratinocyte necrosis. Pityriasis lichenoides and its principal variants were identified and reported in a series of articles published in the late 19th and early 20th century. The term pityriasis lichenoides can be used to encompass both acute and chronic presentations, which are characterized by papulosquamous lesions located primarily on the trunk or extremities. These two diseases form a spectrum of a self-limited dermatosis, with the acute type starting as a maculopapular, erythematous eruption that heals with superficial variable scars. The lesions occur in crops over several weeks and may continue for months to years. The papules in PLEVA develop acutely and heal spontaneously with central necrosis; acute episodes are recurrent and persistent. The maculopapular lesions of pityriasis lichenoides chronica (PLC) develop less acutely with an adherent scale and resolve spontaneously with residual pigmentary changes. The etiology of these disorders remains unknown but has been theorized to be a hypersensitivity reaction to infectious agents. The most common treatment options include oral antibiotics, topical steroids, and phototherapy.—Jeffrey M. Weinberg, MD (146-17)

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