Abundant immunoglobulin E‐positive cells in skin lesions support an allergic etiology of atopic dermatitis in the elderly

<jats:title>Abstract</jats:title><jats:p><jats:bold>Background/Objectives </jats:bold> Atopic dermatitis (AD) in the elderly is gradually increasing in industrialized countries in association with the aging of society. We report herein four cases of elderly AD {three extrinsic [immunoglobulin (Ig)E‐mediated allergy]; one intrinsic (non‐IgE‐allergy)} in which we investigated the presence of IgE+ cells in lesional skin.</jats:p><jats:p><jats:bold>Methods/Results </jats:bold> Single immunohistochemical and double immunofluorescence stainings were performed for skin biopsy specimens from AD patients and non‐atopic control subjects with chronic eczema. In the lesional lichenified skin of patients with extrinsic elderly AD, numerous IgE+ cells were found among inflammatory cells infiltrates in the upper dermis. Comparative analysis of single immunohistochemistry results using serial paraffin and/or frozen sections found that many IgE+ cells showed identical distributions to tryptase+ mast cells. IgE+ cells coincident with CD1a+ Langerhans cells in the epidermis were found in small numbers only in frozen sections. Double immunofluorescence staining for IgE and CD11c revealed cells coexpressing IgE and CD11c with a dendritic morphology in the papillary and upper dermis. These IgE+ mast cells and IgE+ CD11c+ cells were also found in cured normal‐looking skin from a patient with extrinsic elderly AD after successful treatment. Although only a few weakly positive IgE+ cells were detected, no IgE+CD11c+ cells were found in specimens from patients with intrinsic elderly AD or non‐atopic chronic eczema.</jats:p><jats:p><jats:bold>Conclusion </jats:bold> IgE‐mediated allergic inflammation may play an important role in the pathobiology of elderly AD, similar to other age groups of AD.</jats:p>