Definition
Anti-glomerular basement membrane (anti-GBM) disease — historically Goodpasture syndrome when both lung and kidney are involved — is a small-vessel autoimmune disease caused by antibodies against the α3 chain of type IV collagen in basement membranes.
Pathophysiology
Autoantibodies bind the shared antigen in the glomerular and alveolar basement membranes, triggering complement-mediated injury. This produces a rapidly progressive (crescentic) glomerulonephritis and alveolar haemorrhage. There is a classic bimodal age distribution; pulmonary involvement is commoner in smokers.
Clinical presentation
- Renal: rapidly progressive glomerulonephritis — oliguria, haematuria, rising creatinine over days
- Pulmonary: haemoptysis, dyspnoea and diffuse alveolar haemorrhage
- Malaise, and features of anaemia from lung bleeding
Investigations
- Anti-GBM antibodies in serum (a subset are also ANCA-positive)
- Renal biopsy: crescentic glomerulonephritis with linear IgG deposition along the GBM on immunofluorescence
- Chest imaging: alveolar shadowing; a raised transfer factor (KCO) reflects intra-alveolar blood
Management
- Plasma exchange (plasmapheresis) to remove circulating antibody — the key intervention
- Corticosteroids and cyclophosphamide to suppress antibody production
- Supportive care; dialysis if required. Speed matters — dialysis-dependence at presentation predicts poor renal recovery
MRCP-specific traps
- Distinguish the three biopsy patterns: linear IgG (anti-GBM), granular immune-complex (e.g. lupus, post-infectious), and pauci-immune (ANCA vasculitis).
- Pulmonary haemorrhage is worsened by smoking and fluid overload.
- A minority are double-positive for anti-GBM and ANCA — such patients need treatment for both.
Summary
Anti-GBM disease is caused by antibodies to type IV collagen, producing crescentic glomerulonephritis and lung haemorrhage. Diagnosis is by serum anti-GBM antibodies and linear IgG on biopsy. Treat urgently with plasma exchange, steroids and cyclophosphamide.