anti-GBM disease

Anti-glomerular basement membrane (anti-GBM) disease is an autoimmune disorder characterized by circulating antibodies directed against the alpha-3 chain of type IV collagen (Goodpasture antigen) found in glomerular and alveolar basement membranes. The pathophysiology involves molecular mimicry or exposure of cryptic epitopes following basement membrane injury, leading to antibody formation and subsequent complement-mediated tissue damage. Clinically, it presents as rapidly progressive glomerulonephritis (RPGN) with crescent formation on kidney biopsy, often accompanied by acute kidney injury, hematuria, and proteinuria. When pulmonary involvement occurs (60-80% of cases), it manifests as pulmonary hemorrhage with hemoptysis, creating the classic Goodpasture syndrome. The disease shows a bimodal age distribution (peaks in 20s and 60s) with male predominance in younger patients. Diagnosis relies on detecting anti-GBM antibodies in serum (highly specific) and linear IgG deposition along the GBM on immunofluorescence microscopy. Treatment requires urgent plasmapheresis to remove circulating antibodies combined with high-dose corticosteroids and cyclophosphamide for immunosuppression. Prognosis depends on the degree of kidney function at presentation; patients with creatinine >6-7 mg/dL or requiring dialysis at diagnosis rarely recover kidney function.