Objective  To explore the efficacy and safety of single small-dose rituximab for idiopathic membranous nephropathy （IMN） and examine the difference with conventional-dose therapy.

Methods  From December 2019 to November 2022, retrospective analysis was conducted for 25 IMN patients at Department of Nephrology, Guanggu Hospital, Hubei Provincial Hospital of Traditional Chinese Medicine. A definite diagnosis of IMN was made by renal puncture pathology and detection of positive anti-phospholipase A2 receptor antibody and using rituximab （RTX）. An overall dose of 2,000 mg RTX was offered on the basis of basic supportive treatment. The once weekly dose was 200 mg in single small-dose group （n=15） versus 500 mg in conventional-dose group （n=10）. The relevant laboratory parameters of two groups were compared at pre-treatment with those at Month 3/6 post-treatment.

Results  At Month 3, overall remission rate was 33% in single small-dose group versus 60% in conventional-dose group and the inter-group difference was not statistically significant （P＞0.05）; at Month 6, overall remission rate was 40% in single small-dose group versus 70% in conventional-dose group and the inter-group difference was not statistically significant （P＞0.05）. At Months 3 and 6, quantitative 24 h urine protein was （3.42 ± 2.59）g vs （1.96 ± 3.25） g, blood albumin （26.40 ± 9.90） g/L vs （40.35 ± 5.06） g/L, hemoglobin （120.00 ± 13.30） g/L vs （130.60 ± 19.10） g/L, CD19⁺B lymphocyte （6.33 ± 5.50） cells/μL vs （2.67 ± 9.25） cells/μL, proportion of CD19⁺B lymphocyte count ＜5/μL （n=7 vs n=13）, negativity rate of anti-phospholipase A2 receptor antibody （n=12 vs n=14）, erythrocyte sedimentation rate （48.93 ± 25.89） mm/h vs （38.13 ± 31.03） mm/h, total cholesterol （5.27 ± 1.59） mmol/L vs （4.67 ± 1.49） mmol/L, low-density lipoprotein （2.80 ± 1.59） mmol/Lvs （4.67 ± 1.49） mmol/L and D-2 dimer （0.36 ± 0.29） mg/L vs （0.11 ± 0.15） mg/L were statistically different from those pre-treatment （P＜0.05）. In conventional-dose group, 24 h urine protein quantification was （3.20 ± 3.5）g vs （1.06 ± 1.14） g, blood albumin （32.10 ± 8.00） g/L vs （36.26 ± 4.34） g/L, hemoglobin （129.60 ± 15.70） g/L vs （134.70 ± 10.99） g/L, CD19⁺B lymphocyte （5.50 ± 4.74） cells/μL vs （2.30 ± 6.25） cells/μL, proportion of CD19⁺B lymphocyte count ＜5/μL （n=9 vs n=9） and negativity rate of anti-phospholipase A2 receptor antibody （n=7 vs n=10） were statistically significant from those pre-treatment （P＜0.05）; At Month 3, serum immunoglobulin G was （3.13 ± 0.68） g/L and high-density lipoprotein （0.58 ± 0.64） mmol/L. Both were statistically significant from those pre-treatment （P＞0.05）. When comparing single small-dose and conventional-dose groups at Month 3, serum immunoglobulin G was （5.59 ± 2.48） g/L vs （3.13 ± 0.68） g/L, interleukin 6 （2.02 ± 1.65） ng/L vs （5.85 ± 5.09） ng/L and high-density lipoprotein （1.15 ± 0.42） mmol/L vs （0.58 ± 0.64） mmol/L were statistically significant between two groups （P＜0.05）. No statistically significant inter-group differences existed in the ratio of helper T-cells to suppressor T-cells or ultrasensitive C-reactive protein （CRP） at pre/post-treatment （P＞0.05）. During treatment, the incidence of adverse events was lower in single small-dose group than that in conventional-dose group （13.33% vs 50%）. And the inter-group difference was statistically significant （P＜0.05）.

Conclusion  A single small-dose RTX has significant clearance of CD19⁺B lymphocytes, improvement of negativity rate of anti-phospholipase A2 receptor antibody （anti-phospholipase A2 receptor antibody） and promotion of remission in IMN patients. Its efficacy is not significantly different from that of conventional-dose RTX. However, the incidence of adverse events is lower and the safety is better.