Describe clinical manifestation and management of nephrotic syndrome due to glomerulonephritis. minimal change.
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"minimal change disease" AND "nephrotic syndrome" AND management
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Nephrotic Syndrome Due to Minimal Change Disease (MCD)
Glomerular schematic of MCD - note the structurally normal-appearing glomerulus on light microscopy, with the characteristic foot process effacement only visible on electron microscopy. (Harrison's Principles of Internal Medicine, 22e)
Overview & Epidemiology
Minimal change disease (MCD) - historically called "lipoid nephrosis" (Munk, 1913) or "nil lesion" - is the leading cause of nephrotic syndrome in the pediatric population and a significant cause in adults:
- Children under 10 years: 70-90% of nephrotic syndrome cases
- Adults: 10-15% of primary nephrotic syndrome
- Geographic variation: higher incidence in Asia than North America/Europe
- Slight male predominance (M:F ratio ~1.1:1 in adults)
(Brenner and Rector's The Kidney, 2-Volume Set; Harrison's Principles of Internal Medicine 22e)
Pathogenesis
The exact mechanism is incompletely understood but immune dysregulation - particularly of T cells - is the central hypothesis:
- T cell dysfunction: T cell hybridomas from MCD patients secrete a circulating factor that induces heavy proteinuria in animal models. Disturbances in T-cell response result in circulating glomerular permeability factors (proposed cytokines: IL-13 and IL-4)
- CD80 (B7.1) overexpression: Elevated CD80 on podocytes correlates with disease activity and promotes dysregulated interactions with T lymphocytes via CTLA-4
- Angiopoietin-like-4: Overexpressed in MCD podocytes, promoting proteinuria; this is suppressible with corticosteroids
- Anti-nephrin antibodies: A subset of patients have antibodies to nephrin despite minimal IgG on immunofluorescence - suggesting a B cell component
- Glomerular endothelial injury: Evidence of mild endothelial injury with circulating biomarkers suggests MCD is not a pure "podocytopathy"
- Secondary causes: NSAID use, lithium, Hodgkin lymphoma, thymoma, allergies, infections
(Comprehensive Clinical Nephrology, 7th Edition; Harrison's 22e)
Histopathology
The triad of findings across microscopy modalities:
| Modality | Finding |
|---|---|
| Light microscopy | Normal (minimal/absent changes) - hence the name |
| Immunofluorescence | Negative; occasionally small amounts of IgM in mesangium |
| Electron microscopy | Extensive diffuse foot process effacement (fusion) - the diagnostic hallmark |
(NKF Primer on Kidney Diseases, 8e; Harrison's 22e)
Clinical Manifestations
Core Nephrotic Syndrome Features
- Massive proteinuria: Mean 24-hour urine protein ~10 g (selective proteinuria in children - predominantly albumin with minimal higher-molecular-weight proteins)
- Severe hypoalbuminemia
- Edema: Characteristically abrupt onset; can be severe (anasarca, periorbital edema - especially in children, ascites, pleural effusions)
- Hyperlipidemia and lipiduria (lipoid nephrosis)
Less Common Features
| Feature | Children | Adults |
|---|---|---|
| Hypertension | ~30% | 20-50% |
| Microscopic hematuria | ~20% | ~33% |
| Atopy/allergic symptoms | ~40% | ~30% |
| Reduced kidney function | 25-40% (often reversible) | similar |
Acute Kidney Injury in MCD
- Occurs more commonly in adults with very low serum albumin and intrarenal edema ("nephrosarca")
- Often responsive to diuretics
- Must be distinguished from AKI due to hypovolemia - the two have opposite treatments
- Acute tubular necrosis and interstitial inflammation can also occur
Salt and Water Retention Mechanisms
In most adults, the expanded plasma volume results from primary salt retention: increased GBM permeability allows filtration of circulating proteases which activate ENaC in the collecting tubule, promoting sodium reabsorption independently of aldosterone. In a minority (mostly children), oncotic pressure-driven intravascular depletion activates the RAAS.
(Harrison's 22e; Goldman-Cecil Medicine)
Diagnosis
- Children: In the setting of classic nephrotic syndrome without hematuria, reduced GFR, hypertension, or low complement - MCD is diagnosed presumptively and treated empirically. Kidney biopsy is generally not required in children.
