Pityriasis lichenoides

Definition

Pityriasis lichenoides (PL) is a skin condition characterized by small, raised pink spots that tend to come together in groups.

Cause

• 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.

Types

• 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.

Signs and symptoms

• 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.

Diagnosis

• This condition is diagonised based on clinical history and appearance, and the diagnosis is confirmed by skin biopsy.
• The pathology of PLEVA and PLC are distinct.

Treatment

• 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).

DermNet scaly/pityriasis-lichenoides

NIH genetic and rare disease info

• NIH info on Pityriasis lichenoides

Pityriasis lichenoides is a rare disease.

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