A rare inflammatory skin disease with unclear aetiology.
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, categorise, 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's disease.
History and exam
Key diagnostic factors
- acute to subacute recurrent skin eruption
- polymorphic, generalised, non-pruritic skin eruption
Other diagnostic factors
- scars or pigment changes
- recent illness
- family history of pityriasis lichenoides
- multi-organ failure
- childhood to early adult age
- male sex
1st investigations to order
- skin biopsy
Investigations to consider
- anti-streptolysin titres
- Epstein-Barr virus IgM/IgG viral capsid antigen and nuclear antigen antibody
- monospot or heterophil antibody test
- hepatitis B surface antigen, anti-surface antibody, and anti-core IgM
- hepatitis C virus antibody
- HIV screening
- rapid plasma reagin
- throat cultures
- toxoplasma Sabin-Feldman's dye test, indirect immunofluorescence/haemagglutination
- erythrocyte sedimentation rate
- serum LDH
- WBC count
- serum albumin
mild to moderate disease
severe disease or treatment resistance
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