Lichen planus

Definition:

A disorder of the skin and the mucous membranes resulting in inflammation, itching, and distinctive skin lesions.

Causes, incidence, and risk factors:

Lichen planus is a rare disorder involving a recurrent, itchy, inflammatory rash or lesion on the skin or in the mouth. The exact cause is unknown, but the disorder is likely to be related to an allergic or immune reaction. The HLA A-3 cell marker is associated with lichen planus.

The disorder has been known to develop after exposure to potential allergens such as medications, dyes, and other chemical substances. Symptoms are increased with emotional stress, possibly because of changes in immune system functioning during stress.

Lichen planus generally occurs at or after middle age. It is very rare in the pediatric population. The initial attack may last for weeks to months, resolve, then recur for years.

Lichen planus has been associated with disorders such as bullous pemphigoid, alopecia areata, vitiligo, chronic ulcerative colitis, hypogammaglobulinemia, or graft-vs.-host reaction, and other disorders with immune response components.

Chemicals or medications associated with development of lichen planus include gold (used to treat rheumatoid arthritis), antibiotics, arsenic, iodides, chloroquine, quinacrine, quinidine, antimony, phenothiazines, diuretics such as chlorothiazide, and many others.