A 32-year-old woman from Delhi presents with nephrotic syndrome (proteinuria 8 g/day, serum albumin 2.1 g/dL, edema). Serum creatinine is 0.9 mg/dL and urinalysis shows selective proteinuria with no RBC casts. Complement levels are normal. Renal ultrasound is normal. What is the most appropriate next step in management?

Explanation

## Clinical Context This 32-year-old woman presents with **nephrotic syndrome** (proteinuria 8 g/day, hypoalbuminemia, edema) with preserved renal function, normal complement levels, selective proteinuria, and no RBC casts. ## Why Renal Biopsy Is the Most Appropriate Next Step **Key Point:** In **adults** (≥16–18 years) presenting with nephrotic syndrome, renal biopsy is the standard of care before initiating immunosuppressive therapy, regardless of how "classic" the presentation appears. **High-Yield:** Unlike children (where MCD accounts for ~90% of nephrotic syndrome and empirical steroids are justified), adults have a much broader differential: - **Focal Segmental Glomerulosclerosis (FSGS):** ~35% of adult nephrotic syndrome — requires steroids but at different protocols; steroid resistance is common - **Membranous Nephropathy:** ~30% — requires specific immunosuppression (rituximab, cyclophosphamide-based regimens); steroids alone are insufficient - **Minimal Change Disease (MCD):** ~15–25% in adults — responds to steroids - **IgA Nephropathy / Mesangial proliferative GN:** variable treatment ### Why Empirical Steroids Are Inappropriate in Adults | Feature | Children | Adults | |---------|----------|--------| | MCD prevalence | ~90% | ~15–25% | | Empirical steroids | Justified | NOT standard of care | | Biopsy before treatment | Not mandatory | **Mandatory** | | Differential diagnosis | Narrow | Broad | **Clinical Pearl (Harrison's Principles of Internal Medicine):** In adults with nephrotic syndrome, renal biopsy is essential to establish the histopathological diagnosis, guide specific therapy, and determine prognosis. Empirical steroid therapy without biopsy risks undertreating membranous nephropathy or FSGS and may cause unnecessary steroid toxicity if the underlying disease is not steroid-responsive. ## Indications for Biopsy in Nephrotic Syndrome - **All adults** with new-onset nephrotic syndrome (standard practice per KDIGO guidelines) - Steroid-resistant nephrotic syndrome in children - Atypical features at any age (hematuria, low complement, elevated creatinine) - Suspicion of secondary causes (lupus, amyloidosis, diabetic nephropathy) ## Why Other Options Are Incorrect - **A) Empirical corticosteroids:** Appropriate in children with classic MCD features; NOT appropriate in adults where biopsy is mandatory first - **C) ACE inhibitor monotherapy:** Useful as adjunctive antiproteinuric therapy but not definitive management without a diagnosis - **D) Cyclophosphamide pulse therapy:** Reserved for specific histological diagnoses (e.g., membranous nephropathy, FSGS); premature without biopsy **Reference:** KDIGO Clinical Practice Guideline for Glomerulonephritis (2012); Harrison's Principles of Internal Medicine, 21st ed., Chapter on Glomerular Diseases.