Different effects of pimecrolimus and betamethasone on the skin barrier in patients with atopic dermatitis

Background: Genetic defects leading to skin barrier dysfunction were recognized as risk factors for atopic dermatitis (AD). It is essential that drugs applied to patients with AD restore the impaired epidermal barrier to prevent sensitization by environmental allergens. Objectives: We investigated the effect of 2 common treatments, a calcineurin inhibitor and a corticosteroid, on the skin barrier. Methods: In a randomized study 15 patients with AD were treated on one upper limb with pimecrolimus and on the other with betamethasone twice daily for 3 weeks. Results: Stratum corneum hydration and transepidermal water loss, a marker of the inside-outside barrier, improved in both groups. Dye penetration, a marker of the outside-inside barrier, was also reduced in both drugs. Electron microscopic evaluation of barrier structure displayed prevalently ordered stratum corneum lipid layers and regular lamellar body extrusion in pimecrolimus-treated skin but inconsistent extracellular lipid bilayers and only partially filled lamellar bodies after betamethasone treatment. Both drugs normalized epidermal differentiation and reduced epidermal hyperproliferation. Betamethasone was superior in reducing clinical symptoms and epidermal proliferation; however, it led to epidermal thinning. Conclusion: The present study demonstrates that both betamethasone and pimecrolimus improve clinical and biophysical parameters and epidermal differentiation. Because pimecrolimus improved the epidermal barrier and did not cause atrophy, it might be more suitable for long-term treatment of AD. (J Allergy Clin Immunol 2009;123:1124-33.)