[Diagnosis and treatment of lichen planus].

Lichen planus is a chronic, inflammatory, autoimmune disease that affects the skin, oral mucosa, genital mucosa, scalp, and nails. Lichen planus lesions are described using the six P's (planar [flat-topped], purple, polygonal, pruritic, papules, plaques). Onset is usually acute, affecting the flexor surfaces of the wrists, forearms, and legs. The lesions are often covered by lacy, reticular, white lines known as Wickham striae. Classic cases of lichen planus may be diagnosed clinically, but a 4-mm punch biopsy is often helpful and is required for more atypical cases. High-potency topical corticosteroids are first-line therapy for all forms of lichen planus, including cutaneous, genital, and mucosal erosive lesions. In addition to clobetasol, topical tacrolimus appears to be an effective treatment for vulvovaginal lichen planus. Topical corticosteroids are also first-line therapy for mucosal erosive lichen planus. Systemic corticosteroids should be considered for severe, widespread lichen planus involving oral, cutaneous, or genital sites. Referral to a dermatologist for systemic therapy with acitretin (an expensive and toxic oral retinoid) or an oral immunosuppressant should be considered for patients with severe lichen planus that does not respond to topical treatment. Lichen planus may resolve spontaneously within one to two years, although recurrences are common. However, lichen planus on mucous membranes may be more persistent and resistant to treatment.