This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Pityriasis lichenoides (PL) is a skin condition characterized by small, raised pink spots that tend to come together in groups. It is not contagious. There are two main types of PL: an acute form called pityriasis lichenoides et varioliformis acuta (PLEVA), and a milder, longer-lasting form called pityriasis lichenoides chronica (PLC). There is also a rare, severe variant of PLEVA called febrile ulceronecrotic PLEVA, associated with high fever and complications that may affect other body systems.
In both types of PL, spots usually occur on the trunk, buttox, arms and legs. PLEVA begins abruptly and may cause itching or burning. PLC may develop over days, is less irritating, and lasts longer than PLEVA. Spots associated with PLC typically fade within 3 to 4 weeks, but new spots may then appear. There is no clear consensus regarding how long either form of PL lasts, but most cases resolve on their own within one to several months. Some cases may wax and wane, or relapse over a period of years.
The cause of PL is not known. Theories on the cause have included the possibility of a low-grade or self-limited lymphoproliferative disorder; a reaction to a bacterial or viral infection; and an inappropriate, inflammatory immune response to an unknown foreign agent.
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