DISCUSSION
This is an archetypical case of lichen simplex chronicus (LSC), previously known as neurodermatitis. LSC is, by definition, a secondary condition, starting with a bit of eczema, dry skin, or even a bug bite that draws the patient’s attention to the area.
For some, once the itching and scratching start, it becomes hard to stop, although the original insult is long gone. Scratched or rubbed long enough, the affected skin reacts by becoming thick and leathery. In patients with darker skin, postinflammatory hyperpigmentation will also be seen.
But the worst effect is that, in response to chronic scratching, the nerves in the affected area become more numerous and even more sensitive. It’s the classic “itch-scratch-itch” cycle that takes on a life of its own until broken. Even then, many patients resume scratching at some point, purely out of habit.
Effective treatment has three components: First, the patient has to apply a relatively strong topical steroid, usually twice a day, to reduce the itching. This paves the way for the second phase of treatment: cessation of scratching. Within a fairly short period of time, the skin will begin to lose its rough feel and hyperpigmentation and look more normal. Then the third part of successful treatment: The patient must stop looking for the cause and begin to understand his/her role in the perpetuation of the problem.
The differential for LSC includes psoriasis, eczema, lichen planus, and xerosis (dry skin). But the key features of LSC, illustrated nicely by this case, are: easily accessible area, chronicity (sometimes extreme), and lichenification and postinflammatory hyperpigmentation. This patient’s history of chronic excoriation of the site was an extremely helpful diagnostic clue.
TAKE-HOME LEARNING POINTS
• Lichen simplex chronicus (LSC) is always secondary to another trigger, such as dry skin, eczema, bug bite, or minor skin injury that itches as it heals.
• LSC is characterized by localized thickening of the skin in an accessible area.
• Legs (especially the anterior tibial area) are common sites, but so is the nuchal scalp—particularly in women.
• LSC is treated with a potent topical steroid cream (eg, clobetasol 0.05%) and education of the patient as to his/her role in the creation and perpetuation of the problem.