Evaluating Baricitinib for Severe Paediatric Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) with Single-Cell Sequencing.

Purpose: Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe type of drug reaction that has significant mortality rate. Traditional treatments, including glucocorticoids and immunosuppressants, are sometimes insufficient. We present a case of severe paediatric DRESS unresponsive to conventional therapies, in which baricitinib, guided by single-cell RNA sequencing (scRNA-seq), led to clinical improvement. Single-cell transcriptomics is a revolutionary technology that allows scientists to measure the activity of all genes in individual cells on a large scale and has emerged as a tool for personalized therapeutic targeting. Patient and Methods: A 3-year-old male with DRESS triggered by phenobarbital presented with fever, skin rash, impaired liver function, eosinophilia, and cytomegalovirus infection. After failing high-dose corticosteroids, intravenous immunoglobulin, and etanercept, baricitinib was initiated. Peripheral blood mononuclear cells and skin biopsy samples underwent scRNA-seq to identify dysregulated pathways and potential therapeutic targets. Results: Baricitinib treatment led to resolution of skin lesions, normalization of eosinophil counts and liver function, and successful tapering of corticosteroids. Single-cell RNA sequencing uncovered that clusters of CD4+ and CD8+ T cells contain JAK2. Conclusion: Our findings suggest that baricitinib, a JAK1/2 inhibitor, is a safe and effective salvage therapy for corticosteroid-refractory paediatric DRESS. scRNA-seq can guide targeted treatment decisions in DRESS.