How should I treat a 19-year-old woman with childhood-onset steroid-dependent nephrotic syndrome who has failed cyclophosphamide, mycophenolate mofetil, and tacrolimus?

Treatment Recommendation for Multi-Drug Resistant Steroid-Dependent Nephrotic Syndrome

Rituximab is the treatment of choice for this 19-year-old woman with childhood-onset steroid-dependent nephrotic syndrome who has failed cyclophosphamide, MMF, and tacrolimus. 1

Rationale and Evidence Base

The 2025 KDIGO guidelines explicitly address this clinical scenario. For steroid-dependent nephrotic syndrome, the guideline states that "mycophenolate mofetil, rituximab, calcineurin inhibitor, and, to a lesser extent, oral cyclophosphamide may be preferable" 1. However, since this patient has already failed cyclophosphamide, MMF, and tacrolimus (a calcineurin inhibitor), rituximab emerges as the logical next-line agent.

Why Rituximab?

• Efficacy in refractory cases: The 2025 KDIGO guidelines specifically note that "in children with complicated forms of frequently relapsing or corticosteroid-dependent nephrotic syndrome, the use of mycophenolate mofetil after rituximab can decrease the risk of treatment failure" 1. This suggests rituximab's role as a backbone therapy in difficult cases.

• Evidence in multi-drug resistant patients: Recent systematic review data (2024) demonstrates that rituximab achieves an 89% complete remission rate (95% CI: 83-94%) in adult steroid-dependent/frequently relapsing nephrotic syndrome, which is superior to all other agents studied 2. While this is low certainty evidence with heterogeneity, it represents the best available data for refractory cases.

• Acceptable safety profile: The adverse event rate with rituximab is 0.26, which is reasonable given the severity of this patient's disease and steroid toxicity burden 2.

Practical Implementation

Dosing approach: Current trials report administration of 1-4 doses of rituximab, though KDIGO acknowledges "there are insufficient data to make a specific recommendation" on optimal dosing 1. In clinical practice, a common regimen is:

• 375 mg/m² weekly for 2-4 doses, OR
• Two doses of 750 mg/m² given 2 weeks apart

Steroid management during transition: The patient should ideally be in remission with glucocorticoids prior to initiating rituximab, with continuation of glucocorticoids for 2 weeks following rituximab initiation 1.

Post-rituximab maintenance: Consider adding MMF after rituximab therapy, as the 2025 KDIGO guidelines specifically state this combination "can decrease the risk of treatment failure" in complicated cases 1. This is particularly relevant since she has already been exposed to MMF—reintroducing it after rituximab-induced B-cell depletion may yield different results 3.

Important Caveats

Rule Out Steroid-Resistant Nephrotic Syndrome

At 19 years old with childhood onset disease that has failed multiple agents, ensure this is truly steroid-dependent and not steroid-resistant nephrotic syndrome (SRNS). If she has developed steroid resistance:

• The 2025 KDIGO guidelines note that "rituximab may be helpful in attaining remission in ~30% of children with calcineurin inhibitor-resistant SRNS" 1
• This is a lower response rate than in steroid-dependent disease, but still represents a viable option
• Consider genetic testing if not already performed, as this influences prognosis and may guide alternative approaches

Monitor for Relapse Pattern

Watch for early relapse after rituximab: Some patients have a short serum half-life following recovery of CD20-positive cells 3. If she relapses quickly after rituximab:

• Consider re-dosing rituximab based on CD19/CD20 B-cell monitoring
• Add MMF as maintenance therapy to extend the duration of remission 3

Alternative if Rituximab Fails or is Unavailable

If rituximab is not accessible or fails, consider switching between calcineurin inhibitors (cyclosporine if she was on tacrolimus, or vice versa), though evidence for this approach is limited. The 2019 study showing tacrolimus can induce remission in cyclosporine-resistant cases suggests some patients respond differently to different CNIs 4.

Address Steroid Toxicity Aggressively

Given her long disease course from childhood, she likely has significant glucocorticoid toxicity. Implement robust steroid-sparing approaches with shorter tapers once remission is achieved 1. The goal is to minimize cumulative steroid exposure while maintaining remission with rituximab ± MMF.

What NOT to Do

• Do not retry cyclophosphamide: She has already failed this agent, and cumulative alkylating agent exposure increases malignancy and infertility risks
• Do not continue tacrolimus monotherapy: It has clearly failed in her case
• Do not use levamisole: While mentioned in guidelines for frequently relapsing disease, it is less appropriate for steroid-dependent disease and is unavailable in many countries 5