Goodpasture Syndrome (Anti-GBM Disease)

Why Plasmapheresis, cyclophosphamide, and corticosteroids is correct

• The combination of diffuse alveolar hemorrhage and active glomerulonephritis (red blood cell casts, proteinuria) with a markedly elevated anti-GBM titer and negative ANCA establishes anti-GBM (Goodpasture) disease.
• Pathogenic circulating anti-GBM antibodies target type IV collagen in alveolar and glomerular basement membranes, so they should be rapidly removed.
• Plasmapheresis clears the circulating antibody, cyclophosphamide suppresses ongoing antibody production, and high-dose corticosteroids control inflammation — all three together are the standard induction regimen for active disease.
• Starting treatment urgently can preserve renal function and prevent dialysis dependence.

Why the others are wrong

• Rituximab, cyclophosphamide, and corticosteroids — Omits plasma exchange, so circulating pathogenic antibody is not rapidly cleared while alveolar hemorrhage and glomerular injury continue; rituximab is an ANCA-vasculitis/refractory option, not first-line anti-GBM induction (confused-with-ANCA-vasculitis).
• Cyclophosphamide and intravenous methylprednisolone — Uses correct immunosuppression but no plasmapheresis; drug therapy alone cannot clear circulating antibody quickly enough to halt alveolar hemorrhage and glomerular injury (right-drugs-wrong-omission).
• Mycophenolate, plasmapheresis, and corticosteroids — Keeps plasma exchange and steroids but swaps in mycophenolate, a standard lupus nephritis induction agent; KDIGO 2021 (Rec 11.2.1) pairs plasma exchange and glucocorticoids with cyclophosphamide for anti-GBM disease. Nothing here (intolerance, refusal, refractory disease) justifies a less-proven substitute during active alveolar hemorrhage, even out of toxicity or fertility concern in a young man (carrying over the lupus nephritis regimen).
• Intravenous immunoglobulin and corticosteroids — IVIG can stand in for plasma exchange in some antibody-mediated disorders, such as Guillain-Barre syndrome or myasthenic crisis, which is why it tempts, but it does not rapidly clear circulating anti-GBM antibody or stop its production, and KDIGO 2021 pairs plasma exchange and glucocorticoids with cyclophosphamide for anti-GBM disease (the trap is assuming IVIG and plasma exchange are interchangeable).

Additional high-yield points

• Plasma exchange remains standard in anti-GBM disease even though its routine use has narrowed in ANCA-associated vasculitis. KDIGO 2021 recommends the full regimen for all patients except those who are dialysis-dependent at presentation with 100% crescents or >50% global sclerosis on biopsy and no pulmonary hemorrhage, so alveolar hemorrhage always warrants full treatment.

Why Linear IgG deposition along the glomerular basement membrane is correct

• Anti-GBM disease is driven by IgG autoantibodies against the NC1 domain of the alpha-3 chain of type IV collagen, which binds continuously along the glomerular basement membrane.
• On immunofluorescence this produces a smooth, ribbon-like (linear) IgG pattern, often with C3 — the diagnostic hallmark that, combined with crescentic glomerulonephritis on light microscopy, confirms the diagnosis.
• The clinical picture (young smoker with alveolar hemorrhage plus rapidly progressive glomerulonephritis) is classic, and a positive serum anti-GBM antibody supports it, but linear IgG on biopsy is the defining finding.

Why the others are wrong

• Granular immune-complex deposits along glomerular capillary walls — this is the signature of immune-complex glomerulonephritis such as lupus nephritis (the "full-house" pattern of IgG, IgA, IgM, C3, and C1q); it is granular rather than linear and is accompanied by positive ANA/anti-dsDNA.
• Pauci-immune crescentic glomerulonephritis with scant deposits — this is the pattern of ANCA-associated vasculitis (GPA/MPA); both diseases cause rapidly progressive glomerulonephritis, but ANCA vasculitis shows little or no immunofluorescence staining rather than linear IgG. About 30% of anti-GBM patients are also ANCA-positive, so ANCA is always checked.
• IgA-dominant immune-complex deposits within the mesangium — this is the finding in IgA nephropathy or IgA vasculitis (Henoch-Schönlein), which presents with hematuria and, in vasculitis, palpable purpura — not alveolar hemorrhage with linear GBM staining.
• Basket-weave splitting of the glomerular basement membrane — both conditions involve type IV collagen of the GBM, but basket-weave splitting and lamellation on electron microscopy is the hallmark of Alport syndrome, an inherited collagen defect that presents with hematuria, sensorineural hearing loss, and eye findings rather than antibody-mediated alveolar hemorrhage with rapidly progressive glomerulonephritis.