Antiglomerular Basement Membrane Disease.

Antiglomerular basement membrane (anti-GBM) disease is a rare but life-threatening autoimmune vasculitis that is characterized by the development of pathogenic autoantibodies to type IV collagen antigens expressed in the glomerular and alveolar basement membranes. Once deposited in tissue, these autoantibodies incite a local capillaritis which manifests as rapidly progressive glomerulonephritis (GN) in 80 to 90% of patients, and with concurrent alveolar hemorrhage in ∼50%. A small proportion of cases may present with pulmonary disease in isolation. Serological testing for anti-GBM antibodies may facilitate rapid diagnosis, though renal biopsy is often required to confirm the presence of necrotizing or crescentic GN and linear deposition of autoantibody on the glomerular basement membrane. Alveolar hemorrhage may be evident clinically, or detected on imaging, pulmonary function testing, or bronchoscopy. Prompt treatment with plasmapheresis, cyclophosphamide, and steroids is usually indicated to remove pathogenic autoantibodies, to prevent their ongoing production, and to ameliorate end-organ inflammation. Alveolar hemorrhage is usually responsive to this treatment, and long-term respiratory sequelae are uncommon. Renal prognosis is more variable, though with aggressive treatment, independent renal function is maintained at 1 year in more than 80% of patients not requiring renal replacement therapy at presentation. Relapse in uncommon in anti-GBM disease, unless there is a concomitant antineutrophil cytoplasm antibody (present in 30-40%), in which case maintenance immunosuppression is recommended.