Epidermal barrier dysregulation in atopic skin predisposes for excessive growth of the allergy-associated yeastMalassezia

Abstract

The skin barrier is vital for protection against environmental threats including insults caused by skin-resident microbes. Dysregulation of the barrier is a hallmark of atopic dermatitis (AD) and ichthyosis, with variable consequences for host immune control of colonizing commensals and opportunistic pathogens. While sensitisation toMalassezia, the most abundant commensal fungus of the skin, is common in AD, its relevance for pathogenesis remains unclear. Here we show that in barrier-disrupted skin,Malasseziaacquires enhanced fitness. This is not a consequence of the dysregulated allergic immune status characteristic for AD but is rather explained by structural and metabolic changes in the cutaneous niche that provide increased accessibility and a favourable lipid profile, to which the lipid-dependent yeast adapts for enhanced nutrient assimilation. These findings reveal fundamental insights into the role of the mycobiota in the pathogenesis of common skin barrier disorders.