A rare inflammatory skin disease with unclear etiology.
It manifests as widespread polymorphic papulosquamous dermatitis that varies in a spectrum of clinical presentations and course. The course of pityriasis lichenoides is unpredictable.
Very rarely, it may progress to the cutaneous form of lymphoma.
It is optimally managed with a combination of topical, light, and systemic therapies.
Pityriasis lichenoides is an uncommon, acquired, idiopathic skin condition. It is a challenging disorder to diagnose, categorize, and treat due to its varied presentation and uncertain course. Pityriasis lichenoides manifests as diffuse polymorphic, papulosquamous dermatitis that varies in severity, temporal onset and development, and prognosis. The scope of presentations is classified along a continuum of 3 subtypes, including pityriasis lichenoides et varioliformis acuta, pityriasis lichenoides chronica, and febrile ulceronecrotic Mucha-Habermann disease.
History and exam
Key diagnostic factors
- acute to subacute recurrent skin eruption
- polymorphic, generalized, nonpruritic skin eruption
Other diagnostic factors
- scars or pigment changes
- recent illness
- family history of pityriasis lichenoides
- multiorgan failure
- childhood to early adult age
- male sex
1st investigations to order
- skin biopsy
Investigations to consider
- antistreptolysin titers
- Epstein-Barr virus IgM/IgG viral capsid antigen and nuclear antigen antibody
- monospot or heterophil antibody test
- hepatitis B surface antigen, antisurface antibody, and anticore IgM
- hepatitis C virus antibody
- HIV screening
- rapid plasma reagin
- throat cultures
- toxoplasma Sabin-Feldman dye test, indirect immunofluorescence/hemagglutination
- erythrocyte sedimentation rate
- serum LDH
- WBC count
- serum albumin
mild to moderate disease
severe disease or treatment resistance
- Lymphomatoid papulosis
- Guttate psoriasis
- Drug eruption
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