Case Report: Relapse of SLE associated with EBV infection in a patient after CAR-T cell therapy: a clinical case.

We present the case of a 13-year-old boy with refractory systemic lupus erythematosus (SLE) who achieved drug-free remission after anti-CD19 CAR-T cell therapy, but subsequently experienced Epstein-Barr virus (EBV) reactivation on day 142 after CAR T-cell infusion and peak EBV load was 24,400 IU/mL with a severe drop in platelets to 8×109/L, which leading to relapse of SLE and manifestations of chronic active EBV disease (CAEBVD). The whole exogenous gene testing found X chromosome Xp22.33q28 region (chrX: 200855-155239820) a duplicate of about 155.04Mbp,which is associated with the development of Klinefelter syndrome (KS).The temporal association between EBV resurgence and SLE flare suggests that CAR-T-induced immunosuppression with some genetic background may permit EBV reactivation, which can be associated with the return of autoimmunity. This case highlights the need for vigilant monitoring for opportunistic infections and genetic background, particularly EBV, after CAR-T therapy for autoimmune diseases, as they may contribute to disease relapse.