Rituximab, the anti-CD20 monoclonal antibody, is effective in reducing relapses in nephrotic syndrome. Published series have predominantly used 1.5g/m² over 2–4 doses. With the lowest effective dose to be elucidated, balancing this against potential long-term side effects is important. We report our experience with a single 375mg/m² dose.

We retrospectively examined notes of 20 patients with FRNS/SDNS treated over 6 years at a regional centre. Nineteen patients received a first dose of 375mg/m²; 1 patient received a second dose after 14 d.

Eleven patients were male. The median age at diagnosis was 3.5 years (range: 1.8–11.3). Time from diagnosis to first dose was 5.5 years (2.3–11.3). One or more renal biopsies were performed in 18 patients: minimal change disease was seen initially in all patients; calcineurin-inhibitor toxicity was seen in 9 patients prior to rituximab. Following a first dose, 4 patients have remained in remission (median follow-up 734 days). Time to B cell depletion (<0.2×10⁹/L) after first dose was 17.5 days (0–75). Five patients received a prophylactic 2nd dose after 180 days (148–321). The remaining 11 patients relapsed after 272 days (149–-568) and received a 2nd dose after 321 days (154–616). In total, 12, 8 and 6 patients received a third, fourth and fifth dose respectively. Most patients received repeated doses prophylactically after a second. Median time to B cell repopulation after 1st dose was 208 days (149–479). A 6-month relapse free time was 86.7% in those not given a prophylactic dose. Adverse events were few.

Our data demonstrates that a single dose of 375mg/m² induces B cell depletion and maintains remission comparable to larger doses. A lower dose has cost-effective benefits but may also reduce the risk of long-term adverse effects. Further work is needed to optimize treatment strategies for repeated rituximab dosing.