ANTIGLOMERULAR BASEMENT MEMBRANE DISEASE
Antiglomerular basement membrane diseases are characterized by autoantibodies to the glomerular basement membrane (antiGBM). They include Goodpasture’s syndrome and Goodpasture’s disease. The former disorder shows glomerulonephritis, pulmonary hemorrhage and the presence of circulating antibodies to glomerular basement membrane; the latter is similar, but without the lung involvement. Both diseases are now included under the more general heading of antiGBM disease. Tissue damage is caused by antiGBM antibodies binding to the glomerular basement membrane and activating complement. Complement-mediated inflammation then ensues. The symptoms of glomerulonephritis include proteinuria and hematuria and erythrocyte casts (Margin Note 5.3) are seen.
The binding of antibodies to alveolar membranes causes hemoptysis, that is, the coughing up of blood from the lungs and about 40% of patients experience chest pain. Hemorrhaging from the lungs may eventually lead to respiratory failure. There is some suggestion that the binding of antibodies to the alveolar basement membranes is facilitated by exposure to organic solvents, which increase the permeability of the alveolar capillaries. The incidence of antiGBM disease is rare, of the order of 0.5 cases per million in the UK. Unlike mostautoimmune disease, it shows a predominance in males, with younger males generally presenting with both lung and kidney involvement.
Antiglomerular basement membrane disease can be diagnosed from linear deposits of antiGBM antibodies, which can be visualized by immunofluorescence on a kidney biopsy. An early diagnosis is essential and treatment must be started immediately. Therapy involves removal of circulating antibodies by plasmapheresis and the administration of immunosuppressive drugs . The mortality rate for antiGBM disease is improving, and is currently at 10%, although most patients develop end stage renal disease. In the past, the disease was invariably fatal.