A 32-year-old woman with IgA nephropathy (confirmed on biopsy) presents with persistent hematuria, proteinuria of 2.5 g/day, and serum creatinine of 1.1 mg/dL. Blood pressure is 138/88 mmHg. She has no contraindications to ACE inhibitors. What is the drug of choice to slow progression of her renal disease and reduce proteinuria?

Explanation

## First-Line Renoprotective Agent in IgA Nephropathy ### Why ACE Inhibitor (Enalapril) is Preferred **Key Point:** ACE inhibitors are the first-line agents for slowing progression of IgA nephropathy and reducing proteinuria. They are superior to ARBs, calcium channel blockers, and aldosterone antagonists as monotherapy in patients without contraindications. **High-Yield:** In IgA nephropathy with proteinuria ≥1 g/day and preserved renal function, ACE inhibitors reduce proteinuria by 30–50% and slow the decline in GFR. This is the most robust evidence-based recommendation across major nephrology guidelines (KDIGO, ASN). **Clinical Pearl:** IgA nephropathy is the most common primary glomerulonephritis worldwide and often progresses insidiously. Early intervention with ACE inhibitors can prevent or delay progression to end-stage renal disease (ESRD), especially when combined with blood pressure control and lifestyle modification. ### Mechanism of Renoprotection in IgA Nephropathy ```mermaid flowchart TD A[IgA Nephropathy with Proteinuria]:::outcome --> B{Renal Protection Strategy}:::decision B -->|ACE Inhibitor| C[↓ Angiotensin II]:::action C --> D[↓ Efferent arteriolar vasoconstriction]:::action D --> E[↓ Intraglomerular pressure]:::action E --> F[↓ Proteinuria & ↓ GFR decline]:::outcome B -->|ARB| G[Similar mechanism to ACE-I]:::action B -->|CCB| H[Non-selective vasodilation]:::action H --> I[Less effective renal protection]:::outcome B -->|Aldosterone antagonist| J[Additive effect only]:::action ``` ### Comparison of Renoprotective Agents in IgA Nephropathy | Agent | Mechanism | Proteinuria Reduction | GFR Preservation | First-Line? | |-------|-----------|----------------------|------------------|-------------| | **ACE Inhibitor (Enalapril)** | ↓ Angiotensin II, ↓ efferent vasoconstriction | 30–50% | Excellent | **YES** | | ARB (Losartan) | ↓ Angiotensin II (AT1 receptor) | 25–40% | Good | No (second-line if ACE-I intolerant) | | Calcium channel blocker (Amlodipine) | Non-selective vasodilation | Minimal | Fair | No (add-on only for BP control) | | Aldosterone antagonist (Spironolactone) | ↓ Aldosterone | Modest (5–10%) | Modest | No (add-on only if residual proteinuria) | **Mnemonic:** **RAAS-I First** — In proteinuric glomerulonephritis, **RAAS Inhibitors (ACE-I or ARB) are First-line**. ACE-I is preferred if tolerated; ARB if ACE-I cough or angioedema occurs. **Tip:** Do NOT combine ACE inhibitor + ARB in routine practice (increased hyperkalemia and acute kidney injury risk without additional benefit). If proteinuria persists despite ACE-I monotherapy, add a calcium channel blocker or thiazide for blood pressure control, or consider spironolactone as an add-on (with careful potassium monitoring).