Lichen Simplex Chronicus
(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 as well as in patients with any type of underlying chronic dermatitis.
The underlying pathophysiology of lichen simplex chronicus is unknown but may involve alterations in the way the nervous system perceives and processes itchy sensations. Skin that tends toward eczematous conditions (eg, atopic dermatitis) is more prone to lichenification.
Diagnosis of lichen simplex chronicus is by examination. A fully developed plaque is hyperpigmented with varying amounts of erythema that is well-demarcated and has exaggerated skin lines and a thickened and leathery appearance characteristic of lichenification. Look-alike conditions include tinea corporis, lichen planus, and psoriasis; lichen simplex chronicus can be distinguished from these by potassium hydroxide wet mount and biopsy.
Primary treatment of lichen simplex chronicus is patient education about the effects of scratching and rubbing.
Secondary treatment is topical corticosteroids (eg, triamcinolone acetonide, fluocinonide); surgical tape impregnated with flurandrenolide (applied in the morning and replaced in the evening) may be preferred because occlusion prevents scratching. Small areas may be locally infiltrated (intralesional injections) with a long-acting corticosteroid such as triamcinolone acetonide 2.5 mg/mL (diluted with saline), 0.3 mL/cm2 of lesion; treatment can be repeated every 3 to 4 weeks. Oral H1-blocking antihistamines may be useful. Emollients may also be helpful. Topical capsaicin cream may also be helpful, but the initial burning sensations may make this therapy unacceptable to patients.
Chronic scratching 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, and upper trunk and sometimes the anogenital area.
Diagnosis is clinical, but potassium hydroxide wet mount and biopsy can help in the differential diagnosis.
Patients need to be educated about the vicious circle of scratching and further itching; topical corticosteroids and antihistamines help control the itching.