Glomerulonephritis (actually glomerulitis) is an inflammation of the glomeruli (kidney filters, part of the 1.2 million nephrons of each kidney). Chronic glomerulonephritis, which eventually leads to glomerulosclerosis, represents the main cause of dialysis-dependent kidney failure. In autoimmune glomerulonephritis autoantibodies are directed against the basement membrane of the kidney glomeruli (GBM antigens). Anti-GBM glomerulonephritis accounts for 0.5 to 2% of all glomerulonephritides.
Goodpasture's syndrome (pulmonary-renal syndrome) is a special form of autoimmune glomerulonephritis named after the US American pathologist Ernest William Goodpasture (1886-1960), who in 1919 described the combination of glomerulonephritis with pulmonary haemorrhage. This rare syndrome affects men six times more often than women, and predominantly those in young adulthood. It is clinically characterised by the combination of rapid progressive anti-basement membrane glomerulonephritis and pulmonary haemosiderosis, whereby pulmonary haemorrhage often occurs as the first sign.
The primary target antigen of all anti-GBM glomerulonephritides, including the classic Goodpasture's syndrome, is the NC1 region of the alpha-3 chain of the network-structured type IV collagen of the basement membrane lamina densa. These autoantibodies, which can be detected qualitatively or quantitatively in IIFT and quantitatively in the Anti-GBM ELISA, can be directed against the alveolar basement membrane or against the glomerular basement membrane. In cases without lung involvement GBM antibodies are detected in the serum or plasma of over 60% of patients, in cases with lung involvement in over 90%. They are predominantly of class IgG, more rarely of class IgA and IgM. Clinical progression of the disease correlates with antibody concentration. High-titer circulating GBM antibodies indicate an unfavourable progression. With a negative serum result and continuing suspicion of anti-GBM glomerulonephritis, a kidney biopsy should be performed.
Patients with mit Anti-GBM glomerulonephritides are often also ANCA positive (>35%). Positive results can indicate rapid-progressive glomerulonephritis or GPA. Therefore, parallel analysis of ANCA and Anti-GBM antibodies is recommended in patients with ANCA-associated vasculitis (AAV) with renal involvement.