[Incidence of hypogammaglobulinaemia in children with steroid-dependent/frequently relapsing nephrotic syndrome treated with rituximab and its association with severe infections]

Objective: To investigate the incidence and influencing factors of hypogammaglobulinemia (HGG) in children with steroid-dependent/frequently relapsing nephrotic syndrome (SDNS/FRNS) treated with rituximab (RTX), and its relationship with the risk of severe infections. Methods: The clinical data of children with SDNS/FRNS treated with RTX at the Department of Pediatrics of the First Affiliated Hospital of Zhengzhou University from December 2020 to January 2023 were retrospectively analyzed. RTX treatment was performed using a B-cell-guided regimen (a single dose of 375 mg/m2, a maximum of 500 mg/dose, and an additional one dose when reassessment of peripheral blood CD19+B cells≥1%). Patients were divided into HGG and non-HGG groups according to the presence or absence of HGG during the follow-up period. A multivariate logistic regression model was used to analyze the influencing factors of HGG, and the predictive value of each influencing factor on HGG was assessed by plotting the receiver operating characteristic (ROC) curve. Results: A total of 59 SDNS/FRNS children (48 males and 11 females) were included, and aged [M (Q1, Q3)] 9.4 (6.5, 12.2) years at the time of the first RTX treatment, with a median application of 3 (2, 4) doses of RTX. During the follow-up period of 15.5 (9.9, 22.8) months, the HGG was present in 16 (27.1%) children, of which seven persisted for more than 1 year. Compared with non-HGG group, HGG group had a shorter duration of the disease [3.3 (2.1, 3.6) vs 4.6 (2.4, 8.0) years, P=0.030], younger age at the time of the first RTX treatment [6.2 (5.6, 7.4) vs 11.3 (8.8, 13.3) years, P<0.001], and lower serum IgG levels [5.9 (4.9, 6.4) vs 7.5 (6.1, 8.2) g/L, P<0.001]. Multivariate logistic regression analysis showed that young age at the time of the first RTX treatment (OR=0.52, 95%CI: 0.35-0.78, P=0.002) was an influencing factor of HGG. The area under the curve (AUC) for age at first RTX treatment to predict HGG was 0.887 (95%CI: 0.778-0.955, P<0.001), with an optimal cut-off value of 8.3 years. During the follow-up period, six children (10.2%) developed severe infectious, and there was no statistically significant difference in the incidence of serious infections between the HGG and non-HGG groups [12.5% (2/16) vs 9.3% (4/43), P=1.000]. Conclusions: HGG is frequent in children with SDNS/FRNS treated with RTX, and nearly half of HGG persists for more than 1 year. The possibility of HGG is greater in those≤8.3 years at the first RTX treatment, but HGG does not increase the risk of severe infections in children.