Eczema herpeticum in atopic dermatitis

Atopic dermatitis (AD) is one of the most common chronic inflammatory skin disease leading to pruritic skin lesions. A subset of AD patients exhibitsa disseminated severe HSV infection called eczema herpeticum (EH) which can cause life-threatening complications. This review gives an overview of the clinical picture, and characteristics of the patients as well as the diagnosis and therapy of EH. A special focus lies on the pathophysiological hallmarksidentified so farthat predispose for EH. This aspect coversgenetic aberrations, immunological changes and environmental influences displaying a complex multifactorial situation, which is not completely understood.Type 2 skewing of virus-specific T cells in ADEH+ patients has been implicated in immune profile abnormalities, along withimpaired functions of dendritic cells and natural killer cells. Furthermore, aberrations ininterferon pathway related genes such as IFNG and IFNGR1 have been identified to increase the risk of EH. IL-4, IL-25, and thymic stromal lymphopoietin (TSLP) are overexpressed in EH, whereas antimicrobial peptides like humanβ-defensinsand LL-37 are reduced. Concerning the epidermal barrier, single nucleotide polymorphisms (SNPs) in skin barrier proteins such as filaggrin were identified in ADEH+ patients. A dysbalance of theskin microbiomealso contributes to EH due to an increase of Staphylococcus aureus, which provides asupporting role to the viral infection via secreted toxins such as a-toxin. The risk of EH is reduced in AD patients treated with dupilumab. Further research is needed to identify and specifically target risk factors for EH in AD patients.