In a 33-year-old man with hemoptysis, oliguria for 48 hours, hypertension, hematuria with red blood cell casts, proteinuria, and a kidney biopsy showing linear immunofluorescence, what is the most likely diagnosis?

Goodpasture Syndrome (Anti-GBM Disease)

The most likely diagnosis is E) Goodpasture syndrome (anti-GBM disease), based on the pathognomonic finding of linear immunofluorescence on kidney biopsy combined with the pulmonary-renal syndrome presentation.

Clinical Reasoning

This 33-year-old man presents with the classic triad that defines pulmonary-renal syndrome:

• Hemoptysis (alveolar hemorrhage)
• Rapidly progressive glomerulonephritis (oliguria, hematuria with RBC casts, proteinuria)
• Acute kidney injury (oliguria for 48 hours)

The linear immunofluorescence pattern on kidney biopsy is pathognomonic for anti-GBM disease (Goodpasture syndrome). This represents IgG antibodies deposited in a continuous linear pattern along the glomerular basement membrane 1, 2.

Why Other Options Are Incorrect

• IgA nephropathy (A): Shows granular (not linear) IgA deposits on immunofluorescence, typically presents with episodic gross hematuria following upper respiratory infections, and does not cause pulmonary hemorrhage 2

• Minimal change disease (B): Presents with nephrotic syndrome (heavy proteinuria, hypoalbuminemia, edema) without hematuria or RBC casts, and shows no immunofluorescence deposits 3

• Temporal arteritis (C): A large-vessel vasculitis affecting elderly patients (typically >50 years), causing headache, jaw claudication, and vision loss—not pulmonary-renal syndrome

• Membranous glomerulopathy (D): Presents with nephrotic syndrome, shows granular (not linear) immunofluorescence with subepithelial deposits, and does not cause pulmonary hemorrhage 4

Diagnostic Confirmation

The kidney biopsy findings in anti-GBM disease include 2:

• Light microscopy: Crescentic glomerulonephritis (often >50% crescents)
• Immunofluorescence: Linear IgG deposition along GBM (the defining feature)
• Electron microscopy: No electron-dense deposits (distinguishes from immune complex disease)

Serum anti-GBM antibodies confirm the diagnosis in >90% of cases, though their absence does not exclude the disease when biopsy shows characteristic linear staining 5, 6.

Critical Management Points

This is a nephrological emergency requiring immediate treatment 3, 2:

1. Plasmapheresis should be initiated urgently (60 mL/kg volume replacement, daily treatments until bleeding stops, then every other day for 7-10 total treatments) 3

2. High-dose corticosteroids (pulse methylprednisolone 500-1000 mg IV daily for 3 days, then oral prednisone 1 mg/kg/day) 3

3. Cyclophosphamide (2 mg/kg/day orally or IV pulse therapy) 3

Treatment must begin immediately—even before serologic confirmation—because delay results in irreversible renal failure. Patients requiring dialysis at presentation rarely recover renal function 5, 2.

Common Pitfall

Do not wait for anti-GBM antibody results before initiating treatment. The linear immunofluorescence pattern on biopsy is sufficient to diagnose anti-GBM disease and begin aggressive therapy 6. Prognosis directly correlates with serum creatinine at presentation and speed of treatment initiation—patients with creatinine >5-6 mg/dL at diagnosis rarely recover renal function despite treatment 2.