A 32-year-old woman from Delhi presents with progressive ankle swelling and facial puffiness for 3 weeks. She reports foamy urine and mild dyspnea on exertion. On examination: BP 128/82 mmHg, bilateral pitting ankle edema, no rash. Urinalysis shows 4+ proteinuria and lipiduria. Serum albumin 2.1 g/dL (normal 3.5–5.5), total cholesterol 320 mg/dL, serum creatinine 0.9 mg/dL. Renal ultrasound shows normal-sized kidneys with preserved echotexture. Anti-GBM antibody and ANCA are negative. What is the most likely diagnosis?

Explanation

## Clinical Presentation Analysis **Key Point:** The constellation of sudden-onset nephrotic syndrome (proteinuria >3.5 g/day, hypoalbuminemia, hyperlipidemia, edema) with normal renal function and preserved kidney architecture in a young adult female strongly suggests **Minimal Change Disease (MCD)**. ## Diagnostic Features Supporting MCD | Feature | MCD | FSGS | Membranous | MPGN | |---------|-----|------|-----------|------| | **Age of onset** | Children & young adults | Any age | 40–60 years | Variable | | **Proteinuria** | Selective (mainly albumin) | Non-selective | Non-selective | Non-selective | | **Renal function** | Preserved (early) | Often impaired | Slowly progressive | Progressive | | **Serum creatinine** | Normal | Often ↑ | Normal initially | Often ↑ | | **Kidney ultrasound** | Normal | Normal | Normal | Normal | | **Immunology** | Negative | Negative | IgG/IgM deposits | C3 dominant | | **Response to steroids** | 90% remission | Poor | Poor | Poor | **High-Yield:** MCD accounts for ~90% of nephrotic syndrome in children and 10–15% in adults. The **selective proteinuria** (mainly albumin) and **preserved renal function** are hallmark features. ## Why This Case Points to MCD 1. **Young female** — MCD has a second peak in young adulthood after childhood 2. **Acute onset** — typical presentation is sudden (weeks) 3. **Normal renal function** — serum creatinine 0.9 mg/dL rules out advanced glomerulonephritis 4. **Normal kidney ultrasound** — excludes structural disease 5. **Negative autoimmune markers** (anti-GBM, ANCA) — rules out vasculitis-associated GN 6. **Lipiduria** — indicates selective proteinuria (albumin loss → lipid loss) **Clinical Pearl:** MCD is a **podocyte dysfunction disease** (not immune-mediated) characterized by foot process effacement on electron microscopy. It is **steroid-responsive** in >90% of cases, making empirical corticosteroid therapy justified after ruling out secondary causes. ## Differential Diagnosis Exclusion - **Membranous nephropathy:** Typically presents in older adults (40–60 years); more insidious onset; higher risk of thromboembolism - **FSGS:** Often presents with impaired renal function; less likely to achieve complete remission; steroid-resistant in many cases - **MPGN:** Usually associated with systemic disease (hepatitis C, lupus) or positive serology; progressive renal dysfunction is more common **Mnemonic:** **MCD = "Most Common in Children, Dramatic response to steroids"** — Remember: young age + sudden onset + normal creatinine + negative serology = think MCD first.