Source / episode info
- **Episode:**140
- **Title:**Divine Intervention Episode 140 – ABIM/Medicine ITE/USMLE Step 3 Review Series 10 (Nephro 2)
- **Published:**2019-08-23
- Source:Episode page
One-liner
This episode reviews the differential diagnosis of glomerulonephritis by classifying syndromes based on loss of complement regulatory proteins CD55/CD59 -> complement-mediated intravascular hemolysis (low vs. normal), focusing on key associations like IgA nephropathy's normal complement and mixed cryoglobulinemia's unique C4 depletion pattern.
High-yield summary
- Nephritic Syndrome: Characterized by inflammation of the glomerular capillaries, leading to hematuria, RBC casts, and hypertension (e.g., Post-infectious GN). Proteinuria is typically < 3.5 g/day.
- Nephrotic Syndrome: Defined by massive proteinuria (> 3.5 g/24h), hypoalbuminemia, edema, and lipid/fatty casts. Damage primarily affects the podocytes.
- IgA Nephropathy (Berger's Disease): The most common GN; classically presents with gross hematuria following an upper respiratory infection (URI) and has a characteristic triad of fever, rash, and hematuria. Crucially, complement levels are typically normal.
- Complement Patterns: Immune complex diseases often consume complement, leading to low C3/C4. Mixed cryoglobulinemia is unique for showing very low C4 but relatively preserved C3.
- Anti-GBM Syndrome: Characterized by antibodies targeting the basement membrane (e.g., anti-PR3 or anti-MPO). Diagnosis requires immunofluorescence testing and is associated with vasculitis syndromes like GPA/MPA.
Learning objectives
- Differentiate between the pathophysiology and clinical presentation of nephritic versus nephrotic syndromes.
- Identify the classic triad, associated antibodies, and complement levels for IgA nephropathy.
- Recognize the unique features (e.g., C4 depletion) of mixed cryoglobulinemia syndrome.
- Understand the diagnostic workup and management principles for anti-GBM vasculitis.
- Apply knowledge of immunosuppressive agents used in lupus nephritis flares, including drug interactions.
Board exam buzzwords