Anti-GBM Disease
A life-threatening autoimmune disorder where antibodies attack the lungs and kidneys, causing pulmonary hemorrhage (coughing up blood) and rapidly progressive renal failure.
Emergency Management: Massive pulmonary hemorrhage causing asphyxia. Requires immediate intubation, mechanical ventilation with high PEEP to tamponade the bleeding capillaries, and emergency initiation of plasmapheresis.
Anti-Glomerular Basement Membrane (Anti-GBM) disease is a rare, life-threatening small vessel vasculitis caused by autoantibodies directed against the type IV collagen present in both the glomerular and alveolar basement membranes. It classically presents as rapidly progressive glomerulonephritis (RPGN) accompanied by alveolar hemorrhage.
Detailed Overview
The disease has a bimodal age distribution, affecting young men (who typically present with both pulmonary and renal symptoms) and older adults (predominantly renal involvement). The autoantibodies target the NC1 domain of the alpha-3 chain of type IV collagen. Binding of these antibodies triggers complement activation and severe tissue destruction. If left untreated, renal failure is rapid and irreversible, and massive pulmonary hemorrhage can be rapidly fatal. Prompt initiation of immunosuppression and plasmapheresis is limb- and life-saving.
Epidemiology & Demographics
Extremely rare, incidence of 1 per million patient-years. Bimodal distribution: peak in 20s-30s (predominantly males, prominent lung involvement) and 60s-70s (predominantly females, primarily kidney involvement).
Etiological Mechanism
Caused by the formation of IgG autoantibodies against the non-collagenous (NC1) domain of the alpha-3 chain of Type IV collagen [α3(IV)NC1].
Primary Causes
The exact trigger for autoantibody formation is unknown, but structural damage to alveolar capillaries exposes the normally hidden basement membrane antigens to the immune system. Strong genetic association with HLA-DR15.
Pathogenic IgG autoantibodies bind to the exposed α3(IV)NC1 domain in the alveoli and glomeruli. This activates the classical complement cascade and recruits neutrophils and macrophages. In the kidney, this intense inflammation ruptures the glomerular capillary loops, allowing fibrin to leak into Bowman's space, stimulating parietal epithelial cells and macrophages to form characteristic cellular 'crescents' (crescentic glomerulonephritis). This obliterates the glomerulus, causing rapid loss of renal function.
Diagnostic Criteria & Guidelines
Diagnosis is confirmed by the detection of circulating anti-GBM antibodies via ELISA or Western blot, AND confirmation of linear IgG deposition along the glomerular basement membrane on renal biopsy.
An aggressive 3-pronged approach is standard. 1) Plasmapheresis (daily for 14 days or until anti-GBM titers fall) to remove circulating antibodies. 2) Cyclophosphamide 2 mg/kg PO daily for 2-3 months to stop antibody production. 3) Pulse Corticosteroids: Methylprednisolone 1,000 mg IV daily for 3 days, followed by oral Prednisone 1 mg/kg/day with a slow taper over 6 months.
Second-Line & Adjunctive Therapy
Rituximab 375 mg/m2 IV weekly for 4 weeks can be used as an alternative to cyclophosphamide in patients with toxicity concerns or refractory disease. For severe hypoxemic respiratory failure due to hemorrhage, immediate intubation and mechanical ventilation are required.
Surgical & Procedural Management
Renal transplantation for patients who progress to End-Stage Renal Disease. Importantly, transplantation must be delayed for at least 6 months AFTER anti-GBM antibodies have been undetectable to prevent destruction of the new kidney.
Patient Counseling & Advice
Warn patients that while the pulmonary hemorrhage usually resolves completely with treatment, renal damage is often permanent and may require lifelong dialysis.
Follow-Up & Monitoring Schedule
Weekly monitoring of anti-GBM titers, serum creatinine, and complete blood counts during the acute phase. Cyclophosphamide therapy requires strict monitoring for leukopenia and hemorrhagic cystitis.
Preventive Strategies
No primary prevention exists. Relapses are rare (<5%) unlike ANCA vasculitis, so maintenance immunosuppression is usually discontinued after 3-6 months once titers are negative.
Survival has improved from <10% to >80% with plasmapheresis and immunosuppression. However, patients presenting with a creatinine > 5.7 mg/dL, or requiring immediate dialysis, rarely recover independent renal function.