✅ Model Answer:
• Diagnosis: Acute poststreptococcal glomerulonephritis (APSGN).
• Evidence: Elevated ASO Titer, low C3 Complement, Latency 1-2 weeks post-strep, gross hematuria with RBC casts, hypertension, edema, low C3 (classic pathway), normal C4, elevated ASO titer.
• Next step: Monitor BP, fluid/salt restriction, furosemide if edema, treat hypertension (amlodipine or nifedipine). C3 normalizes in 8-10 weeks. Throat swab for culture and antibiotic if ongoing strep infection.

✅ Model Answer:
• Causative organism: Group A beta-hemolytic streptococcus (GAS) – most commonly pharyngitis or skin infection (impetigo).
• Latency: 1-2 weeks after pharyngitis; 3-4 weeks after skin infection.
• Pathogenesis: Immune-complex mediated glomerulonephritis. Circulating immune complexes (antigen-antibody) deposit in the glomerular basement membrane → complement activation (C3) → inflammation → glomerular injury.
• Complement: Low C3, normal C4 (classical pathway activation). C3 returns to normal in 8-10 weeks.
• Histology: Diffuse proliferative glomerulonephritis with subepithelial "humps" (electron-dense deposits) on electron microscopy.

✅ Model Answer:
• Classic triad: Hematuria (gross or microscopic), edema (periorbital, dependent), hypertension.
• Other features: Oliguria, proteinuria (subnephrotic), fatigue, flank pain, fever (low-grade).
• Latency: 1-2 weeks after pharyngitis; 3-4 weeks after skin infection.
• Age: Most common in children 5-12 years.
• Complications: Hypertensive encephalopathy, heart failure, pulmonary edema, acute kidney injury (AKI), rapidly progressive glomerulonephritis (RPGN – rare).

✅ Model Answer:
• Urinalysis: Gross or microscopic hematuria, RBC casts (>1-2 per HPF), proteinuria (usually 2+), pyuria.
• Serum studies:
- C3 complement: Low (decreases in acute phase, normalizes in 8-10 weeks).
- C4 complement: Normal (differentiates from lupus nephritis).
- ASO titer: Elevated (evidence of recent strep infection).
- Anti-DNase B: Also elevated (especially after skin infections).
- Serum creatinine: May be elevated (acute kidney injury).
• Throat swab culture: For strep (may be negative if infection resolved).
• Blood pressure monitoring.
• Renal biopsy: Indicated if atypical features (nephrotic-range proteinuria, persistent low C3 >8 weeks, rapidly worsening renal function).

✅ Model Answer:
• Supportive care:
- Fluid restriction: If edema or hypertension (daily fluid = insensible losses + urine output).
- Salt restriction: Low sodium diet (<2 g/day).
- Diuretics: Furosemide 1-2 mg/kg IV/PO for edema and hypertension.
- Antihypertensives: Amlodipine (0.1-0.2 mg/kg/day) or nifedipine (0.25-0.5 mg/kg) for severe hypertension. Avoid ACE inhibitors in acute phase (risk of hyperkalemia and AKI).
- Antibiotics: If ongoing strep infection – penicillin V 250-500 mg PO q6h for 10 days.
• Dialysis: If severe AKI (hyperkalemia, acidosis, uremia, fluid overload).
• Monitor: Blood pressure, urine output, creatinine, potassium, C3 (normalizes in 8-10 weeks).

✅ Model Answer:
• Hypertensive encephalopathy: Headache, confusion, seizures, visual disturbances – treat with rapid BP control (nifedipine, labetalol).
• Congestive heart failure: Due to fluid overload – treat with furosemide and fluid restriction.
• Pulmonary edema: Dyspnea, hypoxia – requires dialysis if severe.
• Acute kidney injury (AKI): Oliguria, rising creatinine – may require dialysis.
• Hyperkalemia: Monitor potassium (avoid ACE inhibitors, potassium-sparing diuretics).
• Rapidly progressive glomerulonephritis (RPGN): Rare (<5%) – requires pulse steroids and cyclophosphamide.
• Chronic kidney disease: Uncommon in children (prognosis is excellent).

✅ Model Answer:
• Prognosis:
- Excellent in children (95% recover fully).
- Clinical recovery: Edema and hypertension resolve in 1-2 weeks; proteinuria resolves in 3-6 months; microscopic hematuria may persist for 1-2 years.
- C3 normalizes: In 8-10 weeks (if C3 remains low >8 weeks, suspect other causes like MPGN or lupus).
- Adults: Worse prognosis (20-30% develop chronic kidney disease).
• Long-term follow-up:
- Monitor BP: Annually (risk of late hypertension).
- Urinalysis: Check proteinuria and hematuria at 6 months, 1 year, and then annually.
- Creatinine: Monitor renal function.
- No special diet: After recovery.
- Vaccination: No specific vaccines; treat future strep infections promptly.

✅ Model Answer:
• APSGN:
- Timing: Latency 1-2 weeks after infection.
- C3: Low.
- C4: Normal.
- ASO: Elevated.
- RBC casts: Present.
- Hypertension/Edema: Common.
- Biopsy: Subepithelial "humps."
- Prognosis: Excellent in children.
• IgA nephropathy:
- Timing: 1-2 days after URI (synpharyngitic).
- C3: Normal.
- C4: Normal.
- ASO: Normal.
- RBC casts: Absent (usually).
- Hypertension/Edema: Less common (usually well).
- Biopsy: Mesangial IgA deposits.
- Prognosis: Variable; 30-40% progress to CKD.