Regulatory T cells and plasmacytoid dendritic cells in drug rash with eosinophilia and systemic symptoms VS maculopapular drug eruption: A serological pilot study.

BACKGROUND Regulatory T (Treg) cells and plasmacytoid dendritic cells (pDCs) are involved in the pathogenesis of drug rash with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome (DRESS/DIHS).

OBJECTIVES To compare circulating Treg cells and pDCs at different stages among patients with DRESS/DIHS, patients with maculopapular drug eruption (MPE), and healthy subjects, and to assess circulating Treg cells and pDCs at post-steroid cessation in DRESS/DIHS.

MATERIAL AND METHODS This was a cross-sectional study that enrolled adult patients diagnosed with DRESS/DIHS and MPE. Blood samples were obtained from the patients at the initial presentation (acute phase), 1 week later (subacute phase), during the 3rd week (resolution phase), and post-steroid cessation for DRESS/DIHS. Healthy subjects' blood samples were also taken. Peripheral blood mononuclear cells were isolated for flow cytometry analysis.

RESULTS A total of 22 patients participated in this study: patients with DRESS/DIHS (n = 9), patients with MPE (n = 8), and healthy subjects (n = 5). During the acute stage of DRESS/DIHS and MPE, the mean percentage of Treg cells and pDCs significantly decreased compared to healthy subjects. However, Treg cells showed a progressive increase towards the resolution phase in both conditions, while pDCs continued to decrease towards the resolution phase. Following steroid discontinuation in DRESS/DIHS, both Treg cells and pDCs showed a progressive increase in number.

CONCLUSIONS Treg cells and pDCs play a role in DRESS/DIHS and MPE pathogenesis, evidenced by the fluctuation in their percentages at each stage of both conditions. However, increased circulating Treg cells may crucially mitigate inflammation in both conditions.