funDERMentals

Leg Lesion Represents a Vicious Cycle

Joe Monroe discusses a common dermatologic problem in which the patient's behavior plays a key role.

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CASE

A 38-year-old man is referred to dermatology by his primary care provider (PCP) for evaluation of a lesion on his leg that has been present for more than two years. Concerned friends and family recently urged him to seek medical care.

His PCP thought it probably represented fungal infection, but the nystatin/triamcinolone cream he prescribed was of little or no help. The patient, who is of Indian descent, decided to consult a medical provider during a trip to India, but was dissatisfied with the herbal paste he was advised to obtain and use. When he returned to the United States, he requested referral to dermatology.

The patient denies any other skin problems, now or in the past, but admits to scratching and rubbing the site in question several times a day—partly out of habit, but mostly because it itches. The spot’s progressive darkening has been a major factor in his pursuit of further evaluation.

Examination reveals a single lesion: a uniformly scaly, dark, 8-x-4–cm area of his anterolateral calf. The margins of the lesion are fairly sharply demarcated, but there is no redness, increased warmth, or tenderness associated with it. The patient’s skin overall is quite dark (type V).

DISCUSSION

This presentation is typical of lichen simplex chronicus (LSC; also known as neurodermatitis)—essentially, a reaction to chronic rubbing and scratching. LSC is not a primary diagnosis; it is merely the consequence of mechanical trauma as a reaction to perceived pruritus (with or without actual pathologic cause). Over time, the affected skin tends to thicken in reaction to chronic trauma, which also has the effect of increasing pruritus. Thus, the itch-scratch-itch cycle perpetuates.

Affected skin also tends to darken, especially in darker-skinned patients, and is often the source of considerable consternation. Even when the condition is treated and all rubbing and scratching ceases, it may take months (if not years) for the hyperpigmentation to clear.

The keys to diagnosis include the patient’s admission of regular scratching and his ready access to the area, as well as the lichenification and hyperpigmentation. There are any number of initial triggers, including bug bites, dry skin, eczema, and even psoriasis. However, those conditions take a backseat to the LSC. This exact location (anterior leg) is quite typical in men, but in women, LSC is far more common in the nuchal scalp, where heat and sweat also contribute to the problem.

Many LSC patients have a history of atopic dermatitis that appears to lower their threshold for pruritus. When questioned closely, many if not most will admit to concurrent emotional stress, which is thought to be a contributing factor.

Biopsy is occasionally necessary to distinguish LSC from other items in the differential, including psoriasis, contact dermatitis, and lichen planus. But in most cases, including this one, the twice-daily application of a class 2 or 3 topical steroid cream or ointment for one to two weeks will work wonders. Educating the patient about his own contribution to the problem is essential.

This patient was instructed to return in one month, to ensure that the condition was responding and that he understood the need to gradually decrease the use of this powerful steroid. Unfortunately, his chances for recurrence are quite high, given the habitual and compelling nature of the problem.

TAKE-HOME LEARNING POINTS

• Lichen simplex chronicus (LSC) is a very common condition that represents the skin’s reaction to chronic scratching and rubbing.

• LSC is not a primary condition; rather, it is triggered by dry skin, eczema, contact dermatitis, or lichen planus (among others).

• LSC involves thickening of the affected skin and, in darker-skinned patients, a reactive hyperpigmentation.

• LSC commonly manifests on the anterior legs in men and on the nuchal scalp in women.

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