(See also Definition of Dermatitis.)
Lichen simplex chronicus is thickened and leathery (lichenified) skin with variable scaling that arises secondary to repetitive scratching or rubbing. Lichen simplex chronicus is not a primary process. Perceived pruritus in a specific area of skin (with or without underlying pathology) provokes rubbing and mechanical trauma, resulting in secondary lichenification and further pruritus. Lichen simplex chronicus frequently occurs in people with anxiety disorders and nonspecific emotional stress. Patients with atopy or atopic dermatitis are particularly susceptible, given their predisposition to itch. Lichen simplex chronicus of the scrotum or vulva is often caused by an itch signal initiated by sacral sensory neuron radiculopathy.
Starting with an initial itch signal (for which the reason is sometimes unclear), the patient reacts by repeatedly scratching and/or rubbing the skin. The underlying pathophysiology of lichen simplex chronicus is unknown but may involve alterations in the way the nervous system perceives and processes itchy sensations.
Lichen simplex chronicus is characterized by pruritic, dry, scaling, hyperpigmented, lichenified plaques (single or multiple) in irregular, oval, or angular shapes. It involves easily reached sites, most commonly the legs, arms, neck, upper trunk, and genital region. It does not occur in areas of the skin that the patient cannot reach, such as the mid back (unless patient uses a back-scratching tool).
Prurigo nodularis is a related condition, likely a more prominent manifestation. In this disorder, skin lesions (nodules) are thicker and typically multiple.
Diagnosis of lichen simplex chronicus is by examination. A fully developed plaque is often hyperpigmented with varying amounts of erythema that is well-demarcated and has exaggerated skin lines and a thickened and leathery appearance characteristic of lichenification.
Lichen planus is a main differential diagnosis, and a biopsy is sometimes needed to differentiate between the two.
If a cause of the initial itch can be identified (eg, radiculopathy, ill-fitting shoes, atopy), it should be treated or addressed. Otherwise, the primary treatment of lichen simplex chronicus is patient education about the effects of scratching and rubbing.
Secondary treatment is topical corticosteroids. Thick, well-established lesions usually require a high-potency topical corticosteroid (eg, clobetasol ointment). Efficacy can be further increased by using the topical corticosteroid under occlusion, for example, by covering the treated area with plastic wrap and leaving it on overnight. There are also commercial products available in which a topical corticosteroid (eg, flurandrenolide) is integrated into an occlusive adhesive tape. Small areas may be locally injected with a long-acting corticosteroid such as a crystal suspension of triamcinolone acetonide 5 to 10 mg/mL; treatment can be repeated every 3 to 4 weeks.
Oral H1-blocking antihistamines, emollients, and topical capsaicin cream may also be helpful.
Starting with an initial itch, chronic scratching and/or rubbing causes further itching, creating a vicious circle.
Itchy, dry, scaling, hyperpigmented, lichenified plaques occur in irregular, oval, or angular shapes on the legs, arms, neck, upper trunk, and the genital area.
Diagnosis is clinical; a biopsy is rarely needed.
The cause of the initial itch, if identifiable, must be addressed.
Patients need to be educated about the vicious circle of scratching/rubbing and avoid doing so repeatedly; topical corticosteroids and antihistamines help control the itching.