A distinct lymphocyte distribution in relapse after rituximab for steroid-dependent nephrotic syndrome

Rituximab (RTX) is a new steroid-sparing therapy for childhood steroid-dependent nephrotic syndrome (NS). However, relapses frequently occur immediately after CD19 recovery. We report the cases of two steroid-dependent NS patients treated with RTX followed by mizoribine (MZB). One patient relapsed, and the other developed proteinuria after CD19 recovery until the MZB was replaced by mycophenolate mofetil. These patients exhibited different lymphocyte phenotypes, with the CD4+/CD8+ profile favoring CD8+ T lymphocytes, while CD3+ HLA-DR-expressing activated T lymphocyte expansion occurred in the relapsed patient. Based on these findings, we suggest that T cell activation may influence outcome and that phenotypic analysis in addition to B cell monitoring may facilitate the detection of NS relapse.