Increased expression of in situ CD123 and reduced Toll‐like receptor 7/9 signalling pathway suggest impaired activation of plasmacytoid dendritic cells in recurrent erythema multiforme.

This article examines the expression and activity of plasmacytoid dendritic cells (pDCs) in patients with recurrent erythema multiforme (REM), a condition characterized by repeated outbreaks of erythema multiforme (EM). The study found that REM patients had increased expression of CD123, a marker for pDCs, in the epidermis and dermis. However, they also had reduced expression of Toll-like receptor 9 (TLR9), which suggests impaired activation of pDCs. The authors hypothesize that this impaired activation may contribute to the persistence of herpes simplex virus (HSV) and REM episodes. Further research on the role of reduced TLR9 expression in REM patients could lead to new targeted therapies. [Extracted from the article]