Hypogammaglobulinemia and infection after administration of rituximab for steroid-dependent nephrotic syndrome

The frequency of rituximab (RTX) use increases in complicated nephrotic syndrome (NS), raising concerns about infections associated with low IgG due to combination therapy with RTX and immunosuppressants. Between February 2008 and June 2017, we enrolled 74 children with complicated steroid-dependent NS (178 total RTX administrations, 13.8 years average patient age at time of administration) and retrospectively assessed prevalence of hypogammaglobulinemia (IgG level < 500 mg/dl) and infection. Twenty doses (11%) were associated with hypogammaglobulinemia at 6 months after RTX administration. The average age (6.1 vs 14.4 years old, p < 0.01) and serum IgG levels before administration of RTX (426 vs 656 mg/dl, p < 0.01) were significantly lower in the hypogammaglobulinemia group. Among 15 patients we were able to observe for 1 more year, 8 patients had persistent hypogammaglobulinemia, and the use of mycophenolate mofetil (MMF) was significantly higher (78 vs 17%, p < 0.05. IgG replacement therapy was performed in two patients whose IgG levels declined over time. In this study, only one varicella infection was noted. IgG replacement therapy should be considered on a case by case basis.