- Adults: Kidney biopsy is mandatory as many other diagnoses (FSGS, membranous nephropathy) can present identically
Factors Suggesting Diagnosis Other Than Idiopathic MCD (Harriet Lane Handbook)
- Hematuria
- Hypertension
- Low complement levels
- Reduced GFR not responsive to therapy
- Steroid resistance
Management
General Supportive Care (all patients)
| Issue | Treatment |
|---|---|
| Edema | Loop diuretics; avoid over-diuresis causing hypovolemia |
| Proteinuria/hypertension | ACE inhibitor or ARB |
| Hyperlipidemia | Statins (mainly adults; children often reach remission before treatment needed) |
| Thrombosis prevention | Anticoagulation if serum albumin <2 g/dL (low-molecular-weight heparin or warfarin); switch to aspirin once albumin >2 g/dL |
| Diet | Low-salt, protein-restricted (0.8-1 g/kg/day) |
| AKI | Supportive; repeat biopsy if persistent |
(NKF Primer 8e; Comprehensive Clinical Nephrology 7e)
Immunosuppressive Therapy
First-Line: Corticosteroids
In children (ISKDC protocol):
- Prednisone 60 mg/m²/day (max 60 mg/day) for 4-6 weeks, then 40 mg/m² on alternate days for 4-6 weeks, then taper
- ~95% of children with MCD respond to steroids
- ~30% have spontaneous remission; most today are treated empirically before biopsy
In adults:
- Prednisone 1 mg/kg/day (max 80 mg/day) for 4-16 weeks until remission, then slow taper
- Response rates are 80-90% but take longer than children
Definitions of response (Comprehensive Clinical Nephrology 7e):
| Term | Definition |
|---|---|
| Complete remission (CR) | uPCR <0.2 mg/mg (children) / proteinuria ≤0.20 g/day + albumin ≥3.5 g/dL (adults) |
| Partial remission (PR) | 50% reduction in proteinuria + uPCR 0.2-2 mg/mg |
| Relapse | Recurrence of nephrotic-range proteinuria after CR for >1 month |
| SSNS | Steroid-sensitive nephrotic syndrome - CR within 4 weeks |
| FRNS | Frequently relapsing: ≥2 relapses per 6 months or ≥4 per 12 months |
| SDNS | Steroid-dependent: relapse during or within 15 days of stopping steroids |
| SRNS | Steroid-resistant: no CR after 4 weeks full-dose prednisone |
Relapse Management and Steroid-Sparing Therapies
Relapses occur in 70-75% of children after first remission; early relapse predicts future relapses. Relapses are less frequent in adults but more resistant to subsequent treatment.
Calcineurin Inhibitors (CNIs):
- Cyclosporine: 4-6 mg/kg/day, trough levels 150-200 ng/mL
- Tacrolimus (preferred due to side effect profile): 0.05-0.1 mg/kg/day, trough 4-8 ng/mL
- Induce remission in up to 75% of patients
- Relapse is common upon dose reduction; KDIGO recommends 1-2 years of therapy
- Tacrolimus is safe in pregnancy and breastfeeding - preferred in young women
Cyclophosphamide:
- Oral cyclophosphamide 2-2.5 mg/kg/day for 12 weeks (children: 8 weeks)
- Induces longer-term remission: 75% at 2 years and 66% at 5 years in adults
- May be preferred in older adults where fertility preservation is not a concern
- Can be used as initial therapy where steroids are contraindicated
Mycophenolate Mofetil (MMF):
- Used as steroid-sparing agent
- MMF + low-dose prednisolone showed similar efficacy to high-dose prednisolone alone in adults
- Option for FRNS and SDNS
Rituximab (anti-CD20):
- Increasingly used for FRNS, SDNS, and SRNS
- Median time to relapse after rituximab: ~18 months
- Six-monthly maintenance dosing effective for frequent relapsers
- Can be used as first-line therapy in patients with contraindications to steroids
- Note: protein-binding means enhanced dosing may be needed when patients are nephrotic
- Monitor for hypogammaglobulinemia
- Generally well tolerated in both children and adults
(Comprehensive Clinical Nephrology 7e; Harrison's 22e; NKF Primer 8e)
Prognosis
- Children have an excellent long-term renal prognosis despite frequent relapses; relapse frequency decreases after puberty
- Adults have a less favorable prognosis when acute kidney failure or steroid resistance is present
- Complete recovery of renal function is the norm after remission in most patients
- MCD very rarely progresses to ESKD in steroid-responsive disease
Key Sources
- Harrison's Principles of Internal Medicine, 22e (2025), Chapter 326
- Comprehensive Clinical Nephrology, 7th Edition, Chapter 18
- NKF Primer on Kidney Diseases, 8th Edition, Chapter 16/18
- Brenner and Rector's The Kidney, 2-Volume Set, Chapter 31
- Goldman-Cecil Medicine (International Edition)
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