Chapter 053. Eczema and Dermatitis (Part 3)

Lichen Simplex Chronicus Lichen simplex chronicus may represent the end stage of a variety of pruritic and eczematous disorders, including atopic dermatitis. It consists of a circumscribed plaque or plaques of lichenified skin (thickening of the skin and accentuation of normal skin markings) due to chronic scratching or rubbing. Common areas involved include the posterior nuchal region, dorsum of the feet, and ankles. Treatment of lichen simplex chronicus centers on breaking the cycle of chronic itching and scratching. High-potency topical glucocorticoids are helpful in most cases, but in recalcitrant cases, application of topical glucocorticoids under occlusion, or intralesional injection...
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Chapter 053. Eczema and Dermatitis (Part 3) Chapter 053. Eczema and Dermatitis (Part 3) Lichen Simplex Chronicus Lichen simplex chronicus may represent the end stage of a variety ofpruritic and eczematous disorders, including atopic dermatitis. It consists of acircumscribed plaque or plaques of lichenified skin (thickening of the skin andaccentuation of normal skin markings) due to chronic scratching or rubbing.Common areas involved include the posterior nuchal region, dorsum of the feet,and ankles. Treatment of lichen simplex chronicus centers on breaking the cycle ofchronic itching and scratching. High-potency topical glucocorticoids are helpful inmost cases, but in recalcitrant cases, application of topical glucocorticoids underocclusion, or intralesional injection of glucocorticoids may be required. Oralantihistamines such as hydroxyzine (10–25 mg every 6 h) or tricyclicantidepressants with antihistaminic activity, such as doxepin (10–25 mg atbedtime), are useful primarily due to their sedating action. Higher doses of theseagents may be required, but sedation can become bothersome. Patients need to becounseled regarding driving or operating heavy equipment after taking thesemedications. Contact Dermatitis Contact dermatitis is an inflammatory process in skin caused by anexogenous agent or agents that directly or indirectly injure the skin. This injurymay be caused by an inherent characteristic of a compound—irritant contactdermatitis (ICD). An example of ICD would be dermatitis induced by aconcentrated acid or base. Agents that cause allergic contact dermatitis (ACD)induce an antigen-specific immune response (poison ivy dermatitis). The clinicallesions of contact dermatitis may be acute (wet and edematous) or chronic (dry,thickened, and scaly), depending on the persistence of the insult (see Fig. 52-10). Irritant Contact Dermatitis ICD is generally well demarcated and often localized to areas of thin skin(eyelids, intertriginous areas) or to areas where the irritant was occluded. Lesionsmay range from minimal skin erythema to areas of marked edema, vesicles, andulcers. Chronic low-grade irritant dermatitis is the most common type of ICD, andthe most common area of involvement is the hands (see below). The mostcommon irritants encountered are chronic wet work, soaps, and detergents.Treatment should be directed to avoidance of irritants and use of protective glovesor clothing. Allergic Contact Dermatitis ACD is a manifestation of delayed-type hypersensitivity mediated bymemory T lymphocytes in the skin. The most common cause of ACD is exposureto plants, especially to members of the family Anacardiaceae, including the genusToxicodendron. Poison ivy, poison oak, and poison sumac are members of thisgenus and cause an allergic reaction marked by erythema, vesiculation, and severepruritus. The eruption is often linear or angular, corresponding to areas whereplants have touched the skin. The sensitizing antigen common to these plants isurushiol, an oleoresin containing the active ingredient pentadecylcatechol. Theoleoresin may adhere to skin, clothing, tools, and pets, and contaminated articlesmay cause dermatitis even after prolonged storage. Blister fluid does not containurushiol and is not capable of inducing skin eruption in exposed subjects. Contact Dermatitis: Treatment If contact dermatitis is suspected and an offending agent is identified andremoved, the eruption will resolve. Usually, treatment with high-potency topicalglucocorticoids is enough to relieve symptoms while the dermatitis runs its course.For those patients who require systemic therapy, daily oral prednisone beginningat 1 mg/kg, but usually ≤60 mg/d, is sufficient. It should be tapered over 2–3weeks, and each daily dose given in the morning with food. Identification of a contact allergen can be a difficult and time-consumingtask. Patients with dermatitis unresponsive to conventional therapy or with anunusual and patterned distribution should be suspected of having ACD. Theyshould be questioned carefully regarding occupational exposures and topicalmedications. Common sensitizers include preservatives in topical preparations,nickel sulfate, potassium dichromate, thimerosal, neomycin sulfate, fragrances,formaldehyde, and rubber-curing agents. Patch testing is helpful in identifyingthese agents but should not be attempted on patients with widespread activedermatitis or on those taking systemic glucocorticoids. Hand Eczema Hand eczema is a very common, chronic skin disorder in which bothexogenous and endogenous factors play important roles. It may be associated withother cutaneous disorders such as atopic dermati ...