Renal · Year 2 · from Renal

Case 1: Minimal Change Disease

Patient Presentation

Demographics: 5-year-old male

Chief Complaint: Facial and leg swelling for 1 week

History of Present Illness: The patient's mother noticed swelling around his eyes 1 week ago, which has progressed to include his legs and abdomen. She reports he has been urinating less frequently and the urine appears "foamy." He had an upper respiratory infection 2 weeks ago that resolved. He has no history of similar episodes.

Physical Examination:

  • Blood pressure: 100/60 mmHg (normal for age)
  • Weight: 22 kg (up from 18 kg at last visit)
  • General: Well-appearing but edematous
  • HEENT: Periorbital edema
  • Lungs: Clear
  • Abdomen: Distended with shifting dullness (ascites)
  • Extremities: 3+ pitting edema
  • Skin: No rashes

Workup and Results

Laboratory Studies:

  • Creatinine: 0.4 mg/dL (normal)
  • BUN: 12 mg/dL
  • Albumin: 1.4 g/dL (low)
  • Total cholesterol: 380 mg/dL (elevated)
  • Urinalysis: 4+ protein, no blood, oval fat bodies
  • Spot urine protein-to-creatinine ratio: 12 mg/mg (nephrotic range)
  • C3 and C4: Normal

Clinical Image

Electron microscopy of minimal change disease demonstrating diffuse podocyte foot process effacement with otherwise normal glomerular basement membrane and no immune deposits.

Diagnosis

Nephrotic Syndrome due to Minimal Change Disease

Features supporting this diagnosis:

  • Age (most common cause in children)
  • Nephrotic-range proteinuria (>3.5 g/day equivalent)
  • Hypoalbuminemia and hyperlipidemia
  • Bland urine sediment (no hematuria)
  • Normal complement levels

Discussion

This case illustrates classic minimal change disease:

  • Most Common in Children: The lecture notes MCD is the most common cause of nephrotic syndrome in children, accounting for 70-90% of cases under age 10.
  • Nephrotic Syndrome Definition: Proteinuria >3.5 g/day (or equivalent ratio in children), hypoalbuminemia, hyperlipidemia, and edema. The lecture emphasizes that nephrotic-range proteinuria is the defining feature.
  • Pathophysiology: T-cell dysfunction leads to circulating factors that damage podocytes. Light microscopy shows normal-appearing glomeruli; electron microscopy reveals diffuse foot process effacement.
  • Excellent Steroid Response: The lecture states that 90% of patients achieve complete remission with corticosteroids, distinguishing MCD from other causes.

Treatment Plan

  1. First-line Therapy:
  • Prednisone 60 mg/m2/day (max 60 mg) for 4-6 weeks
  • Then alternate-day dosing and taper
  1. Supportive Care:
  • Sodium restriction (<2 g/day)
  • Careful diuretic use for severe edema (furosemide with albumin)
  • No fluid restriction unless symptomatic
  1. Monitoring:
  • Daily urine dipstick for protein
  • Weekly weights
  • Watch for complications (infection, thrombosis)
  1. Expected Response:
  • Complete remission (negative protein) expected within 4 weeks
  • 70-80% relapse, often with intercurrent illness

Teaching Points

  1. Minimal change disease shows normal light microscopy but diffuse foot process effacement on EM
  2. Children with first-episode nephrotic syndrome receive empiric steroids without biopsy
  3. Nephrotic syndrome increases infection risk (immunoglobulin loss) and thrombosis risk

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