Pityriasis lichenoides is an erythematous, papulosquamous, T-cell–mediated dermatosis.1 Both acute and chronic forms are described and represent the extremes of a continuous spectrum.1 Pityriasis lichenoides et varioliformis acuta (PLEVA) refers to the acute form.
It is a common disorder. It occurs most often during the second and third decades of life.2 There is a slight male predominance.2
An immunologically mediated reaction to an infectious agent is suspected to be the cause because sporadic outbreaks are common, and the disease has been reported to occur simultaneously among family members.2 An infection-mediated cause is also suggested by reports of PLEVA following infection with specific pathogens, by the isolation of specific pathogens coincidental with the disease, and by the presence of elevated serum titers to specific pathogens.2 Epstein-Barr virus, parvovirus, human immunodeficiency virus, group A β-hemolytic streptococci, and Toxoplasma gondii are the organisms most frequently reported in association with PLEVA.3- 5
Monoclonal T-cell receptor gene rearrangements and predominance of CD8+ T cells in the infiltrates have been described in patients with PLEVA.1,5 The dominant T-cell clone might represent a host-immune response to an infectious agent.
Pityriasis lichenoides et varioliformis acuta is characterized by the rapid onset of numerous reddish-brown macules and papules that usually evolve into vesicles, pustules, and crusted ulcers. The lesions have a polymorphous appearance, erupt in crops, and are distributed mainly on the trunk and extremities. The face, scalp, mucous membranes, palms, and soles are usually spared. Constitutional symptoms are uncommon. Lesions are usually asymptomatic and resolve in a few weeks to a few months. Rarely, there may be associated fever, malaise, headache, or pruritus.
Pityriasis lichenoides et varioliformis acuta might be complicated by secondary bacterial superinfection of the lesions, residual scars, or postinflammatory hypopigmentation or hyperpigmentation.
The epidermal changes include intercellular and intracellular edema, parakeratosis, and exocytosis of lymphocytes and erythrocytes.6 Dermal changes include a diffuse infiltrate, predominantly lymphocytic, which is more pronounced in the perivascular regions.6
The diagnosis of PLEVA is based on the distinctive clinical appearance. Histological confirmation is rarely necessary. The differential diagnosis includes pityriasis rosea, guttate psoriasis, Gianotti-Crosti syndrome, leukocytoclastic vasculitis, lymphomatoid papulosis, varicella, secondary syphilis, drug eruption, and insect bites.
No treatment is necessary for mild and asymptomatic cases. For symptomatic cases, erythromycin in combination with natural sunlight is the recommended treatment. Erythromycin is prescribed for the anti-inflammatory action rather than for the antibiotic effect. Phototherapy with UV-A, UV-B, or psoralen–UV-A should be considered for symptomatic cases that persist notwithstanding treatment with erythromycin.
Correspondence: Alexander K. C. Leung, MD, Suite 200, 233 16th Ave NW, Calgary, Alberta, Canada T2M 0H5 (email@example.com).
Accepted for Publication: May 31, 2005.
Picture of the Month—Diagnosis. Arch Pediatr Adolesc Med. 2005;159(10):978-979. doi:10.1001/archpedi.159.10.979