Significance of Molecular Monitoring of T Cells for the Decision of Treatment Strategy for Epstein-Barr Virus-associated Hemophagocytic Lymphohistiocytosis

A 17-year-old patient with Epstein-Barr virus (EBV)-associated hemophagocytic lymphohistiocytosis achieved first remission after immunochemotherapy (ICT). However, he had fever with an increase in soluble interleukin-2 receptor, but not in ferritin. Molecular analysis revealed augmented plasma and T-cell EBV loads and reappearance of clonal T cells. Despite achieving second remission, the T-cell EBV load at week 8 after second ICT was almost similar to that at week 8 after first ICT. Hence, cyclosporine was decreased over a 9-month period, with molecular monitoring of plasma and T cells. In this article, we describe how useful molecular monitoring was for detecting relapse and resuming ICT.