Overview of atopic dermatitis

Abstract

Atopic dermatitis (AD) is a very common chronic disease that reportedly affects 10%-20% of the general population. The prevalence of AD appears to be steadily increasing, at least in developing countries. Two pathogenetic mechanisms have been mentioned. Traditionally immunological aberrations are thought to be a primary event in the initial development of AD ("inside-to-outside hypothesis"). Another hypothesis assumes that there is an intrinsic defect in epidermal barrier. Due to this barrier defect, allergens or irritants can easily penetrate the epidermal barrier, and induce immunologic reaction secondarily ("outside-to-inside hypothesis"). These days the epidermal barrier defect seems to gain more support as a primary event than immunological aberrations in the early changes of AD since the filaggrin mutation was reported in AD patients. Clinically AD initially affects face, and with age, flexural areas are typically involved. AD has many different clinical features. Diagnostic criteria for AD in each country may be a little different, although based on the criteria proposed by Hanifin and Rajka. AD can be controlled effectively with topical and/or systemic treatments and fortunately spontaneously disappears with age. However, in some cases very resistant to conventional therapies, additional treatments such as immunosuppressive agents are needed.

Keywords: Atopic dermatitis; Epidermal barrier defect; Filaggrin mutation; Immunological aberrations; Prevalence.

Fig. 1

Two pathogenetic mechanisms. Which one is first, immunological aberrations (inside-to-outside hypothesis) or epidermal barrier defect (outside-to-inside hypothesis)? These days more emphasis is given to barrier defect in the early changes in the evolution of AD ever since FLG mutation was reported. FLG, filaggrin; Epid, epidermis; TEWL, transepidermal water loss; AD, atopic dermatitis.

Fig. 2

Perioral area typically affected first due to irritation of saliva.

Fig. 3

Flexural areas are typically affected in patients over 2 yr.

Fig. 4

Periauricular eczematization.