What causes pityriasis lichenoides?

Updated: Sep 11, 2020
  • Author: Jeffrey P Callen, MD; Chief Editor: Dirk M Elston, MD  more...
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Answer

The exact etiology of PLC and PLEVA remains elusive; many cases resolve without the discovery of an identifiable culprit. Consideration has been given to the possibility of a low-grade or self-limited lymphoproliferative disorder, a response to an infectious agent, or an inflammatory reaction to an unknown epitope.

A number of acute exanthems (eg, Mucha-Habermann disease, pityriasis rosea, acute lichen planus, guttate psoriasis, erythema multiforme) are believed to be caused by a hypersensitivity reaction to infectious agents. Familial outbreaks, clustering of cases, and comorbid symptoms have been used to support these relationships in Mucha-Habermann disease, although clear causality is lacking. Elevations of pathogen-specific antibody titers also have been offered as proof of causality, but such immunologic responses may represent epiphenomena caused by nonspecific immune responses to unknown pathogens. The most commonly reported associated pathogens are Epstein-Barr virus (EBV), Toxoplasma gondii, and human immunodeficiency virus (HIV).


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