Pityriasis lichenoides

The exact cause of pityriasis lichenoides (PL) remains unknown. Theories on the cause have included the possibility of a low-grade or self-limited lymphoproliferative disorder; a hypersensitive reaction to a bacterial or viral infection; and an inappropriate, inflammatory immune response to an unknown foreign agent. The most commonly reported associated infections in people with PL are Epstein-Barr virus (EBV), Toxoplasma gondii, and human immunodeficiency virus (HIV). Other infections that have been associated with PL include cytomegalovirus, parvovirus (fifth disease), Staphylococcus aureus, and group A beta- haemolytic streptococci. Several therapies, such as chemotherapeutic agents, estrogen-progesterone therapy, the antihistamine astemizole, certain herbs (e.g. kampo), and the measles vaccine have also been linked to the onset of PL. However, no cause-effect relationship between PL and any of these infections or therapies has been proven. PL is not contagious.

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.

Treatment options may include antibiotics, phototherapy, PUVA, or medications that suppress the immune system response (immunosuppressants) in severe cases.

Most cases of pityriasis lichenoides (PL) tend to resolve on their own over time. However, treatment may be used to decrease the duration of the condition, especially if the rash is a nuisance. Initial treatment for PL usually consists of topical or systemic corticosteroids, or oral antibiotics. However, these treatments may cause multiple side effects and are not always effective. Natural sunlight and/or phototherapy treatment may be helpful. A combination of tablets known as Psoralens with UVA (PUVA treatment) may also be helpful, but carries a higher risk of side effects. Severe forms of the disease may be managed by medications that suppress the immune response (immunosuppressants).

Information about specific medications that may be used to treat PL is available on Medscape Reference's website here.