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Lichen simplex chronicus is a skin disorder that results from chronic scratching. It may represent the final or end stage of cutaneous conditions that cause severe and chronic itching or pruritus, such as atopic dermatitis. This skin disorder usually manifests as thickened skin with increased prominence of normal skin markings, caused by long-term rubbing or scratching. Treatment involves breaking the itch-scratch cycle and administering medications that control the inflammation and itching.
Also known as circumscribed neurodermatitis or neurodermatitis circumscripta, lichen simplex chronicus predominantly affects adults of ages 30 to 50 years. When this condition occurs as nodules, it is called prurigo nodularis. Lichen simplex chronicus has no sex predilection. People who have atopic dermatitis, however, often suffer from this condition at an earlier age compared to non-atopic people.
Lichen simplex chronicus typically manifests as severe itching with roughening of the skin. Itching becomes worse in the presence of heat, sweating, irritation from clothing, and psychological distress. Lichen simplex chronicus earned its name because its appearance resembles that of lichen on a tree. The typical skin lesions are erythematous, or red, raised, and with scales. Although its pathogenesis is not fully established, it is postulated that chronically repetitive trauma caused by rubbing or scratching induces a hyperplastic cutaneous response.
Upon microscopic examination, the rete ridges manifest elongation, and the papillary dermis contains fibrosis and lymphocytes. Marked epidermal thickening, or acanthosis, increased production of keratin, or hyperkeratosis, and hypergranulosis occur. Of interest is the fact that the microscopic lesions of lichen simplex chronicus are similar to the normal skin of the palms and soles, but unlike the palms and soles, the lesions of lichen simplex chronicus have dermal scarring. Common areas of involvement include the dorsum of the feet, ankles, posterior neck, and scalp. Women may experience this condition on the labia majora, and men may experience it on the scrotum.
Treatment of lichen simplex chronicus involves the application of high-potency topical glucocorticoids with occlusion, such as betamethasone dipropionate or clobetasol dipropionate. Among patients who have intractable disease, glucocorticoid injection on the actual lesions may be needed. To control the pruritus and prevent scratching, oral antihistamines such as hydroxyzine or tricyclic antidepressants with intrinsic antihistamine activity, such as doxepin, may be given. These antihistaminic drugs usually lead to sedation or sleepiness, thus persons who are taking them should avoid activities that require full alertness, such as driving or operating heavy equipment. Adjunct drugs, such as emollients, are used to prevent dryness, which may aggravate itching.