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Lichen simplex, or circumscribed neurodermatitis, is an eczematous eruption that is created by habitual scratching of a single localized area. The disease is more common in adults, but may be seen in children. The areas most commonly affected are those that are conveniently reached. Patients derive great pleasure in the relief that comes with frantically scratching the inflamed site. Loss of this pleasurable sensation or continued subconscious habitual scratching may explain why this eruption frequently recurs in lichen simplex.
A typical plaque stays localized and shows little tendency to enlarge with time. Red papules coalesce to form a red, scaly, thick plaque with accentuation of skin lines (lichenification). Lichen simplex is a chronic eczematous disease, but acute changes may result from sensitization with topical medication. Moist scale, serum, crust, and pustules are signs.
Lichen simplex nuchae occurs almost exclusively in women who reach for the back of the neck during stressful situations. The disease may spread beyond the initial well-defined plaque. Diffuse dry or moist scale, crust, and erosions extend into the posterior scalp beyond the neck. Secondary infection is common. Nodules, usually less than 1 cm and scattered randomly in the scalp, occur in patients who frequently pick.
The patient must first understand that the rash will not clear until even minor scratching and rubbing is stopped. Scratching frequently takes place during sleep, and the affected area may have to be covered. Lichen simplex is chronic eczema and is treated as outlined.
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LICHEN SIMPLEX CHRONICUS: AREAS MOST COMMONLY AFFECTED LISTED IN APPROXIMATE ORDER OF FREQUENCY
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Treatment of the anal area or the fold behind the ear does not require potent topical steroids as do other forms of lichen simplex; rather, these intertriginous areas.
Lichen simplex nuchae, because of its location, is difficult to treat. Dry inflammation that extends into the scalp may be treated with a group II steroid gel such as fluocinonide (Lidex).
Moist, secondarily infected areas respond to oral antibiotics and topical steroid lotions. A 2- to 3-week course of prednisone (20 mg twice daily) should be considered when an extensively inflamed scalp does not respond rapidly to topical treatment. Nodules caused by picking at the scalp may be very resistant to treatment, requiring monthly intralesional injections.