Understanding the atopic dermatitis-psoriasis phenotypic switch through a mechanistic epidemiology approach

Abstract Atopic Dermatitis (AD) and psoriasis (PsO) are two frequent dermatologic conditions that may co-occur in a cluster of patients, yet current understanding of how these two conditions relate to one-another remains poorly understood. One way to better understand their relationship is through a process called phenotypic switching, where AD and PsO can turn into one another. We utilized a pharmacovigilance-based epidemiological approach to better understand this phenomenon. By generating adverse event-related disproportionality signals for various therapies and therapeutic classes used in AD and PsO, several potential mechanisms for the AD-PsO phenotypic switch were uncovered. This includes mechanisms involving T H 2 and T H 22 repolarization, T H 17 and T H 22 repolarization, and immune shifting between T H 1, T H 17, and T H 2 cells. Clinically and immunologically related conditions were also analyzed to gain a clearer understanding of the specificity of the switch from PsO to an eczematous phenotype. Together, these findings provide mechanistic insight into the underpinnings behind the AD-PsO phenotypic switch through a novel approach, adding evidence to the fluid nature of immune phenotypes in common medical conditions. One Sentence Summary The atopic dermatitis-psoriasis phenotypic switch creates an overlap phenotype that is likely T H 22-driven.