Phenotypes of atopic dermatitis

Atopic dermatitis (AD) is a common disease affecting both children and adults. AD develops from a complex interplay between environmental, genetic, immunologic and biochemical factors. Genetic factors predispose atopic subjects to mount exaggerated Th2 responses and to a poorly efficient epidermal barrier, which may be sufficient to initiate inflammation in the skin and may favor allergic sensitization. Thus AD can present with different clinical phenotypes. AD is classically distinguished into an intrinsic and extrinsic form, which are clinically identical but the former lacks high level specific IgE and is not associated with respiratory atopy. Although in many cases AD presents with monotonous eczematous lesions on the face, neck and skin folds, it may also present with other features. Very common is nummular eczema, which in many instances may be the dominant expression of AD. In other patients, AD affects limited areas (periorificial eczema, nipple eczema, cheilitis, hand eczema) or its main presentation is with excoriated papules and nodules (atopic prurigo). In conclusion, AD is a multifaceted disease affecting patients with epidermal barrier dysfunction and dry and sensitive skin. The recognition of the less common AD phenotypes is essential for proper patient management.