Atopic dermatitis and psoriasis: two different immune diseases or one spectrum?

Area of Science:

• Immunodermatology
• Molecular biology
• Inflammatory skin diseases

Background:

• Psoriasis and atopic dermatitis (AD) are common T-cell mediated inflammatory skin diseases.
• Epidermal keratinocytes respond to T-cell cytokines, influencing disease phenotypes.
• Psoriasis is Th17-driven (IL-17), while AD is Th2-driven (IL-4, IL-13), with both involving Th22 and Th1 pathways.

Purpose of the Study:

• To explore the relationship between psoriasis and AD, considering their distinct and overlapping molecular phenotypes.
• To investigate the potential for a spectrum model encompassing different AD subtypes with varying T-cell involvements.
• To address the question of whether targeting single or multiple cytokine axes is optimal for treating AD compared to psoriasis.

Main Methods:

• Comparative analysis of T-cell polarity and cytokine profiles in psoriasis and AD.
• Examination of epidermal keratinocyte responses to T-cell derived cytokines.
• Review of current treatment strategies targeting specific cytokine axes (e.g., IL-23/Th17 in psoriasis).

Main Results:

• Psoriasis and AD exhibit distinct T-cell profiles (Th17 vs. Th2), but share Th22 and Th1 pathway activation.
• Certain AD subtypes (e.g., Asian-origin, intrinsic, pediatric) show prominent IL-17 involvement, overlapping with psoriasis histopathology.
• Current psoriasis treatments effectively target the IL-23/Th17 axis, achieving high disease control.

Conclusions:

• Psoriasis and AD may represent points on a spectrum, with variable T-cell axes contributing to disease phenotypes.
• The heterogeneity of AD, particularly subtypes with IL-17 activity, challenges a singular treatment approach.
• Personalized therapy targeting multiple T-cell axes may be necessary for effective AD treatment, analogous to psoriasis management.