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From: Darlenski et al. Exp Rev Dermatol 2011. Genetic background. Epidermal barrier impairment. Immunologic disturbances. Atopic dermatitis. Environmental factors. Bieber T. Curr Allergy Asthma Rep. 2009 Elias P. JID 2009. Epidermal barrier impairment. Inflammation / itch.
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Genetic background Epidermal barrier impairment Immunologic disturbances Atopic dermatitis Environmental factors Bieber T. Curr Allergy Asthma Rep. 2009 Elias P. JID 2009
Epidermal barrier impairment Inflammation / itch Penetration of irritants Secretion of I inflammatory cytokines (IL-1, TNFα) by keratinocytes
Skin irritation in atopic dermatitis • The increased use of detergents is one of the most common causes for the atopic dermatitis exacerbation(Meding B. Br J Derm1987) • Higher irritant susceptibility in atopic subjects (Löfller H. Cont Derm 1999) • The increasing prevalence of atopic dermatitis is most probably due to the increasing use of detergents nowadays (Cork MJ et al. JACI 2006, JACI 2009)
Controversy on contact sensitization in atopic dermatitis (AD) AD = healthy AD↑ > healthy↓ • АD:Тh-2 ↔ contact allergy: Тh-1 • Lower DNCBsensitization in AD • (Rees J. Arch Dermatol 1990) • Epidemiology data • (Spiewak R. Ann Allergy Asthma Immunol 2005) • Нарушената бариера улеснява • пентрацията на хаптените • Filaggrin mutations associated • with contact allergy(Novak N et al. JID 2008) • Epidemiology data • (Klas P. Contact Derm 1996) АД
Irritation and sensitization in AD • Genetic factors • Mutations in the genes encoding filaggrin and SC proteases • Polymorphism in the IL-1; TNF-α genes Irritant А А А А Corneocyte Corneocyte Corneocyte Stratum corneum Corneocyte Corneocyte Secretion/synthesis of pro-inflammatory cytokines А Increased skin permeability/penetration APC Т Increased APC (Langerhans cells) density Increased expression of MHCmolecules MHC ICAM А Increased expression of ICAM
Key issues • Subjects with active atopic dermatitis (AD) show increased skin susceptibility to irritants, including subjective skin irritation (stinging) • Epidermal barrier impairment could be the basis for the increased response of the skin to irritant stimuli in atopic subjects. • Mucosal atopy most probably does not play a role in the exaggerated response to cutaneous irritants. • Data on contact hypersensitivity in atopic subjects is controversial • Filaggrin mutations are associated with contact allergy to nickel and particular types of hand dermatitis • Patch testing should be routinely performed in atopic subjects; however, the result must be interpreted cautiously. Contact allergy to certain allergens is more common in atopic subjects. As AD is a disease that can be provoked by external factors (such as contact allergy), patch testing may be helpful in disclosing contact hypersensitivity as a factor worsening the course of AD. This, in turn, would result in different therapeutic implications, for example, allergen avoidance.