dermatitis, thrombocytopenia, small-sized platelets, and recurrent infections. Langerhans cell histiocytosis is characterized by hemorrhagic or petechial lesions. Scabies is an intensely pruritic skin condition caused by the human scabies mite. The presence of a burrow found in the web spaces of the fingers, the flexor surfaces of the wrists, elbows, axilla, or genitals is pathognomonic. Burrows may be few in number or absent, however.
The goals of therapy are to reduce the number and severity of flares and to increase the number of disease-free periods. Successful management involves skin hydration, pharmacologic therapy to reduce pruritus, and identification and avoidance of triggers. Patients with atopic dermatitis have a decrease in skin barrier function and enhanced transepidermal water loss. Daily, lukewarm baths for 15 to 20 minutes followed immediately by the application of fragrance-free emollients to retain moisture are a major component of therapy. Prevention of xerosis is important for control of pruritus and for maintaining the integrity of the epithelial barrier. Emollients should be ointments or creams, such as petrolatum, Aquaphor, Eucerin, or Cetaphil. Lotions are not as effective because they contain water or alcohol and may have a drying effect owing to evaporation. A mild nonsoap cleanser also is recommended.
Topical anti-inflammatory agents, including corticosteroids and immunomodulators, are the cornerstone of therapy for acute flares and prevention of relapses. Topical corticosteroids are used for reducing inflammation and pruritus; they are effective for the acute and chronic phases of the disease. Ointments generally are preferred over creams and lotions because of enhanced potency and skin penetration. Corticosteroids are ranked by potency into seven classes. The least potent corticosteroid that is effective should be used. Higher potency corticosteroids may be necessary to diminish the dermatitis flare but should be used for limited periods. Low-potency, nonfluorinated corticosteroids should be used on the face, intertriginous areas (groin, axilla), and large areas to reduce the risk of adverse effects. Reduced efficacy of topical corticosteroids may be related to disease severity rather than glucocorticoid resistance. Local adverse effects, such as skin atrophy and striae, and systemic adverse effects, such as hypothalamic-pituitary-adrenal axis and growth suppression and hyperglycemia, are related to the potency, length of use, and extent of medication application. In infants and younger children, the possibility of corticosteroid-induced adverse effects may be greater. When control of inflammatory lesions is achieved, most patients can be managed with emollients and low-potency topical corticosteroids.
The topical immunomodulating drugs, tacrolimus and pimecrolimus, are approved as second-line agents for short-term and intermittent treatment of atopic dermatitis in patients unresponsive to or intolerant of other therapies. They are approved for use in children older than 2 years of age. These agents may be used on all body locations and are especially useful on delicate skin sites, such as the face, neck, and axilla without the adverse effect of cutaneous atrophy seen with topical corticosteroids. These medications have a potential increased cancer risk, and their long-term safety has not been established. Other less serious adverse effects include local burning and the need for sun protection.