CASE #1: Lichen simplex chronicus (lichen nuchae)
The diagnosis was lichen simplex chronicus (LSC), a secondary reactive process that results from scratching or rubbing and manifests clinically as increased skin markings and thickness (a visual mimic of tree bark or lichens on a stone). In the presence of a primary dermatosis, increase in skin markings and thickness is sometimes deemed secondary lichenification.
Not all patients who rub or scratch manifest with LSC. Asians appear more susceptible. It is uncertain if this proclivity of Asians is due to the manner in which they rub their skin or the manner in which their skin reacts to rubbing. Women manifest LSC more commonly than men. Lichen nuchae is a form of lichen simplex that occurs on the midposterior neck and is observed almost exclusively in women. LSC manifests most commonly in middle-aged rather than elderly patients, who have the highest incidence of xerotic skin. In one study, 12% of aging patients with pruritic skin had LSC.
LSC manifests as an individual demarcated plaque usually with increased skin markings and thickening. The skin can be darkened, i.e., hyperpigmented or brown, and may have a texture resembling a sheet of pebbles or leather. The plaques can be scaly or contain erosions. LSC can affect any body area on either side, independent of hand dominance. Common sites include the eyelids, vulva and anus, the popliteal and antecubital fossae, and the neck. Other areas include the fold behind the ears, the lower legs, the ankles, and the upper thigh.
The morbidities associated with LSC include decreased or interrupted sleep, which affects motor and mental functioning; secondary infection; cosmetic disfigurement; scar or keloid development; and permanent skin-color alterations. LSC is not associated with increased mortality.
Like eczema, LSC is an “itch that rashes.” Early in the development of LSC, the skin is erythematous. Patients note that the pruritus is worst when they are in bed and about to go to sleep and that it is nonexistent or minimal during the daytime. Pruritus is usually intermittent; scratching provides temporary relief. Atopic patients may observe LSC in areas of previous atopic outbreaks. LSC sometimes occurs at sites of a previous irritant or allergic contact dermatitis, insect bites, or other minor skin trauma.
There is some neural basis for LSC. It seems likely that a relationship between neural tissue (both central and peripheral) and inflammatory cell products influences the perception of itch and the manifestation of lichenified skin. The nerve endings in the skin of the LSC patient are thought to manifest subtle changes related to the development of an itch-scratch-itch cycle. The more the eruption is scratched or rubbed, the more it itches, continuing the cycle.
The variants of LSC include frictional lichenoid dermatitis; pretibial pruritic papular dermatitis; unilateral, circumscribed, chronic dermatitis of the papillary-areolar areas; complex pebbly lichenification; and the giant lichenification of Pautrier (intertriginous LSC resembling a solid-tumor substantial plaque with a verrucuous cribriform surface, particularly in the genitocrural area). Some consider acne keloidalis nuchae
a variant of LSC with fibrotic keloidal scarring. Cutaneous horns have been noted to be histologic variants of LSC.
Treatment of LSC should be directed toward keeping patients from scratching. While physical barriers can aid in this regard, corticosteroids are the mainstay of treatments for LSC. It is probably best to start with class 1 ultrapotent corticosteroids, such as 0.05% halobetasol propionate, 0.1% diflucortolone valerate, or 0.05% clobetasol, for two weeks and then taper to less potent forms of treatment. Corticosteroid-impregnated tape is useful. Injections of corticosteroids into the lesion and around nerves enervating LSC can alleviate the urge to itch and thin the skin, helping to abate LSC.
A variety of noncorticosteroid topical treatments exists. Ice is very effective for relieving pruritus; crushed ice can be applied in a bag. Other treatments include topical forms of aspirin, nonsteroidal anti-inflammatory drugs, tacrolimus (Protopic), and pimecrolimus (Elidel); 5% doxepin or capsaicin cream, and botulinum toxin injections. OTC remedies include topical camphor and menthol (Sarna original), topical pramoxine 1% (Sarna Sensitive Skin), and topical camphor, menthol, pramoxine (Sarna Ultra). Chilling these lotions seems to increase their antipruritic effect. Topical antihistamines, such as topical benzocaine, should not be used, as they commonly result in contact sensitization and allergic contact dermatitis. Antihistamines given orally are useful for their sedating rather than their antipruritic effects. Oral doxepin and clonazepam can be useful for the same reasons and to reduce anxiety. Treatment of anogenital LSC is particularly challenging, and antidepressants may be required in patients refractory to treatment or with underlying psychiatric disorders. Topical preparations containing lidocaine (e.g., LMX4 or LMX5) can be used, particularly for anogenital LSC. The role of homeopathic remedies is uncertain. Interestingly, phototherapy has not been reported as a common treatment of LSC, perhaps because studies are directed against primary causes of itch, such as atopic dermatitis, rather than secondary effects, like LSC.
This patient was prescribed topical clobetasol 0.5% cream for two weeks. Once the itching had eased, she was put on maintenance therapy with triamcinolone 0.1% ointment. This course of therapy seemed to ease the problem so that she was no longer bothered.