A 35-year-old woman with a 2-week history of gross hematuria, facial puffiness, and blood pressure of 156/98 mmHg is investigated for acute glomerulonephritis. Serum creatinine is 1.8 mg/dL (baseline 0.9 mg/dL), and urine shows dysmorphic RBCs with RBC casts. Serological workup reveals elevated anti-GBM antibodies. Which of the following is NOT consistent with the diagnosis of anti-GBM disease (Goodpasture syndrome)?

Explanation

## Anti-GBM Disease (Goodpasture Syndrome) — Nephritic vs. Nephrotic Presentation ### Pathophysiology and Clinical Presentation **Key Point:** Anti-GBM disease is a **rapidly progressive nephritic syndrome** characterized by acute glomerulonephritis with crescent formation, NOT a nephrotic syndrome. The dominant clinical feature is **rapidly declining renal function with hematuria**, not proteinuria or nephrotic features. ### Anti-GBM Disease: Nephritic, Not Nephrotic | Feature | Anti-GBM Disease | Nephrotic Syndrome | |---------|------------------|--------------------| | **Proteinuria** | Variable, often <3 g/day | >3.5 g/day (dominant) | | **Hematuria** | Dysmorphic RBCs, RBC casts (dominant) | Absent or mild | | **Hypertension** | Present (due to reduced GFR) | Variable | | **Edema** | Mild periorbital/facial | Generalized, severe | | **Serum albumin** | Normal or mildly low | Markedly low (<2.5 g/dL) | | **Lipiduria** | Absent | Present (oval fat bodies) | | **Renal function decline** | Rapid (days to weeks) | Slow (weeks to months) | **High-Yield:** Anti-GBM disease is a **rapidly progressive GN (RPGN)** with crescent formation, not a nephrotic disease. Even if proteinuria is present, it is NOT the dominant clinical feature — rapid renal failure and hematuria are. ### Correct Features of Anti-GBM Disease 1. **Rapid progressive glomerulonephritis with crescent formation** — ✓ Hallmark pathology; 80–90% have crescents on biopsy. 2. **Positive anti-GBM serology and linear IgG deposition** — ✓ Diagnostic; linear pattern on immunofluorescence is pathognomonic. 3. **Pulmonary hemorrhage** — ✓ Occurs in ~50% of cases (Goodpasture syndrome); presents with hemoptysis, dyspnea, and pulmonary infiltrates. ### Mnemonic: RPGN Causes **ANCA, Anti-GBM, Immune complex (lupus, PIGN)** - **A**NCA-associated (GPA, MPA, EGPA) - **A**nti-GBM (Goodpasture) - **I**mmune complex (lupus, PIGN, MPGN) ### Clinical Pearl **Why proteinuria is NOT the dominant feature in anti-GBM disease:** The pathology is primarily **glomerular necrosis and crescent formation** (destructive lesion), not glomerular permeability defect (as in membranous nephropathy). Therefore, hematuria and rapid GFR decline dominate; nephrotic features (hypoalbuminemia, lipiduria, severe proteinuria) are absent or minimal. [cite:Harrison 21e Ch 297; Robbins 10e Ch 20]