Lichen simplex chronicus (LSC) is thickening of the skin with variable scaling that arises secondary to repetitive scratching or rubbing. Lichen simplex chronicus is not a primary process. Rather, a person senses pruritus in a specific area of skin (with or without underlying pathology) and causes mechanical trauma to the point of lichenification.
A proposed variant of lichen simplex chronicus is lichen amyloidosis. Lichen amyloidosis is described as lichen simplex chronicus in which the keratinocytes have necrosed and formed keratinocytic-derived amyloid in the dermis. The initial insult is pruritus with resultant amyloid formation, rather than the reverse. [1, 2]
Lichen simplex chronicus is found on the skin in regions accessible to scratching. Pruritus provokes rubbing that produces clinical lesions, but the underlying pathophysiology is unknown. Some skin types are more prone to lichenification, such as skin that tends toward eczematous conditions (ie, atopic dermatitis, atopic diathesis). A relationship likely exists between central and peripheral neural tissue and inflammatory cell products in the perception of itch and ensuing changes in lichen simplex chronicus. Emotional tensions, such as in patients with anxiety, depression, or obsessive-compulsive disorder, may play a key role in inducing a pruritic sensation, leading to scratching that can become self-perpetuating. [3, 4, 5, 6] The possible interplay among primary lesions, psychic factors, and the intensity of pruritus additively influence the extent and severity of lichen simplex chronicus.
A small study looking at lichen simplex chronicus and the use of P-phenylenediamine (PPD)–containing hair dye showed clinically relevant improvement in symptoms after discontinuation of PPD exposure, thus providing a basis for the role of sensitization and contact dermatitis in the etiology of lichen simplex chronicus.
Exact frequency in the general population is unknown. In one study, 12% of aging patients with pruritic skin had lichen simplex chronicus.
No differences are reported in frequency among races, although prior authors claimed lichen simplex chronicus was more common in Asians and African Americans. The appearance of lesions on darker skin sometimes shows follicular prominence. Secondary pigmentary alterations are also more severe in individuals with darker skin.
Lichen simplex chronicus is observed more commonly in females than in males. Lichen nuchae is a form of lichen simplex that occurs on the midposterior neck and is observed almost exclusively in women.
Lichen simplex chronicus occurs mostly in mid-to-late adulthood, with highest prevalence in persons aged 30-50 years.
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