What are the causes of nephrotic syndrome in a 15-year-old and how should it be managed?

Nephrotic Syndrome in a 15-Year-Old: Causes and Management

In a 15-year-old with nephrotic syndrome, minimal change disease remains the most common cause, and you should initiate oral glucocorticoids (prednisone/prednisolone) at 60 mg/m²/day for 4-6 weeks followed by 40 mg/m² on alternate days for 6-8 weeks as first-line therapy 1, 2.

Primary Causes at Age 15

At 15 years old, this patient sits at the transition between pediatric and adult patterns:

• Minimal change disease remains the predominant cause in this age group, though less common than in younger children 3, 4
• Focal segmental glomerulosclerosis (FSGS) increases in frequency with age
• Secondary causes become more relevant: consider lupus nephritis (SLE), drug-induced (NSAIDs), and malignancy-associated nephrotic syndrome 2

A kidney biopsy is essential for definitive diagnosis in adolescents and adults - you cannot assume minimal change disease without histologic confirmation at this age 2.

Initial Management Algorithm

Step 1: Confirm Diagnosis and Initiate Treatment

Start glucocorticoids immediately after biopsy (or empirically if biopsy delayed):

• Prednisone 60 mg/m²/day (max 60-80 mg/day) for 4-6 weeks daily
• Then 40 mg/m² on alternate days for 6-8 weeks
• Total duration: 8-12 weeks for initial episode 1, 4

The KDIGO 2025 guideline specifically recommends either an 8-week regimen (4 weeks daily + 4 weeks alternate-day) or 12-week regimen (6 weeks daily + 6 weeks alternate-day) 1.

Step 2: Classify Based on Steroid Response

Steroid-sensitive nephrotic syndrome (SSNS):

• Achieves complete remission with glucocorticoids
• Excellent long-term kidney survival 2
• Monitor for relapse pattern

Steroid-resistant nephrotic syndrome (SRNS):

• No remission after 8-12 weeks of glucocorticoids
• Immediately initiate cyclosporine or tacrolimus as second-line therapy 1, 2
• Order genetic testing in parallel - 11-30% have monogenic causes that won't respond to immunosuppression 2

Step 3: Manage Relapsing Disease

Frequently relapsing nephrotic syndrome (≥4 relapses in 12 months):

• Do NOT routinely give daily glucocorticoids during upper respiratory infections - the PREDNOS2 study showed no benefit 1
• For relapses without glucocorticoid toxicity: use standard glucocorticoid regimen for each relapse, consider low-dose alternate-day prednisone for prevention 1

Steroid-dependent nephrotic syndrome or frequently relapsing with serious steroid toxicity:

• Mandatory use of glucocorticoid-sparing agents 1, 2
• The 2025 guideline removes the distinction between "first-line" and "alternative" agents

Preferred glucocorticoid-sparing agents by pattern:

• Frequently relapsing: Oral cyclophosphamide or levamisole preferred 1
• Steroid-dependent: Mycophenolate mofetil, rituximab, calcineurin inhibitors (cyclosporine/tacrolimus), or cyclophosphamide 1
• Complicated cases: Consider mycophenolate mofetil after rituximab to decrease treatment failure risk 1

Step 4: Steroid-Resistant Disease Management

For SRNS, use cyclosporine or tacrolimus as initial second-line therapy 1, 2:

• No head-to-head trials comparing the two
• Cyclosporine: more gingival hypertrophy and hirsutism
• Tacrolimus: more glucose intolerance/diabetes
• Both require drug-level monitoring (trough levels before morning/evening doses)
• Both carry risk of nephrotoxicity with long-term use 2

If calcineurin inhibitor-resistant:

• Rituximab achieves remission in ~30% of children with CNI-resistant SRNS 1
• Mycophenolate mofetil has very limited evidence 1

Critical Monitoring and Complications

Home monitoring is essential:

• Train patient/family to check urine protein daily with dipsticks
• Maintain detailed medication records 5
• Note: Lack of insurance coverage for urine dipsticks in the US is a significant barrier 6

Watch for serious complications:

• Infections (due to immunosuppression and hypogammaglobulinemia)
• Thromboembolism (hypercoagulable state from urinary losses)
• Acute kidney injury (from hypovolemia or drug toxicity)
• Severe edema requiring diuretics 5

Monitor for glucocorticoid toxicity:

• Growth failure, obesity, hypertension, diabetes, osteoporosis, behavioral changes, cataracts
• Majority of frequently relapsing patients develop ≥1 severe steroid side effect 2
• This mandates earlier use of steroid-sparing agents

Common Pitfalls

1. Delaying biopsy in adolescents - don't assume minimal change disease at age 15
2. Treating infections prophylactically with steroids - PREDNOS2 proved this ineffective 1
3. Continuing glucocorticoids alone in frequently relapsing/steroid-dependent disease - this causes unacceptable toxicity; switch to steroid-sparing agents 1
4. Not testing for genetic causes in SRNS - 11-30% have monogenic disease that won't respond to immunosuppression 2
5. Inadequate duration of initial glucocorticoid therapy - must complete full 8-12 weeks to properly classify steroid responsiveness 1

Long-term Prognosis

• Steroid-sensitive disease: Excellent long-term kidney survival, though many continue relapsing into adulthood 2, 5
• Steroid-resistant disease: High risk of progression to end-stage kidney disease, especially if multidrug resistant 5
• Co-management with pediatric nephrology is mandatory for all but the most straightforward steroid-sensitive cases 5