Idiopathic nephrotic syndrome and rituximab: may we predict circulating B lymphocytes recovery?

Background: Rituximab (RTX) has been shown to be an efficient treatment for steroid-dependent nephrotic syndrome (SDNS). A long B cell depletion period seems to improve the duration of remission. This study reports the duration of B cell depletion after each RTX infusion in patients with nephrotic syndrome.

Methods: We retrospectively report the data of 22 patients with a diagnosis of a SDNS or steroid-resistant nephrotic syndrome (SRNS) and a treatment with RTX in a single center. B cell depletion duration was compared to the first B cell depletion duration and to the previous B cell depletion duration in each patient.

Results: Twenty-two patients (5 girls) were included. Seventy-six periods of B cell depletions were compared to the first B cell depletion duration and to the preceding B cell depletion duration in the same patient. Total duration of B cell depletion was 26 (6-66) months. Individual post-RTX infusion B cell depletion duration was 5.1 (1.6-14) months. Median B cell depletion duration following the first RTX cure for children who had received 1 to 2 infusions at first cure was not statistically different of those who had received 3 to 4 infusions (p = 0.18). Comparing the B cell depletion induced by previous RTX courses and the following B cell depletion, 89.5% of patients had a similar duration within an open interval from 2 months.

Conclusion: Once the individual time interval until B cell recovery is determined, monitoring could be individualized by targeting the expected date of B cell recovery or by performing pre-emptive RTX injections.