(1997; 132 pages) [French] [Spanish]
Lichen planus is a chronic, papular, pruritic skin eruption that occurs typically in middle age and later life. In some tropical countries, where it affects up to 2% of the population, it may be more common in children and in some instances related to exposure to the sun. Sometimes it is induced by drugs, including chloroquine, streptomycin, amiphenazole, quinidine and gold salts. In most cases, however, there is no obvious cause.
The lesions appear as flat-topped, polygonal, shiny papules, that in light-skinned patients are violet-coloured and, in darker patients, greyish or dark brown. They may occur anywhere, but are commonly found on the flexor surfaces of the wrists, the lumbar region, the genitalia and the lower legs. Older lesions, particularly on the legs, are thickened and may have more scales. Healing, which may not occur for many years, often leaves the skin deeply pigmented. The mucous membranes of the oral cavity may also be involved, and when ulceration occurs, it is important to rule out the possibility of an oral malignancy.
The condition is often mild and may need no treatment or only the use of low-potency topical corticosteroids. Hypertrophic lesions are best treated with topical corticosteroids under occlusive dressings, but treatment with oral corticosteroids such as prednisolone may be needed when large areas of skin or the mucous membranes are involved. Retinoids are also claimed to be useful, but the large doses required are potentially toxic, and the more potent derivatives, such as isotretinoin, tretinoin and etretinate, are proven teratogens.