A Case of Cutaneous Fungal Infection Following the Administration of Dupilumab.

Atopic dermatitis (AD) is a chronic inflammatory skin condition with a multifactorial etiology. Herein, we report a case of a patient with AD undergoing long-term topical treatments who developed a dermatophyte infection following the administration of dupilumab. Dupilumab is known to enhance skin barrier function and induce changes in the skin microbiome. Notably, head and neck dermatitis caused by the overgrowth of species due to dupilumab has been widely discussed. This phenomenon is thought to result from the suppression of T helper (Th)2 cytokines by dupilumab, leading to a decrease in the proportion of and a relative increase in fungal populations. Additionally, feedback activation of Th17 cytokines may trigger excessive inflammation against fungi, contributing to fungal infections. IL-13 plays critical roles in fungal colony formation, and tralokinumab, an IL-13 inhibitor, has shown potential efficacy in treating this head and neck dermatitis. While the relationship between microbiome changes and biologics like lebrikizumab and nemolizumab remains unexplored, investigating the differential effects of these therapies on the cutaneous microbiome could provide deeper insights into not only the unique characteristics of each biologic agent but also the roles of Th2 cytokines such as IL-4, IL-13, and IL-31 in the pathophysiology of AD. The present case underscores the importance of the comprehensive therapeutic approach for AD that accounts for microbiome dynamics and adapts to evolving skin changes throughout the course of treatment.